Performance information

• EFFECT OF ROAD AND EMBANKMENT NETWORK ON THE FLOOD INTENSITY OF HAOR BASIN, BANGLADESH　　　　　　　　　　　　　　　
  Sowmitra Das Shuvro; Junji Yagisawa
  Journal of JSCE Special issue (Hydraulic Engineering), Volume：13, Number：2, First page：24, Last page：29, Dec. 2025, [Reviewed], [Corresponding]
  English, Scientific journal
• Experimental Study of Scouring and Deposition Characteristics of Riprap at Embankment Toe Due to Overflow　　　　　　　　　　　　　　　
  Abu Raihan Mohammad Al-Biruni; Md Masum Billah; Junji Yagisawa
  GEOTECHNICS, Volume：4, Number：3, First page：773, Last page：785, Sep. 2024
  In this study, the effects of the grain size and gradation of riprap, the overtopping flow depth, and the downstream slope of the embankment on the scouring and deposition characteristics at the downstream toe of the embankment were investigated. For the experiment, three different downstream slopes (1:2, 1:3, and 1:4), three different overflow depths (1, 2, and 3 cm), and three different sizes of riprap particles (d50 of 16.41 mm, 8.48 mm, and 3.39 mm, herein referred to as coarse gravel, medium gravel, and granule, respectively) were used in the laboratory. The experimental results demonstrated that the scour depth and deposition height increased with increasing energy head for each downstream slope condition. Among the three particle sizes, coarse gravel shows the lowest scour depth and the highest deposition height. For the 1:2 slope, the coarse gravel particle size was 62% and 75% less resistant to scouring than the medium gravel and granule particles, respectively. For the 1:3 slope case, this was 31% and 46%, and for the 1:4 slope case, this was 39% and 49% less than the medium gravel and granule size particles, respectively.
  MDPI, English, Scientific journal
  DOI：https://doi.org/10.3390/geotechnics4030040
  DOI ID：10.3390/geotechnics4030040, eISSN：2673-7094, Web of Science ID：WOS:001323875200001
• Headcut Migration in Earthen Embankment Induced by Varying Sub-surface and Seepage State under Overflow　　　　　　　　　　　　　　　
  Md Masum Billah; Junji Yagisawa
  GEOTECHNICAL AND GEOLOGICAL ENGINEERING, Volume：41, Number：8, First page：4659, Last page：4676, Nov. 2023
  In this study, the effects of an erosion resistant (ER) layer underneath the embankment and the seepage state prior to overflow were investigated. In the model experiment, tracing the headcut location using an Radio Frequency Identification (RFID) system without stopping the overflow demonstrated that the existence of an ER layer has a significant effect on the headcut migration rate, with a decrease in depth to the ER layer from 4.5 to 1.5 cm, the migration speed increased considerably by 1.20-1.86 times that of the case without an ER layer. When prolonged immersion prior to overflow was allowed, with the increase in the intensity of seepage, the headcut migration rate also increased, and as time elapsed, the effect of ER layer became subservient, though the degree of dominance of the seepage throughout the overflow period is controlled by the ER layer position. Thus, seepage state during prolonged immersion and ER layer underneath embankment toe needs special design consideration.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s10706-023-02538-x
  DOI ID：10.1007/s10706-023-02538-x, ISSN：0960-3182, eISSN：1573-1529, Web of Science ID：WOS:001022143100002
• DEVELOPMENT OF A RIVERBED VARIATION MODULE TO PREDICT SAND COVER RATE FOR THE FORAGING HABITAT OF AYU FISH　　　　　　　　　　　　　　　
  MIZOGUCHI Yuta; USAMI Shohei; YAGISAWA Junji; ONODA Yukio; TASHIRO Takashi; MIYAGAWA Yukio; NAKAMURA Keigo
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Volume：77, Number：2, First page：I_559, Last page：I_564, 2021
  Sand cover rate (SCR) is an important factor to explain the foraging habitats of ayu (Plecoglossus altivelis). Hence, a module of riverbed variation in a gravel-bed river with bimodal sediments was developed. The module calculated SCR, and the changes in SCR were defined as being driven by sand transport in the form of a suspended load that is deposited on stones (e.g., cobbles or pebbles) and in the interstices of stones. The prediction accuracy was examined by comparing the calculated SCR with the SCR measured in the field. The results showed that the spatial pattern of sand deposition/erosion predicted by the module was almost close to the measured one, though the predicted SCR tended to be higher/lower than the measured value. Chronological changes in the SCR calculated by the module suggested that sand deposits started forming along shorelines after the peak of a flood and then expanded toward the centers of the flow in channels in the end stage.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejhe.77.2_i_559
  DOI ID：10.2208/jscejhe.77.2_i_559, eISSN：2185-467X, CiNii Articles ID：130008160137
• EFFECT OF HARD-ERODIBLE SOIL LAYER ON SCOUR AROUND EMBANKMENT TOE DUE TO OVERTOPPING FLOW　　　　　　　　　　　　　　　
  NISHIKAWA Sakura; YAGISAWA Junji
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Volume：76, Number：2, First page：I_1165, Last page：I_1170, 2020
  At Typhoon No. 19 in 2019, at the site where the embankment was breached in Tokigawa River, it has been confirmed that a stratified soil layer was exposed around back side toe of embankment. The harderodible soil layer (here after HEL) may promote erosion in the upstream direction by preventing downward erosion, and may accelerate the time to breach. Therefore, the objective of this study is to clarify the effect of vertical position of HEL on local scouring around toe of embankment by hydraulic experiments.
  
   In the experiment, a total of 15 cases were carried out. By examining the residual sediment height, zi around the backside toe of embankment, the conditions under which erosion easily proceeds in the upstream direction were elucidated. As results of the experiment, it was found that the residual soil height ratio, zi/^zwo became smaller as the installation height of HEL became shallower. In the case where the height of the HEL is 1/4 ^zwo and 2/4 ^zwo, zi/^zwo became minimum when h1/H is 0.175.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejhe.76.2_i_1165
  DOI ID：10.2208/jscejhe.76.2_i_1165, eISSN：2185-467X, CiNii Articles ID：130008122547
• Tsunami mitigation by combination of coastal vegetation and a backward-facing step　　　　　　　　　　　　　　　
  Ghufran Ahmed Pasha; Norio Tanaka; Junji Yagisawa; Fuadi Noor Achmad
  Coastal Engineering Journal, Volume：60, Number：1, First page：104, Last page：125, 2018
  Since the 2011 Great East Japan tsunami, many improvements have been made in both hard and soft solutions for tsunami mitigation. After the 2011 Great East Japan tsunami, a post-tsunami survey was conducted along the coast in Miyagi Prefecture, which was one of the most tsunami-affected sites because rapid acceleration of the tsunami currents broke and washed away the trees, resulting in extensive damage to inland houses. In contrast, some of the houses located inland and away from vegetation with a dropping step survived. This shows a possibility that a step combined with the vegetation offers greater tsunami energy reduction by providing additional resistance. Laboratory experiments were conducted to investigate the energy reduction through a compound defense system (vegetation and a backward-facing step). Vegetation with a step (VS) showed greater energy reduction compared to that of only vegetation without a step (OV) due to additional loss by collision with the bed surface. However, the relative energy reduction in OV remained almost constant with the increase in the initial Froude number (F0, where the Froude number is obtained from a model without vegetation in a flume), whereas the relative energy reduction in VS showed a decreasing trend with increasing F0 because the energy reduction due to collision decreases with increase in water depth or F0.
  Taylor and Francis Ltd., English, Scientific journal
  DOI：https://doi.org/10.1080/21664250.2018.1437014
  DOI ID：10.1080/21664250.2018.1437014, ISSN：1793-6292, eISSN：1793-6292, SCOPUS ID：85058053571, Web of Science ID：WOS:000432689400008
• Effect of Submergence Condition and Overtopping Depth on Gully Scour Dimensions: Observations from the 2011 Great East Japan Tsunami　　　　　　　　　　　　　　　
  Sazia Afreen; Junji Yagisawa; Norio Tanaka
  JOURNAL OF EARTHQUAKE AND TSUNAMI, Volume：11, Number：2, Jun. 2017, [Reviewed]
  When a tsunami reaches a shore, it propagates along river channels with tremendous energy and overtops river levees. It causes severe damage to the levee structures through scouring along levee slope. In the present study, gully scours created along the levee slopes of two rivers (Omotogawa and Sakarigawa Rivers) in Iwate Prefecture and three rivers (Nanakitagawa, New Kitakamigawa, and Abukumagawa Rivers) in Miyagi Prefecture were investigated after the 2011 Great East Japan tsunami. The energy head during levee overtopping for each location was calculated from post-tsunami surveys. The relationship between the energy head and gully scour dimensions (length, width, and depth) was analyzed. The analyses clarified that gully scour dimensions were greatly dominated by two important phenomena: (i) overflow type (free overflow or submerged overflow), and (ii) soil texture at the scoured region. The present study results can be utilized to obtain the overtopping flow height for post-tsunami analysis.
  WORLD SCIENTIFIC PUBL CO PTE LTD, English, Scientific journal
  DOI：https://doi.org/10.1142/S1793431117500014
  DOI ID：10.1142/S1793431117500014, ISSN：1793-4311, eISSN：1793-7116, Web of Science ID：WOS:000401142700004
• NUMERICAL STUDY ON OPTIMUM ROUTE OF EVACUATION ASSISTANCE BUS BASED ON FLOOD INUNDATION MODEL FOR KAWAJIMA TOWN　　　　　　　　　　　　　　　
  YAGISAWA Junji; OKUBO Kazuaki; TANAKA Norio; AKASAKI Yuta
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Volume：61, Number：4, First page：Ⅰ_313, Last page：318, 2017
  Numerical simulation model which can analyze flood flow in rivers and flood inundation inland region in integrally was developed and it was applied to the Arakawa River basin including Kawajima town. The flood inundation characteristics (inundation direction and time to reach at each primary evacuation site (here after PES)) were elucidated considering two inundation conditions (overtopping occurs from Ichinogawa river (Case A) and Tokigawa river (Case B)). The big difference for the inundation direction can be confirmed between Case A (from north to southeastern) and B (from northwest to southeastern).
   Based on result of flood inundation model, optimum route of evacuation assistance bus was calculated for each inundation type. For Case A, to go around the western PES before overtopping and the eastern PES after overtopping minimized total evacuation time. In contrast, for Case B, to go around the northern PES firstly and the southern PES secondly was optimum for reducing total evacuation time. This result indicates that inundation characteristics should be clarified for proposing effective evacuation plan.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejhe.73.i_313
  DOI ID：10.2208/jscejhe.73.i_313, ISSN：1880-8751, eISSN：2185-467X, CiNii Articles ID：40021162462, CiNii Books ID：AN10426673
• FIELD OBSERVATION AND FLUME EXPERIMENT ON SAND TRANSPORTATION AT NAMIITA COAST　　　　　　　　　　　　　　　
  YAGISAWA Junji; TAKEMURA Takeshi; ONO Shotaro; ITABASHI Naoki; SHINOJIMA Kenichi; SUZUKI Junpei; TANAKA Norio
  Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), Volume：72, Number：2, First page：I_187, Last page：I_192, 2016
   For elucidating the sand movement characteristics at Namiita coast, in situ and flume experiments were conducted. Field experiments which used colored sand were conducted from Dec. 2014 to Feb. 2015 and from July - Oct. 2015. For both seasons, colored sand (d₅₀=0.6 and 1.0mm) has been confirmed to move not only offing direction (within the shallow region from the critical water depth for the sediment movement) but also shore direction from the setting point. If similar material will be used for the beach nourishment, there is a possibility to contribute to the re-formation of sandy beach.
   Flume experiments with considering different submarine topography (before and after 2011 Tsunami) and wave conditions were conducted. By using experimental results, change of submarine topography through the year was clarified. Even submarine topography after 2011 Tsunami, a tendency of sedimentation was confirmed to be maintained around beach line. These results suggest that sandy beach in Namiita coast might be reformed by conducting beach nourishment.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejoe.72.I_187
  DOI ID：10.2208/jscejoe.72.I_187, eISSN：2185-4688, CiNii Articles ID：130005263266
• STUDY ON CONDITIONS OF LEVEE BREACH DUE TO OVERFLOW EROSION BASED ON DATABASE OF FIELD MEASUREMENT　　　　　　　　　　　　　　　
  HATTORI Taito; NIHEI Yasuo; OHTSUKI Kazuaki; YAGISAWA Junji
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Volume：71, Number：4, First page：I_1285, Last page：I_1290, 2015
  Levee breaches occurred at a lot of rivers mainly due to overflow of extreme flood. However it is not clear what hydraulic and material conditions can cause failures of conventional levees or not due to the lack of field data on levee failures. In the present study, we conducted field surveys for levee failures due to overflow erosion and made database of the levee failures. In the field surveys, we collected hydraulic conditions like overflow depth, failure conditions and size of levees. The results indicated that 1) the levee breach appeared at overflow depth more than 0.5m, corresponding to the previous studies, and 2) degree of the levee damages was not appreciably related to the covering conditions of top and slopes of levees.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejhe.71.i_1285
  DOI：https://doi.org/10.2208/jscejcei.73.i_53_references_DOI_2uP1Oixs4WypQqvlAO2OWQiNFKV
  DOI ID：10.2208/jscejhe.71.i_1285, ISSN：1880-8751, eISSN：2185-467X, CiNii Articles ID：130005123444, CiNii Books ID：AN10426673
• Geometrical characteristic of scour holes caused by overtopping flow of embankment covered with different lengths of protection works
  八木澤 順治
  Volume：71, 2015, [Reviewed]
  Scientific journal
• Investigation of scouur pattern downstream of levee toe due to overtopping flow
  八木澤 順治
  Volume：71, 2015, [Reviewed]
  Scientific journal
• Return period of flood disturbance that increases diversity on gravel bars in middle stream of rivers　　　　　　　　　　　　　　　
  Kasun De Silva; Norio Tanaka; Junji Yagisawa
  LANDSCAPE AND ECOLOGICAL ENGINEERING, Volume：11, Number：1, First page：1, Last page：18, Jan. 2015, [Reviewed]
  Although medium-class flood disturbance is highly correlated with diversity of vegetated area of river habitat, it is still not clearly defined due to its complexity. To describe flood disturbance characteristics, two indices, breakage or overturning index and washout index, are used to express the breaking condition of trees and washout condition of trees and grasses. The relationship between diversity index of vegetated area (DI), calculated using vegetation species maps, and flood disturbance index (I (i) ), which represents the expected value of different flood disturbances, was investigated on four gravel bars in the Karasugawa River, Japan. The flood disturbance indices in Region A (high possibility to be a forest) and Region E (high possibility to be a bare area, as defined in this study) are identified as indicators for medium-class flood disturbance in this study. Moreover, this study confirms the results of previous studies on the Arakawa and Tamagawa Rivers, Japan, and their applicability to other rivers. In addition, the relationship between flood disturbance and DI in Region A or E explains the effect of flow regulation by construction of dams and weirs in river upstream on the downstream river habitat. Furthermore, based on the observed data and calculated results related to the possibility of vegetation and bare area on gravel bars in all investigated rivers, a range of flood return periods for medium-class flood disturbance for habitats on gravel bars was defined as 3-12.5 years, where the lower and upper values are related to the possibility of the presence of vegetation and the possibility of being a bare area, respectively.
  SPRINGER JAPAN KK, English, Scientific journal
  DOI：https://doi.org/10.1007/s11355-013-0229-4
  DOI ID：10.1007/s11355-013-0229-4, ISSN：1860-1871, eISSN：1860-188X, Web of Science ID：WOS:000349005200001
• Combined effects of coastal forest and sea embankment on reducing the washout region of houses in the Great East Japan tsunami　　　　　　　　　　　　　　　
  Norio Tanaka; Satoshi Yasuda; Kosuke Iimura; Junji Yagisawa
  JOURNAL OF HYDRO-ENVIRONMENT RESEARCH, Volume：8, Number：3, First page：270, Last page：280, Aug. 2014, [Reviewed]
  Coastal vegetation is widely recognized for its ability to reduce tsunami damage; however, coastal forests in large areas of the Tohoku and Kanto districts of Japan were destroyed by the Great East Japan tsunami on 11 March 2011. To elucidate the tsunami-mitigating effect of a coastal forest during a destructive tsunami, the combined effects of sea embankment and coastal forest were analyzed using post-tsunami survey data of the damage and a nonlinear long wave equation model that includes the breaking or washout condition of trees. The numerical simulations estimated that a 600-m-long coastal forest reduced the washout region of houses due to a 10-m-high tsunami at the coast by approximately 100 m, and the reduction achieved by a sea wall of approximately 5.4-6.4 m in height was approximately 560-1520 m, The height of a sea embankment or wall with sand dunes greatly affects the breaking condition of trees behind it by changing the tsunami flux overflowing the sea wall and the sand dune. For the combination of a sea embankment and a coastal forest during a destructive tsunami, the tsunami mitigation function of the coastal forest has an optimum value when the fluid force on the trees is strong but not strong enough to break the trees under the condition at which the tsunami overflows the sea embankment. At the investigated site, the effect of the coastal forest was larger than that of the sea embankment under optimal conditions. Thus, a coastal forest on a sand dune should be designed as a mitigation measure behind a sea embankment and optimally designed to protect the houses that are not protected from a tsunami by the sea embankment alone. (C) 2013 International Association for Hydro-environment Engineering and Research, Asia Pacific Division. Published by Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jher.2013.10.001
  DOI ID：10.1016/j.jher.2013.10.001, ISSN：1570-6443, eISSN：1876-4444, Web of Science ID：WOS:000345488000010
• METHOD FOR EVALUATING THE FORESTATION IN A RIVER CONSIDERING THE CHARACTERISTICS OF FLOOD DECLINE AND GEOMORPHOLOGY OF GRAVEL BARS ON THE DEPOSITION OF FINE SAND　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; OTSUKA Shohei
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Volume：70, Number：3, First page：60, Last page：70, 2014
  For clarifying the possibility of forestation in gravel bed bars or islands, sediment load change index (SLI) has been proposed considering deposition and washout of fine sand during flood discharge is declined. The applicability of this index was validated in the middle stream reach of the Oppe River, the Arakawa River and the Kanna River. Before and after typhoons in 2007, 2011 2012 and 2013, field investigations were conducted on six gravel bars in four rivers. River flow was also analyzed by two-dimensional depth-averaged Reynolds equations, and SLI was calculated. In comparison with SLI and sand deposition situation on the observed gravel bars, SLI has been found to express well the sand deposition situation on most of observed gravel bars. However, when this method is applied to the gravel bar which has small relative height from low channel and long distance along the flow direction, SLI could not express well the actual deposition situation. The effect of the excavation of gravel bar was investigated at Honda location in the Arakawa River through SLI. The re-colonization of the grass-type vegetation can be confirmed at the location where SLI becomes higher due to the excavation. This result indicates SLI is a suitable index for evaluating the effectiveness of the excavation of the gravel bar.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejhe.70.60
  DOI：https://doi.org/10.2208/journalofjsce.10.1_19_references_DOI_HaEyKnn9VgWdlUajsGOtLsc1iFA
  DOI ID：10.2208/jscejhe.70.60, eISSN：2185-467X, CiNii Articles ID：130004691650
• DYNAMIC GROWTH MODEL OF RIVER VEGETATION CONSIDERING THE CHANGE OF VEGETATION SUCCESSION SPEED DUE TO DEPOSITION OF FINE SAND　　　　　　　　　　　　　　　
  YAGISAWA Junji; TANAKA Norio
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Volume：70, Number：3, First page：71, Last page：81, 2014
  A dynamic model for predicting the long term change of vegetated area in river was developed when the flood does not change the morphology of the gravel bar. In this simulation model, the expansion, destruction due to floods and regeneration of the plants were considered. Change of vegetation succession speed was included in relation to the tendency of fine sand deposition due to floods. For elucidating the characteristics of deposition of fine sand due to floods, deposition situation after 2007 and 2012 flood events were investigated on the two gravel bars in the middle stream of Arakawa River.
   The simulation model was developed on a gravel bar located near Kumagaya Ohashi (KU) and applied to a gravel bar located near Arakawa Ohashi (AR) for validating the change of vegetated area from 2000 to 2012. This model expressed the situation of vegetated area in 2012 within the reasonable limit. Especially, this model can be found to describe not only the expansion location of each vegetation but also the vegetated area of each vegetation by considering change of vegetation succession due to deposition of fine sand by floods.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejhe.70.71
  DOI：https://doi.org/10.2208/jscejj.23-00264_references_DOI_RrbUZDBOxvGBCPB67wCRstIBHrd
  DOI ID：10.2208/jscejhe.70.71, eISSN：2185-467X, CiNii Articles ID：130004691651
• DRAG FORCE ACTING ON A QUADRATIC PRISM AND BED SHEAR STRESS AROUND IT IN SUPERCRITICAL FLOW　　　　　　　　　　　　　　　
  YAGISAWA Junji; TANAKA Norio
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Volume：69, Number：4, First page：I_685, Last page：I_690, 2013
  Many houses were broken and washed out by the supercritical tsunami flow overflowed from river embankment. Under the supercritical flow, drag force characteristics of dense obstacles and bed shear stress around them have not been clarified. Therefore, the objective of this study is to find out the effect of spacing of neighboring obstacles on the drag characteristics of quadratic prisms (house model) and bed shear stress distribution around them. Drag force acting on the house model and bed shear stress were measured by force gauge and shearing strain sensor, respectively. Four cases for different overflow depth and three cases for different G/bh (where, G and bh is horizontal spacing of each house model and width of a house model, respectively) were conducted. Drag force acting on the house model and bed shear stress between two house models (tm) increased with narrowing G. When G/bh=0.4, drag force and tm became 1.6 and 1.4 times comparing with single house model, respectively. However, when G/bh=1.2, drag force and shear stress became almost the same with single house case.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejhe.69.i_685
  DOI：https://doi.org/10.2208/jscejusr.78.1_1_references_DOI_P0vRW1Fj4XOXBiehimLeLCLrofi
  DOI ID：10.2208/jscejhe.69.i_685, eISSN：2185-467X, CiNii Articles ID：130004558043
• Effects of local scouring and saturation of soil due to flooding on maximum resistive bending moment for overturning Robinia pseudoacacia　　　　　　　　　　　　　　　
  M. B. Samarakoon; Norio Tanaka; Junji Yagisawa
  LANDSCAPE AND ECOLOGICAL ENGINEERING, Volume：9, Number：1, First page：11, Last page：25, Jan. 2013, [Reviewed]
  The effects on Robinia pseudoacacia (an exotic and invasive plant in Japanese rivers) of local scouring and saturation of the soil in the root-anchoring zone due to flooding were investigated. Scouring has been defined as the removal of substrate in the root-anchoring zone, exposing the tree roots. Tree-pulling experiments were conducted, simulating flood action, and the resulting damage was examined in order to assess the effect of local scouring on the maximum resistive bending moment (M (max)) for overturning. Scouring was artificially created to three different depths, 0, 25, and 50 cm. A nonlinear model was developed that included soil strength characteristics to calculate the critical overturning moment (M (cri)) under dry and saturated soil conditions. Significant correlations (p < 0.05) of M (max) with different tree and root-soil plate characteristics, such as diameter at breast height (D (bh)), tree weight, root depth, and root-soil plate radius, were developed in order to elucidate the effects of scouring on M (max). M (max) was slightly reduced with scouring depth for trees with D (bh) < 10 cm (small) trunks, and it was significantly and negatively (p < 0.05) correlated with scouring depth for trees with 10 < D (bh) < 20 cm (medium) trunks. However, M (max) did not change significantly with scouring depth for trees with a D (bh) > 20 cm (big) trunks. The nonlinear model was useful for determining the M (cri) of R. pseudoacacia under dry and saturated soil conditions. The overturning moments of all (small, medium, and big) trees were considerably reduced under the saturated soil condition. It could be concluded that medium-sized trees were greatly affected by scouring, and that small and big trees were mainly affected by saturation of the soil under severe flooding conditions.
  SPRINGER JAPAN KK, English, Scientific journal
  DOI：https://doi.org/10.1007/s11355-011-0169-9
  DOI ID：10.1007/s11355-011-0169-9, ISSN：1860-1871, eISSN：1860-188X, Web of Science ID：WOS:000313809900002
• Breaking pattern and critical breaking condition of Japanese pine trees on coastal sand dunes in huge tsunami caused by Great East Japan Earthquake　　　　　　　　　　　　　　　
  Norio Tanaka; Junji Yagisawa; Satoshi Yasuda
  NATURAL HAZARDS, Volume：65, Number：1, First page：423, Last page：442, Jan. 2013, [Reviewed]
  Coastal vegetation is widely recognized to reduce tsunami damage to people and buildings, and it has been studied recently because it requires relatively little capital investment compared with artificial measures, provides human-friendly beach fronts, and enhances inter-relationships with other ecological systems. However, the tsunami caused by the Great East Japan Earthquake at 14:46 JST on March 11, 2011, with a magnitude of 9.0 and epicenter 129 km east of Sendai, broke most of the sea wall (tsunami gates, large embankments) and caused catastrophic damage to coastal forests in the Tohoku and Kanto districts of Japan. A field survey was conducted to elucidate the critical breaking condition of Japanese coastal pine trees. Tree-trunk breakage was observed when the sea embankment was washed out or when there was no sea embankment and the tree was under strong inertia force or impact force by debris. Even though the trunk bending and breaking phenomena are different, statistical analysis showed that the critical diameters for trunk bending and trunk breaking were not very different. The overturning phenomenon is a little more complex than trunk breaking because the resistive force is a function of the substrate and root anchorage. An equation to determine the critical diameters for trunk bending, trunk breaking, and overturning was derived as a function of tsunami water depth, soil-root strength, and the hydrodynamic parameter (H (D) ) formulated by Froude number, drag coefficient, and the ratio of impact force to drag force considering the physical mechanisms to resist the tsunami. Trunk bending and breaking were closely related to tsunami water depth and the hydrodynamic parameter (H (D) ), but tree overturning was found to be more site specific, and the root-soil strength greatly affected the critical value. The proposed critical diameter equation and its coefficient are useful for the design of an inland forest of pine trees that can trap large trees, cars, debris, etc., to its breaking limit. The trapping function should be utilized more in the future designs of inland forests, if possible, on embankments.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11069-012-0373-4
  DOI ID：10.1007/s11069-012-0373-4, ISSN：0921-030X, eISSN：1573-0840, Web of Science ID：WOS:000312087100025
• EFFECTS OF UNDERSCOUR DEPTH AND HORIZONTAL SPACING BETWEEN TWO BED PROTECTION BLOCKS ON STABILITY OF FRONTAL BLOCK　　　　　　　　　　　　　　　
  Prem Shah; Norio Tanaka; Junji Yagisawa
  JOURNAL OF HYDRODYNAMICS, Volume：24, Number：4, First page：579, Last page：588, Sep. 2012, [Reviewed]
  The stability of a river-bed protection block in a flood event is affected by underscouring of the block. The effects of block spacing on block stability were investigated in different underscour conditions. Three blocks were placed at the bottom in a flume, and the underscour depth of the frontal block and distance between the first and second blocks were changed. Drag and lift forces were measured directly in each experimental condition. Particle Image Velocimetry (PIV) was used to visualize the flow and evaluate the streamline pattern. Pressure measurements around the block to understand the pressure distribution show that the pressure distribution on the rear and bottom surfaces of the block is significantly affected by changes in block spacing and underscour depth. The experimental results show that for the same underscour gap, lift, and drag coefficients decreased with increasing space between the two blocks. In addition, if the underscour gap is increased with the same horizontal spacing, the lift coefficient increases and drag coefficient decreases. These results demonstrate that wider spacing enhance stability of the frontal block in the underscour condition. Moreover, analysis of block stability with changing underscouring and horizontal spacing shows that bed protection blocks seem to have more stability when the gap between two bed protection blocks was equal to height of the blocks.
  ELSEVIER SCIENCE INC, English, Scientific journal
  DOI：https://doi.org/10.1016/S1001-6058(11)60280-1
  DOI ID：10.1016/S1001-6058(11)60280-1, ISSN：1001-6058, eISSN：1878-0342, Web of Science ID：WOS:000308803200013
• Effect of coastal forest and washout houses on the damage to houses by a tsunami　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; IIMURA Kosuke; KONDO Kota
  Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), Volume：68, Number：2, First page：I_301, Last page：I_305, 2012
  Coastal forests in large areas of the Tohoku and Kanto districts of Japan were destroyed by the tsunami after the Great East Japan Earthquake on 11 March 2011. A non-linear long wave model that includes the breaking and washout condition of trees and houses estimates the capacity of a coastal forest with 590m in width to reduce the moment of fluid force behind forest and the washout region of houses by around 110m. On the other hand, even the washed out sea embankment has been found to contribute for reducing the washout region of houses by 1520m. Washed out houses applied additional drag force on downstream houses, however it also reduces the washout region by 510m because of the resistance to tsunami current even after the houses were broken and floated.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/kaigan.68.i_301
  DOI ID：10.2208/kaigan.68.i_301, ISSN：1884-2399, eISSN：1883-8944, CiNii Articles ID：130004550783, CiNii Books ID：AA12508551
• Index of medium-class flood disturbance for increasing diversity of vegetation area at gravel bars or islands in middle of rivers　　　　　　　　　　　　　　　
  Norio Tanaka; Junji Yagisawa
  International Journal of River Basin Management, Volume：10, Number：3, First page：255, Last page：267, 2012, [Reviewed]
  To elucidate the relationship between biodiversity on gravel islands in a river and flood disturbance characteristics, wash-out conditions of trees and perennial grasses and breaking conditions of trees were analysed and the applicability of these indices was investigated. Two indexes are defined to express breaking and wash-out conditions of trees, breaking or overturning index (BOI) and wash-out index (WOI), respectively, and one index, WOI50, is used to express the removal condition of annual grasses. Using WOI, WOI50, and BOI, this study classified the habitats on gravel islands into five regions. The relationship between the diversity of vegetation area calculated by the vegetation species map in this study, and the flood disturbance index, a kind of probability expectation value of area for each region integrated from 2- to 40-year return periods of floods disturbance, was analysed on six gravel islands in the Arakawa and Tamagawa rivers. Within the five regions (Regions A-E), important trends were found for three regions. The diversity of vegetated areas in the gravel river habitat increased with increasing Id, the flood disturbance index in Region D, which expresses a flood disturbance that can break trees and move medium-size gravel. However, the diversity index has peak values for Ia and Ie, the flood disturbance indices in Regions A and E, respectively, where Ia can express the immobility of gravels and lack of damage to trees and Ie can express the mobility of large-size gravel and the wash-out condition of vegetation. The indices Ia and Ie may describe a medium-class disturbance to the habitat on gravel islands in the middle of a river. © 2012 International Association for Hydro-Environment Engineering and Research.
  TAYLOR & FRANCIS LTD, English, Scientific journal
  DOI：https://doi.org/10.1080/15715124.2012.681661
  DOI ID：10.1080/15715124.2012.681661, ISSN：1571-5124, eISSN：1814-2060, SCOPUS ID：84870362288, Web of Science ID：WOS:000212537000004
• Characteristics of damage due to tsunami propagation in river channels and overflow of their embankments in Great East Japan Earthquake　　　　　　　　　　　　　　　
  Norio Tanaka; Junji Yagisawa; Satoshi Yasuda
  International Journal of River Basin Management, Volume：10, Number：3, First page：269, Last page：279, 2012, [Reviewed]
  The tsunami caused by the Great East Japan Earthquake on 11 March 2011, with a magnitude of 9.0, broke most of the sea embankment and coastal vegetation belt and caused catastrophic damage to people and buildings in the Tohoku and Kanto regions of Japan. A field survey was conducted to elucidate the damage to river embankments and their hinterlands (residential area) by tsunami propagation in river channels and overtopping of embankments. Two, three, and four rivers in Iwate Pref., Miyagi Pref., and the Kanto region, respectively, were selected for the field investigation. In the hinterlands, the tsunami came from two directions, coast and river, and the situation, including the evacuation of people, became complex. Therefore, it is necessary to identify locations of river embankments that can be easily overtopped by a tsunami in different tsunami conditions. Tsunami inundation patterns were classified by the river capacity and whether a river or sea embankment was breached or not. This will provide useful information for making new hazard maps and planning new cities. © 2012 International Association for Hydro-Environment Engineering and Research.
  TAYLOR & FRANCIS LTD, English, Scientific journal
  DOI：https://doi.org/10.1080/15715124.2012.694365
  DOI ID：10.1080/15715124.2012.694365, ISSN：1571-5124, eISSN：1814-2060, SCOPUS ID：84870307329, Web of Science ID：WOS:000212537000005
• Effects of root architecture, physical tree characteristics, and soil shear strength on maximum resistive bending moment for overturning Salix babylonica and Juglans ailanthifolia　　　　　　　　　　　　　　　
  Norio Tanaka; M. B. Samarakoon; Junji Yagisawa
  LANDSCAPE AND ECOLOGICAL ENGINEERING, Volume：8, Number：1, First page：69, Last page：79, Jan. 2012, [Reviewed]
  Effects of root architecture, physical tree characteristics, and soil shear strength on overturning moment due to flooding were investigated using Salix babylonica and Juglans ailanthifolia, exotic and invasive plants in Japanese rivers. Tree-pulling experiments that simulated flood action were conducted, and the resulting damage was examined to assess the effects of physical tree characteristics and root architecture on the maximum resistive bending moment (M (max)) for overturning. In situ soil shear strength tests were conducted to measure soil strength parameters. The effects of species differences on the M (max) were examined by analyzing root architecture. S. babylonica has a heart-root system that produces a greater overturning moment due to the strong root anchorage and the large amount of substrate that must be mobilized during overturning. J. ailanthifolia has a plate-root system that produces a smaller overturning moment. However, trees with the plate-root system may withstand overturning better due to an increased root:shoot ratio. The results of the study show that the M (max) of a tree for overturning had significant (P < 0.05) correlations with a tree's physical characteristics, including height (H), trunk diameter at breast height (D (bh)), D (bh) (2) , height multiplied by the second power of D (bh) (trunk volume index H x D (bh) (2) ), and root-soil plate depth (R (d)), and root-soil plate radius (R (r)). Considering the strategy of J. ailanthifolia to increase the root:shoot ratio for anchoring in the substrate, the trunk volume index (H x D (bh) (2) ) is a better parameter than D (bh) (2) because it indirectly involves the difference in below-ground volume and surface area. Different soil cohesion values were found at different experimental sites, and the average M (max) for overturning each species decreased linearly with increasing soil cohesion.
  SPRINGER TOKYO, English, Scientific journal
  DOI：https://doi.org/10.1007/s11355-011-0151-6
  DOI ID：10.1007/s11355-011-0151-6, ISSN：1860-1871, Web of Science ID：WOS:000298610300007
• Estimation of drag coefficient of a real tree considering the vertical stand structure of trunk, branches, and leaves　　　　　　　　　　　　　　　
  Norio Tanaka; Hiroshi Takenaka; Junji Yagisawa; Taiji Morinaga
  International Journal of River Basin Management, Volume：9, Number：3-4, First page：221, Last page：230, 2011, [Reviewed]
  Drag coefficients of a real tree trunk and branch and the sheltering effects of an upstream trunk or branch on a downstream one in a linear arrangement with different spacings were investigated in detail. Willow and Robinia pseudoacacia, representative and invasive trees in Japanese rivers, respectively, were selected for the study. The drag coefficient of the real tree trunk started to decrease from a relatively low Reynolds number and was smaller than that of a smooth circular cylinder in the entire Reynolds number range investigated. Leaves increased the drag coefficient by around 40–100% in comparison to that of a branch alone and increased with increasing the area ratio of leaves and branches. The sheltering effects of an upstream branch increased with the existence of leaves. The drag coefficient of a downstream branch approached around 95% of that of a single branch with increasing Reynolds number, regardless of the presence of leaves. The moment for drag force of a whole tree was calculated for a strong wind event that overturned trees in the Arakawa River, Japan. The calculated value was compared with the experimental threshold values and was validated within a reasonable limit. © 2011 International Association for Hydro-Environment Engineering and Research.
  TAYLOR & FRANCIS LTD, English, Scientific journal
  DOI：https://doi.org/10.1080/15715124.2011.606427
  DOI ID：10.1080/15715124.2011.606427, ISSN：1814-2060, eISSN：1814-2060, SCOPUS ID：84859899881, Web of Science ID：WOS:000212533100007
• Flow structures and sedimentation characteristics around clump-type vegetation　　　　　　　　　　　　　　　
  Norio Tanaka; Junji Yagisawa
  JOURNAL OF HYDRO-ENVIRONMENT RESEARCH, Volume：4, Number：1, First page：15, Last page：25, Apr. 2010, [Reviewed]
  Models comprising 7, 19, 37, or 61 equally spaced circular cylinders in a staggered hexagon-shape arrangement were mounted on a water-flume bed, and the characteristics of flow structures in uniform flow around the models were investigated to elucidate the effects of number, density, and the emergent or submerged condition of the cylinders as a model of clump-type roughness. Drag force was measured with changing both the relative optical gap (G/D) and relative height (h/H), where G is the optical gap between neighboring cylinders in cross-section, D is the cylinder diameter, h is the model height, and H is the water depth, and the drag coefficient C-d was calculated. The flow structure around the clump-type roughness models and the drag coefficients changed greatly with changing G/D. The number of cylinders in the clump-type model greatly affected the value of C-d when G/D was large, because the sheltering effect is changed with the number. Flow structures changed around G/D >1. The C-d in the emergent condition became slightly larger than that in the submerged condition but was not much changed in comparison with the G/D. Sedimentation around and behind vegetation was investigated in the field after a flood event. When the vegetation density was high (G/D < 0.5-1), such as with willow (Sa subfragilis) or dense grass (Eragrostis curvula, a clump-type vegetation), sedimentation occurred behind the vegetation region. When the vegetation density was low (G/D > 1), such as with Robinia pseudoacacia or Phragmites japonica, it occured inside the vegetation region. The flume experiment and field study indicate that the flow pattern changes depending on the G/D with a wide range of Reynolds numbers and that it affects the sedimentation pattern at an actual flood event. (C) 2009 International Association for Hydro-environment Engineering and Research, Asia Pacific Division. Published by Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jher.2009.11.002
  DOI ID：10.1016/j.jher.2009.11.002, ISSN：1570-6443, eISSN：1876-4444, Web of Science ID：WOS:000281648600003
• Flood wash-out conditions of an exotic and invasive plant, Eragrostis curvula, in Arakawa River, Japan　　　　　　　　　　　　　　　
  Junji Yagisawa; Norio Tanaka
  International Journal of River Basin Management, Volume：8, Number：1, First page：15, Last page：24, Mar. 2010, [Reviewed]
  The effect of an exotic and invasive plant, Eragrostis curvula, on the threshold of gravel movement and wash-out conditions of the plant due to flood was investigated in the midstream Arakawa River, Japan. Under various hydraulic conditions (grain diameter, bed slope, and water depth) and plant growth characteristics (clump diameter and plant density), the Shields parameter of the gravel in the plant-vegetated area was estimated using the drag characteristics of the plant measured directly in field and wind tunnel experiments, and the plant's effect on friction velocity was evaluated. The removal threshold of E. curvula could be defined when the friction velocity around the plants was equal to the critical friction velocity of d84 grain diameter at which 84% volume passed through the sieve. The threshold condition was found to be well expressed by the relationship between the bed slope direction component of the water weight and the drag characteristics due to the plant MDc1.5, where M is the plant density and Dc the clump diameter of E. curvula. © 2010 International Association for Hydro-Environment Engineering and Research.
  TAYLOR & FRANCIS LTD, English, Scientific journal
  DOI：https://doi.org/10.1080/15715121003715057
  DOI ID：10.1080/15715121003715057, ISSN：1571-5124, eISSN：1814-2060, SCOPUS ID：77954852842, Web of Science ID：WOS:000212527900003
• METHOD FOR EVALUATING THE DYNAMICS OF FOREST IN RIVERS CONSIDERING TWO INDICES REPRESENTING THE BREAKING AND WASH-OUT CONDITIONS OF TREES ON GRAVEL-BED BARS　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; FUKUOKA Shoji
  Doboku Gakkai Ronbunshuu B, Volume：66, Number：4, First page：359, Last page：370, 2010
  For evaluating the possibility of forestation in gravel bed bars, Breakage or Overturning Index (BOI) and Wash-Out Index (WOI) were derived considering the difference of tree breaking phenomena due to floods, i.e. trunk breakage or overturning, and wash-out of trees, respectively in this study. Coupling the two indices, the method for classifying the river habitat into four, not breaking and not washout (Region A), breaking and not washout (Region B), not breaking and washout (Region C), and breaking and washout (Region D), is proposed. The applicability of the two indices, BOI and WOI, were validated in the middle stream reach of the Arakawa River and the down stream from the upper stream reach of the Tamagawa River. In addition, in seven locations where relative height from ordinary water level is different, the breaking modes of trees were classified in the BOI-WOI plot considering floods with different return periods. There are two patterns for the dynamics of plots with flood return period in the BOI-WOI figure. One is changed from Region A to Region D (Pattern I), and the second is changed from Region A to Region B (Pattern II). In Pattern II, trees are not washed out even though they are damaged. Then, the location has high possibility to be a stable forest. Therefore, the countermeasure for preventing the forestation should be considered to change the habitat from Pattern II to Pattern I.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.2208/jscejb.66.359
  DOI：https://doi.org/10.2208/jscejj.23-00264_references_DOI_ZjZHof5RltazodfDip0JRZp1OiA
  DOI ID：10.2208/jscejb.66.359, eISSN：1880-6031, CiNii Articles ID：130004468118
• FLOW STRUCTURES AND SEDIMENTATION CHARACTERISTICS AROUND COLONY-TYPE VEGETATION AT FLOOD EVENTS　　　　　　　　　　　　　　　
  Norio Tanaka; Shiho Ito; Junji Yagisawa
  ADVANCES IN WATER RESOURCES AND HYDRAULIC ENGINEERING, VOLS 1-6, First page：981, Last page：986, 2009, [Reviewed]
  Colony models, comprising seven equally spaced cylinders with staggered arrangement are mounted on a water flume bed. The characteristics of flow structures around the colony-type roughness model in uniform flow were investigated. For elucidating the effects of the vegetation density and emergent or submerged condition of the colony-type roughness according to the flood water depth, drag force is measured with changing both of the relative space L/d and the relative height h/H,where L is the space between neighbored cylinders, d is the cylinder diameter, h is the model height and H is the water depth and the drag coefficient (C(d)) is calculated. The flow structure around the colony models and the drag coefficients values are changed depending on L/d and h/H. Two types of flow structures, a large-scale Karman vortex street behind the colony models and a primitive Karman vortex street behind the individual cylinders are generated. The C(d) in emergent condition becomes larger than that in submerged condition. The C(d) increases sharply when h/H is ranged from 0.8 to 1.0 and then approaches the C(d) value in unsubmerged condition. In field observation, sedimentation around the two roughness type was investigated. When the vegetation density is large, like willow, i.e. Salix subfragilis or Eragrostis curvula (colony-type vegetation), the sedimentation is occurred behind the vegetatation region When vegetation denesity is small, it occurres inside the vegetation region, i.e., Robinia pseudo-acacia or Phragmites japonica. Similar flow structure are supposed to be occurred in water flume experiment and in field. This study elucidated the effect of vegetation density on flow structure.
  TSINGHUA UNIVERSITY PRESS, English, International conference proceedings
  DOI：https://doi.org/10.1007/978-3-540-89465-0_172
  DOI ID：10.1007/978-3-540-89465-0_172, Web of Science ID：WOS:000268750700172

• EFFECT OF HARD-ERODIBLE SOIL LAYER ON HEADCUT MIGRATION AND EMBANKMENT BODY DEFECT　　　　　　　　　　　　　　　
  西川 咲良; 八木澤 順治
  Advances in River Engineering, Volume：27, First page：211, Last page：216, 2021
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.27.0_211
  DOI ID：10.11532/river.27.0_211, eISSN：2436-6714, CiNii Articles ID：130008113990
• DEVELOPMENT OF PHYSICAL HABITAT SIMULATION MODEL FOR AYU CONSIDERING RIVERBED ENVIRONMENT IN CHANNEL WITH CONSTRASTING RIVERBED ENVIRONMENT　　　　　　　　　　　　　　　
  USAMI Shohei; YAGISAWA Junji; MIZOGUCHI Yuta; ONODA Yukio; TASHIRO Takashi; MIYAGAWA Yukio
  Advances in River Engineering, Volume：26, First page：361, Last page：366, 2020
  For the evaluation of habitat suitability for fish, hydraulic data that can be easily observed have been
  often used. However, it has become essential to consider fish's preference for riverbed environments
  modified by artificial sediment supply in gravel-bed rivers. In this study, two types of evaluation methods
  were applied on the target river with different riverbed environment in the two diversion channels. These
  models are conventional evaluation method based on hydraulic quantity (HSI), and it taking into account
  the sand cover on stony riverbed as a riverbed environment in addition to the hydraulic quantity (HSIb). The
  prediction accuracy was elucidated by comparing the habitat suitability index calculated from these models
  with the spatial distribution of the focal point of Ayu obtained from the field survey. The evaluation of
  habitat suitability taking into account the degree of sand coverage (HSIb) was found to be able to evaluate
  the focal point of Ayu more accurately than the conventional method (HSI).
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.26.0_361
  DOI ID：10.11532/river.26.0_361, eISSN：2436-6714
• THE EFFECT OF PERIODIC IRREGULARITIES AT THE CREST OF EMBANKMENT ON GULLY EROSION　　　　　　　　　　　　　　　
  YAGISAWA Junji; MASAMURA Ryota
  Advances in River Engineering, Volume：26, First page：497, Last page：502, 2020
  At Typhoon No.19 in 2019, overtopping flow from embankment occurred at many locations in the Arakawa River tributaries, and gully erosions have been confirmed. In a previous study, the relationship between the wavelength of irregularities at crest of embankment and gully erosion was examined by laboratory experiments. However, since this experiment was conducted with the overflow water depth limited, the effect of changes in overflow depth on gully erosion characteristics has not been clarified. Therefore, the objectives of this study are 1) to clarify the effect of increasing overflow depth on the gully erosion characteristics by hydraulic experiment, and 2) to confirm the similarity between gully erosion characteristics obtained by experiments and actual phenomena in the field. As a results of hydraulic experiment and field survey, it was confirmed that dimensionless erosion depth and interval of neighboring gully erosions were similar to the experimental values.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.26.0_497
  DOI ID：10.11532/river.26.0_497, eISSN：2436-6714
• PROPOSAL OF STANDARDIZED GUIDELINE FOR ON-SITE SURVEYS AND COMMON DATABASE FOR RIVER FLOOD DISASTERS　　　　　　　　　　　　　　　
  KURE Shuichi; OHTSUKI Kazuaki; YAGISAWA Junji; NAGANO Hiroyuki; NIHEI Yasuo
  Advances in River Engineering, Volume：23, First page：67, Last page：72, 2017
  The frequency and magnitude of the water-related disasters have been increasing all over the world. Several organizations including JSCE flood disaster investigation team generally conduct an on-site survey after severe disasters in order to clarify the damage mechanism. However, there is no solid guideline for the river flood disaster in Japan, whereas the tsunami disaster. This report provides essential information of a proposed guideline for standardization of an on-site field survey and data treatment for flood disaster. We especially focused on ways to identify inundation marks (depth or height) and to evaluate building damage and bank failure. For surveyor’s convenience and safety, the guideline includes concrete cases with many example photos and useful data sheets. The guideline also deals with a simple and fast data sharing method with Google My Map service, a tool for data combination of field data and photos developed on Excel VBA and secure data sharing method provided by JSCE.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.23.0_67
  DOI ID：10.11532/river.23.0_67, eISSN：2436-6714
• 水害調査方法の標準化に向けて : 家屋被害分類—Toward standardization of on-site surveys of river flood disasters : damage classification of residential houses　　　　　　　　　　　　　　　
  呉 修一; 八木澤 順治; 大槻 順朗
  Volume：52, First page：55, Last page：60, Mar. 2016
  Japanese
  CiNii Articles ID：40020760182, CiNii Books ID：AN00352457
• THE CAHARACTERISTICS OF LEVEE-BREACH PHENOMENA AND SCOURED REGION OF THE KINUGAWA RIVER AND SOME BRANCHES OF TONEGAWA RIVERS AT KANTO & TOHOKU HEAVY RAIN IN SEPTEMBER 2015　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; IGARASHI Yoshiya; YAMAGISHI Genya
  Advances in River Engineering, Volume：22, First page：333, Last page：338, 2016
  For clarifying the scoured characteristics around levee breaching point at the 2015 Kanto & Tohoku heavy rain, post flood survey was conducted not only for the Kinugawa River but other rivers in Ibaraki Prefecture where levee breaching was occurred, and the breaching length and the depth of the scoured region were investigated with the hydraulic parameters. Flume experiment was also conducted in a flume with 1/60 scale. The levee shape were selected as the full shape and the half-scoured levee shape. Clear water scour condition was set at the downstream of the levee. The number of scoured region for the full shape levee condition were around 5-8, and is similar to the actual situation at the breaching point of the Kinugawa River. The scoured depth for half scoured levee shape was 1.5-1.8 times larger for full-size embankment case. The breaching widths for Miyato, Nishinire, and Hachikenbori River, were relatively small, but was similar to the initial breaching width of the Kinugawa River.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.22.0_333
  DOI ID：10.11532/river.22.0_333, eISSN：2436-6714
• EVALUATION OF SUPPLIED-SEDIMENT DYNAMICS ON THE ARMORED BED IN THE DOWNSTREAM OF FUTASE-DAM RESERVOIR　　　　　　　　　　　　　　　
  TAKEZAWA Shota; TANAKA Norio; YAGISAWA Junji; HONDO Takumi
  Advances in River Engineering, Volume：21, First page：115, Last page：120, 2015
  For improving river environment, artificial sand supply is recently conducted in downstream of dam reservoirs. However, there are many unknowns regarding how the sediment supply affects the bed material size and its dynamics at a flood event. Therefore, the purpose of this study is to clarify quantitatively the dynamics of artificial supplied sand in armored bed by proposing new model for calculating bed shear stress in the cobble layer. Quasi-three dimensional model has been developed considering the sheltering effect by boulders and decrease of bed shear stress. 2D model and the quasi 3D model are compared at flood events in downstream of the Futase Dam. Dynamics of sedimentation height and the deposited mean diameter were analyzed in the simulation. The quasi 3D model can express well the sedimentation at an inner side of meandering part of the river. The size of deposited material in gravel layer is more than 4cm. The model has a possibility to express the dynamics of supplied sediment motion in armored rivers.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.21.0_115
  DOI ID：10.11532/river.21.0_115, eISSN：2436-6714
• STOCHASTIC ANALYSIS OF FORESTATION ON EXCAVETED GRAVEL BAR BY GROWTH DYNAMIC MODEL　　　　　　　　　　　　　　　
  YAGISAWA Junji; TANAKA Norio
  Advances in River Engineering, Volume：21, First page：319, Last page：324, 2015
  As one of the countermeasures for the forestation on gravel bars, excavation of gravel bars is recently conducted. To conduct effective excavation for preventing re-forestation during long term, stochastic analysis is needed considering various flow discharge condition. Therefore, objective of this study is to clarify the effect of forestation due to the excavation of the gravel bar. To fulfill the objective, the long term growth dynamic model was used for evaluating the possibility of forestation under various discharge condition. The developed model was applied to gravel bar at Honda in Arakawa River. Expected value of forestation (EV) was defined and its value was calculated in each excavation type. As a comparison of EV in each excavation type, EV value for Case 6 which gravel bar is excavated diagonally, becomes smallest. It is indicated that developed model can evaluate the suitable excavation type for preventing re-forestation on the gravel bar.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.21.0_319
  DOI ID：10.11532/river.21.0_319, eISSN：2436-6714
• METHOD FOR EVALUATING THE RE-FORESTATION OF EXCAVATED GRAVEL BAR CONSIDERING DEPOSITION AND WASHOUT OF FINE SAND　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; OTSUKA Shohei; HIRONO Futoshi; TAKESHIMA Makoto
  Advances in River Engineering, Volume：19, First page：387, Last page：392, 2013
  For clarifying the possibility of forestation in gravel bed bars or islands, sediment load change index (SLI) has been proposed considering deposition and washout of fine sand during flood discharge is declined. The applicability of this index was validated in the middle stream reach of the Oppe River and the Arakawa River. Before and after typhoons in 2007, 2011 and 2012, field investigations were conducted on five gravel bars in two rivers. River flow was also analyzed by two-dimensional depth-averaged Reynolds equations, and SLI was calculated. In comparison with SLI and sand deposition situation on observed gravel bars, SLI has been found to express well the sand deposition situation on most of observed gravel bars. However, when this method is applied to the gravel bar which has small relative height from low channel or long distance along the flow direction, SLI could not express well the actual deposition situation. The effect of the excavation of gravel bar was investigated at Honda location in the Arakawa River through SLI. The re-colonization of the grass-type vegetation can be confirmed at the location where SLI becomes higher due to the excavation. This result indicates SLI is suitable parameter for evaluating the effectiveness of the excavation of the gravel bar.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.19.0_387
  DOI ID：10.11532/river.19.0_387, eISSN：2436-6714
• DYNAMIC GROWTH MODEL OF RIVER VEGETATION CONSIDERING REGENERATION AND EXPANSION PROCESS OF TREES WITH CHANGING MAGNITUDE OF DESTRUCTION　　　　　　　　　　　　　　　
  YAGISAWA Junji; TANAKA Norio; FUKUOKA Shoji
  Advances in River Engineering, Volume：19, First page：393, Last page：398, 2013
  A dynamic model for predicting the long term change of vegetated area in river was developed when the flood does not change the morphology of the gravel bar. In this simulation model, the expansion, destruction due to floods and regeneration of the plants were considered. In this study, the wash-out of plants and tree trunk breakage were considered as the destruction mechanism of the river vegetation due to floods. For elucidating the characteristics of regeneration of tree type vegetation, tree regeneration situation after 1year of the 2006 and 2007 flood event was investigated in the Arakawa River. The simulation model was applied to the middle stream reach of the Arakawa River for validating the change of vegetated area from 2000 to 2012. This model expressed the situation of vegetated area in 2012 within the reasonable limit. Especially, this model can be found to describe the location of each vegetation and expansion area of woody type vegetation by considering the tree’s regeneration and expansion after the trunk bending or breaking damage by floods.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.19.0_393
  DOI ID：10.11532/river.19.0_393, eISSN：2436-6714
• APPLICABILITY OF QUASI-THREE DIMENSIONAL FLOW ANALYSIS CONSIDERING RIVER BED VARIATION AND WASHOUT AND BREAKING CONDITION DURING A FLOOD　　　　　　　　　　　　　　　
  MORINAGA Taiji; YAGISAWA Junji; TANAKA Norio; UCHIDA Tatsuhiko
  Advances in River Engineering, Volume：18, First page：77, Last page：82, 2012
  For the management of river channel, it is very important to estimate correctly the change of river bed topography at a flood event. However, the bed variation is quite difficult to predict for the river where forestation occurs because of the change of vegetation resistance during a flood. The new method is proposed in this study to evaluate the bed variation around a forest on a gravel bar at large flood event. River bed variation analysis was conducted for the middle stream region of Arakawa River using quasi-three dimensional flow model combined with the new method that includes the washout and breaking condition of trees. Observed amount of bed variation was reproduced well by the model considering the washout and breaking condition of trees during a flood. On the other hand, the difference is small on the calculated river bed variation between the quasi-three dimensional and two-dimensional method. This result indicates that the improvement of vegetation resistance change during a flood event is important for the accurate evaluation of river bed variation at a large flood event that can washout or break trees.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.18.0_77
  DOI ID：10.11532/river.18.0_77, eISSN：2436-6714
• TSUNAMI PROPAGATION IN RIVERS AND OVERTOPPING FROM RIVER EMBANKMENT AFTER THE GREAT EAST JAPAN EARTHQUAKE　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; SATO Masayuki; HOSOGAYA Yoh
  Advances in River Engineering, Volume：18, First page：357, Last page：362, 2012
  The tsunami caused by the Great Japan Earthquake on 11 March 2011, broke most of the sea embankment and coastal vegetation belt and caused catastrophic damage to people and buildings in the Tohoku and Kanto regions of Japan. Field surveys were conducted to elucidate the damage to river embankments and their hinterlands (residential area) by tsunami propagation in river channels and overtopping of embankments. Ten rivers were selected for the field investigation. In the hinterlands where overtopping occurred, the tsunami came from two directions, coast and river. It is necessary to identify locations of river embankments that can be easily overtopped by a tsunami in different tsunami conditions, river morphology and inland embankment of roads or trains. Tsunami inundation patterns were classified by the river capacity and whether a river or sea embankment was breached or not. This will provide useful information for making new hazard maps and planning new cities. Numerical simulation in Abukumagawa River shows the clear relationship between the scoured area and the tsunami overtopping time.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.18.0_357
  DOI ID：10.11532/river.18.0_357, eISSN：2436-6714
• METHOD FOR EVALUATING THE FORESTATION ON GRAVEL BARS IN RIVERS CONSIDERING SEDIMENT DEPOSITION INDEX　　　　　　　　　　　　　　　
  YAGISAWA Junji; TANAKA Norio; FUKUOKA Shoji
  Advances in River Engineering, Volume：18, First page：65, Last page：70, 2012
  For evaluating the possibility of forestation in gravel bed bars, sediment deposition index (SDI) was derived considering the characteristic of flood hydrograph. The applicability of this index was validated in the middle stream reach of the Oppe River and the down stream reach of the Tamagawa River. Before and after typhoon No.12 and 15 on 2011, field investigations were conducted on gravel bars in Tamagawa and Oppe River. For above two floods, river flow was analyzed by two-dimensional depth-averaged Reynolds equations, and SDI and WOI (Washout index proposed by Tanaka et al. (2010)) were calculated. Calculated SDI in numerical simulation and situation of sand deposition on observed gravel bars were compared. When the critical value of SDI was considered to be 0.7, SDI could express well the sand deposition situation on observed gravel bars. By using SDI-WOI plot, vegetated situation of grass type vegetation on gravel bars in Tamagawa River was classified well. Grass type vegetation has been found to grow only on where SDI is larger than 0.7 and WOI is smaller than 1.4. These results indicated SDI-WOI plot proposed in this study has some possibility to evaluate the location that grass type vegetation can grow easily.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.18.0_65
  DOI ID：10.11532/river.18.0_65, eISSN：2436-6714
• INDEX FOR EXPRESSIING VEGETATION BREAKAGE AND WASHOUT BY FLOOD DISTURBANCE AND HIGHLY CORRELATED WITH BIODIVERSITY ON GRAVEL-BED BARS　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; KIKUJI Yu; SATO Takanori; FUKUOKA Shouji
  Advances in River Engineering, Volume：17, First page：227, Last page：232, 2011
  For elucidating the relationship between flood disturbance and biodiversity of vegetation in gravel bed bars, Breakage or Overturning Index (BOI) and Wash-Out Index (WOI) were derived considering the difference of vegetation breaking phenomena due to floods, i.e. trunk breakage or overturning, and wash-out of trees or grass, respectively. Coupling the two indices, the method for classifying the river habitat into five, not tree breaking and not washout (Region A), tree breaking and not washout (Region B), not tree breaking and washout (annual grass) (Region C), tree breaking and washout (annual grass) (Region D), and washout of all vegetation (Region E), is proposed. The condition at which WOI is larger than 0.5, and WOI is less than one, is correlated with the Shannon-Wiener index at three gravel-bed bars in the Arakawa River, Japan. Especially, when BOI is larger than one, the biodiversity is increased. For Region A and E, the trend is assumed to be affected by the duration after flood. The proposed index for Region D has possibilities to express middle class disturbance that is closely related to the biodiversity at the habitat.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.17.0_227
  DOI ID：10.11532/river.17.0_227, eISSN：2436-6714
• EFFECTS OF SOIL SHEAR STRENGTH AND ROOT ARCHITECTURE ON MAXIMUM RESISTIVE BENDING MOMENT FOR OVERTURNING　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; SAMARAKOON Methsiri; SASAKI Yasushi; TONEGAWA Makoto
  Advances in River Engineering, Volume：第16巻, First page：225, Last page：230, 2010, [Reviewed]
  Tree pulling experiments that simulated flood action were conducted using Salix babylonica and Juglans ailanthifolia, exotic and invasive trees in Japanese rivers.. The resulting damage was examined in order to assess the effects of physical tree characteristics and root architecture on the maximum resistive bending moment (M_max) for overturning. In situ soil shear strength tests were conducted in order to measure soil strength parameters. Significantly correlated (p<0.05) non-linear relationships were found between M_max and tree characteristics, and H*D ² provided the best predictor of the Mwithin them. Non-linear models were fitted between M_max and D_bh for each species. The more efficient root architecture to withstand overturning is the heart-root system of S. babylonica, and the plate-root system of J. ailanthifolia is less efficient not with the same breast height diameter but with the same root volume. The average M_max of S. babylonica for overturning each species decreased linearly with increasing soil cohesion within the experimental range because root anchoring depth is restricted with increasing the soil cohesion.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.16.0_225
  DOI ID：10.11532/river.16.0_225, eISSN：2436-6714
• Report on Damage Situations by Tsunami Propagation in River Channels and its Overtopping from Embankment in Great East Japan Earthquake
  田中 規夫; 八木澤 順治; 安田 智史
  Volume：44, First page：21, Last page：24, 2010
  The tsunami caused by the Great Japan Earthquake at 14:46 JST on 11 March 2011, with a magnitude of 9.0 and epicenter 129 km east of Sendai, broke most of the sea embankment and coastal vegetation belt and caused catastrophic damage to people and buildings in the Tohoku and Kanto districts of Japan. A field survey was conducted to elucidate the damage situation of residential region by tsunami propagation in river channels and its overtopping from embankment. Abukumagawa River, Nanakita River and Old Kitakamigawa River located on Miyagi prefecture were selected for field investigation. In Abukumagawa River and Old Kitakamigawa River, overtopping flow from embankment occurred mainly at the outer-bank side of meandering section. Severe erosion was occurred on levee slope and neighboring houses were washed out by the scouring due to the overtopping flow. The hinterlands of coast and river had tsunami from two directions, coast and river, and the damage situation including the evacuation action for people became complex. Therefore, it is necessary to elucidate the location where tsunami is easy to be overtopped for different tsunami conditions.
  Japanese
  ISSN：1880-4446, CiNii Articles ID：120005386080
• Effects of tree characteristics and substrate condition on critical breaking moment of trees due to heavy flooding　　　　　　　　　　　　　　　
  Norio Tanaka; Junji Yagisawa
  LANDSCAPE AND ECOLOGICAL ENGINEERING, Volume：5, Number：1, First page：59, Last page：70, Feb. 2009
  To elucidate tree breakage conditions with different breaking mechanisms, i.e., moment by drag force, local scour, and degradation of the substrate around trees, field surveys were conducted after a flood event (September 2007 flood due to Typhoon 9) in the Tamagawa River, Japan. Trees in a river have two main breaking mechanisms during a flood event, moment by fluid force and erosion of the substrate. Moment by fluid force causes two breaking phenomena, trunk damage (bending, breakage) and overturning. Trunk bending or breakage can be expressed as a function of d (c) , where d is the trunk diameter at breast height and the power c equals 3 for trunk bending or breakage, and approximately 2 for overturning. Smaller diameter trees experienced trunk breakage, but larger trees were overturned. The range for these two breaking patterns changes with the substrate condition. If severe scouring has occurred, the threshold for overturning moment can be quite small. Tree overturning occurred mostly on the bank side of the gravel bar; however, some trees, especially Robinia pseudo acacia and Morus bombycis, were overturned if the substrate was a thin deposited soil or silt layer on gravel. The roots were anchored in the small-particle deposited layer in that case. As for the erosion of the substrate, the tree-breaking patterns can be classified into three types depending on the relationship between the nondimensionalized bed shear stress of d (50) and d (84), the representative grain diameters at which 50 and 84% of the volume of the material, respectively, is finer. The nondimensionalized shear stress of d (84) is an important parameter for discussing the rehabilitation of the gravel bed bar. The boundary region for tree overturning can be changed by the effects of plant cover and debris attachment.
  SPRINGER TOKYO, English
  DOI：https://doi.org/10.1007/s11355-008-0060-5
  DOI ID：10.1007/s11355-008-0060-5, ISSN：1860-1871, Web of Science ID：WOS:000263118100006
• 護床ブロックの洪水に対する安定条件に関する研究　　　　　　　　　　　　　　　
  井上浩一; 田中規夫; 八木澤順治
  Volume：53, First page：961, Last page：966, 2009
• 砂礫州上における繁茂場所の相違が樹木の洪水時流失限界に及ぼす影響　　　　　　　　　　　　　　　
  田中規夫; 八木澤順治
  Volume：53, First page：631, Last page：636, 2009
• 河道内植生の洪水による破壊・再生を考慮した植生動態モデルの開発　　　　　　　　　　　　　　　
  八木澤順治; 田中規夫
  Volume：53, First page：1171, Last page：1176, 2009
• 護床ブロックの洪水に対する安定条件に関する研究　　　　　　　　　　　　　　　
  井上浩一; 田中規夫; 八木澤順治
  水工学論文集, Volume：53, First page：961, Last page：966, 2009
• 砂礫州上における繁茂場所の相違が樹木の洪水時流失限界に及ぼす影響　　　　　　　　　　　　　　　
  田中規夫; 八木澤順治
  水工学論文集, Volume：53, First page：631, Last page：636, 2009
• 河道内植生の洪水による破壊・再生を考慮した植生動態モデルの開発　　　　　　　　　　　　　　　
  八木澤順治; 田中規夫
  水工学論文集, Volume：53, First page：1171, Last page：1176, 2009
• METHOD FOR CLASSIFYING THE POSSIBLITY OF FORESTATION IN A RIVER CONSIDERING THE DIFFERENCE OF BREAKING PATTERN OF TREES ON A GRAVEL-BED BAR　　　　　　　　　　　　　　　
  YAGISAWA Junji; TANAKA Norio; FUKUOKA Shoji
  Advances in River Engineering, Volume：15, First page：153, Last page：158, 2009
  For evaluating the difference of tree breaking phenomena due to floods, i.e. trunk breakage or overturning, and wash-out of trees, Breakage or Overturning Index(BOI)and Wash-Out Index (WOI) were derived respectively in this study. Based on these indices, the method for classifying the dynamics of forestation in rivers was proposed. This method was applied to the middle stream reach of the Arakawa River The situation of ’breaking’ or ’washing out’ on a gravel-bedbar after 2007 flood can be evaluated by using BOI and WOL In addition, in three locations where relative height from ordinary water level isdifferent, the relationships between flood return period and breaking mode of trees due to floods were demonstrated. At the location where relative height is the smallest, possibility of forestation should be low because wash-out of trees occurs by 5 to 10 years return period of floods. In contrast, possibility of forestation should be high at the location where relative heightis the biggest, because wash-out of trees doesn’t occur by 40 years return period of floods. This method is available to judge the area where artificial management of trees is required.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.15.0_153
  DOI ID：10.11532/river.15.0_153, eISSN：2436-6714
• 砂礫州上に繁茂する植生の洪水時流失限界評価　　　　　　　　　　　　　　　
  八木澤順治; 田中規夫; 福岡捷二
  Volume：14, First page：139, Last page：144, 2008
• 河道内樹木の洪水破壊形態と破壊限界値の基盤土壌条件による相違　　　　　　　　　　　　　　　
  田中規夫; 八木澤順治; 佐々木寧; 福岡捷二
  Volume：52, First page：649, Last page：654, 2008
  DOI：https://doi.org/10.2208/prohe.52.649
  DOI ID：10.2208/prohe.52.649
• 砂礫州上に繁茂する植生の洪水時流失限界評価　　　　　　　　　　　　　　　
  八木澤順治; 田中規夫; 福岡捷二
  河川技術論文集, Volume：14, First page：139, Last page：144, 2008
  Trees in rivers sometimes become driftwoods at flood events, and it might cause a disaster. It is important to understand the uprooting condition of the trees by floods. 2D unsteady depth-averaged flow model was applied to the Arakawa River between 76 km to 82 km for evaluating September 2007 flood and October 2006 flood. This model expressed well the peak water levels of the floods. Threshold drag moment and shear stresses for up-rooting the representative vegetation, Salix subfragilis and Robinia pseudoacacia, which grew on the gravel-bed bar in the upstream of the Kumagaya-Ohashi was evaluated according to the result of numerical analysis and the washed-out situation of the plants. Threshold drag moment for tree-uprooting on the gravel-bed was larger compared with the previous experimental results by pulling test. Flood discharge for which all plants on this gravel-bed bar were washed away was evaluated by comparing the calculated shear stress in each discharge condition and the threshold shear stress for uprooting obtained by the analysis.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.14.0_139
  DOI ID：10.11532/river.14.0_139, eISSN：2436-6714, CiNii Articles ID：10026287312
• 河道内樹木の洪水破壊形態と破壊限界値の基盤土壌条件による相違　　　　　　　　　　　　　　　
  田中規夫; 八木澤順治; 佐々木寧; 福岡捷二
  水工学論文集, Volume：52, First page：649, Last page：654, 2008
  For elucidating tree breakage condition with different breaking pattern, i. e. trunk breakage, tree overturn, local scour and degradation of the substrate of trees, and with different tree species, field investigation on tree damage situation after two flood events (October 2006 flood and September 2007 flood) were conducted in the Arakawa River and the Tamagawa River. Plant regeneration situation after 1year of the 2006 flood event was also conducted. If the breaking pattern is bending or partial breakage, the tree, Salix subfragilis, has a high productivity for regrowth. It implies that such breaking pattern is not so important if we consider the rehabilitation of gravel-bed river environment. The threshold moment of partial overturn of Robinia pseudo-acacia that has thin root zone was smaller compared with the previous experimental results by pulling trees because of a local scour. If severe scouring was occurred, threshold overturning moment can be quite small. The threshold moment can be found to be expressed as a function of the substrate condition.
  Japan Society of Civil Engineers
  DOI：https://doi.org/10.2208/prohe.52.649
  DOI ID：10.2208/prohe.52.649, ISSN：0916-7374, eISSN：1884-9172, CiNii Articles ID：130004044087
• Analyses on the threshold moment by drag and critical bed shear stress at floods for breaking trees on gravel bars　　　　　　　　　　　　　　　
  田中 規夫; 八木澤 順治
  Volume：42, First page：42, Last page：43, 2008
  This paper reports the research project in Arakawa River and Tamagawa River related to breaking condition of trees vegetated on gravel bars. Field surveys and laboratory experiments were conducted for elucidating the tree breaking condition due to the flood. The river flow analysis is also applied to the Arakawa River for evaluating the tree wash-out condition. The tree breaking and tree wash-out can be evaluated by drag moment acting on the tree trunk and the non-dimensionalized bed shear stress, respectively. The threshold drag moment and shear stress are discussed and the papers are introduced in this manuscript.
  Japanese
  DOI：https://doi.org/10.24561/00016427
  DOI ID：10.24561/00016427, CiNii Articles ID：120005386063
• CHANGE OF CRITICAL BREAKING MOMENT OF TREES IN A RIVER BY THE DIFFERENCE OF MAGNITUDE OF FLOOD DISTURBANCE AND TREE AGE　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; AOKI Shinya; FUKUOKA Shouji
  Advances in River Engineering, Volume：13, First page：177, Last page：182, 2007
  For elucidating tree breakage condition with different tree species and tree age, field investigation on tree height h_v, trunk diameter at breast height d_BH, and tree projected area in vertical section, of Salix subfragilis and Robinia pseudoacacia were conducted on three gravel-bed bars in midstream of the Arakawa River. After a flood on October 2006, h_v, d_BH and trace water depth were investigated for trees which were broken or bent down by the flood. Loading test was conducted for deriving critical breaking moment of the tree trunk. Critical breaking moment of the two tree species were expressed by the function of d_BH,³ The critical breaking moment of Robinia pseudoacacia is lower than that of Salix subfragilis when the diameter is the same. Drag and drag moment acting on trees were calculated with different tree age and magnitude of flood disturbance. Return period of floods (T₂) was compared with the maximum tree age (T₁) at which tree is broken under critical breaking moment. Comparing T₁ with T₂ has the possibility to become an effective method for evaluating whether the habitat in a river has a tendency to be a forest or not.
  Japan Society of Civil Engineers, Japanese
  DOI：https://doi.org/10.11532/river.13.0_177
  DOI ID：10.11532/river.13.0_177, eISSN：2436-6714
• Change of Threshold velocity for gravel movement by runner expansion and growth of Phragmites japonica on a gravel bar : modeling approach　　　　　　　　　　　　　　　
  Tanaka, N; Yagisawa, J; Ogawa, T
  Volume：25, Number：1, First page：1, Last page：10, 2007
• CHANGE OF THRESHOLD VELOCITY FOR GRAVEL MOVEMENT BY RUNNER EXPANSION AND GROWTH OF Phragmites japonica ON A GRAVEL BAR : MODELING APPROACH　　　　　　　　　　　　　　　
  TANAKA Norio; YAGISAWA Junji; OGAWA Tomohiro
  Doboku Gakkai Ronbunshuu B, Volume：51, Number：1, First page：1255, Last page：1260, 2007
  he effect of flood disturbance on the morphology of runners, plant productivity and runner-expansion characteristics of Pharagmites japonica was investigated at midstream of the Arakawa River. The dynamic growth model of P. japonica was developed considering the effect of disturbance, i. e., the difference of runner morphology and shoot productivity in the parent colony. The aboveground biomass distribution along the distance from the parent colony was well represented by the model. For analyzing the effect of flood disturbance interval, maximum water levels at three flood events were calculated and evaluated whether the habitat of P. japonica were inundated or not. In addition, the threshold friction velocity of the average grain diameter was compared with the friction velocity at the flood event. Although the gravel movement possibility has a little different tendency with the damaged situation of P. japonica, the clear relationship between the flood interval and the productivity in each habitat is found. The analysis indicates the possibility to calculate the plant productivity under the effect of flood disturbance.
  Japan Society of Civil Engineers, English
  DOI：https://doi.org/10.2208/prohe.51.1255
  DOI ID：10.2208/prohe.51.1255, ISSN：0912-2508, CiNii Articles ID：10021137809, CiNii Books ID：AA1045915X
• THRESHOLD OF GRAVEL MOVEMENT IN Eragrostis curvula VEGETATED ZONE AND ITS REMOVAL CONDITION BY FLOOD IN RELATION TO THE PLANT'S DENSITY AND GROWTH STAGE　　　　　　　　　　　　　　　
  YAGISAWA Junji; TANAKA Norio
  Doboku Gakkai Ronbunshuu B, Volume：51, First page：1249, Last page：1254, 2007
  Field observation was conducted to elucidate the effect of Eragrostis curvula on the threshold of gravel movement at midstream of the Arakawa River. Under various hydraulic conditions (particle diameter, bed slope and water depth) and growth conditions (colony diameter and density of the plant), Shields parameter of the gravel in the plant-vegetated area was estimated using the drag characteristics of the plant and calculated friction velocity affected by the plant. Threshold of gravel movement of median grain size (d₅₀) and d₈₄ (84% of the grain weight) around the plants was evaluated by comparing friction velocity of the flow condition with the critical friction velocity of the diameter. The removal threshold of Eragrostis curvula was defined at which the friction velocity affected by the plant's drag is equal to the critical friction velocity of d₈₄. The threshold condition related to HI (H: water depth, I: bed slope) and the drag by plant was validated for a flood in the Arakawa River and for two floods in the Yoshino River.
  Japan Society of Civil Engineers
  DOI：https://doi.org/10.2208/prohe.51.1249
  DOI ID：10.2208/prohe.51.1249, ISSN：0916-7374, eISSN：1884-9172, CiNii Articles ID：130003842392
• 河道内樹木の洪水撹乱規模と樹齢による破壊限界変化　　　　　　　　　　　　　　　
  田中規夫; 八木澤順治; 青木信哉; 福岡捷二
  河川技術論文集, Volume：13, First page：177, Last page：182, 2007
• Change of Threshold velocity for gravel movement by runner expansion and growth of Phragmites japonica on a gravel bar : modeling approach　　　　　　　　　　　　　　　
  Tanaka, N; Yagisawa, J; Ogawa, T
  J, of Hydroscience and Hydraulic Eng., Volume：25, Number：1, First page：1, Last page：10, 2007
• 洪水攪乱影響の違いがツルヨシの形態的特徴と繁茂量・拡大幅に与える影響　　　　　　　　　　　　　　　
  青木信哉; 田中規夫; 八木澤順治
  水工学論文集, Volume：51, First page：1255, Last page：1260, 2007
  he effect of flood disturbance on the morphology of runners, plant productivity and runner-expansion characteristics of Pharagmites japonica was investigated at midstream of the Arakawa River. The dynamic growth model of P. japonica was developed considering the effect of disturbance, i. e., the difference of runner morphology and shoot productivity in the parent colony. The aboveground biomass distribution along the distance from the parent colony was well represented by the model. For analyzing the effect of flood disturbance interval, maximum water levels at three flood events were calculated and evaluated whether the habitat of P. japonica were inundated or not. In addition, the threshold friction velocity of the average grain diameter was compared with the friction velocity at the flood event. Although the gravel movement possibility has a little different tendency with the damaged situation of P. japonica, the clear relationship between the flood interval and the productivity in each habitat is found. The analysis indicates the possibility to calculate the plant productivity under the effect of flood disturbance.
  Japan Society of Civil Engineers
  DOI：https://doi.org/10.2208/prohe.51.1255
  DOI ID：10.2208/prohe.51.1255, ISSN：0916-7374, eISSN：1884-9172, CiNii Articles ID：10021137809, CiNii Books ID：AA1045915X
• シナダレスズメガヤの繁茂量の違いを考慮した土砂移動限界の変化および洪水時流失条件の評価　　　　　　　　　　　　　　　
  八木澤順治; 田中規夫
  水工学論文集, Volume：51, First page：1249, Last page：1254, 2007
  Field observation was conducted to elucidate the effect of Eragrostis curvula on the threshold of gravel movement at midstream of the Arakawa River. Under various hydraulic conditions (particle diameter, bed slope and water depth) and growth conditions (colony diameter and density of the plant), Shields parameter of the gravel in the plant-vegetated area was estimated using the drag characteristics of the plant and calculated friction velocity affected by the plant. Threshold of gravel movement of median grain size (d₅₀) and d₈₄ (84% of the grain weight) around the plants was evaluated by comparing friction velocity of the flow condition with the critical friction velocity of the diameter. The removal threshold of Eragrostis curvula was defined at which the friction velocity affected by the plant's drag is equal to the critical friction velocity of d₈₄. The threshold condition related to HI (H: water depth, I: bed slope) and the drag by plant was validated for a flood in the Arakawa River and for two floods in the Yoshino River.
  Japan Society of Civil Engineers
  DOI：https://doi.org/10.2208/prohe.51.1249
  DOI ID：10.2208/prohe.51.1249, ISSN：0916-7374, CiNii Articles ID：130003842392
• Investigation on the damage by Indian Ocean Tsunami at the southern coast in SriLanka in relation to the breaking moment of the tree trunk in coastal vegetation　　　　　　　　　　　　　　　
  MOWJOOD M.I.M.; JINADASA K.B.S.N.
  Volume：39, First page：58, Last page：65, Jul. 2006
  This study explored the effects of coastal vegetation and sand dune on tsunami protection based on field observations carried out in two periods after the Indian Ocean tsunami. First one was conducted for elucidating the relationship between the representative species and the damage, from 1 to 6 April 2005 in Sri Lanka. The second survey was conducted for investigating the breaking condition of the representative trees, from 5 to 9 January, 2006 at Kalutra, Medilla, Rekawa and Hambantota where the combination of the sand dune followed by vegetation towards landside played an important role. The breaking moment of trees were investigated for the representative trees by pulling test. The threshold value for breaking condition was derived as a function of trunk diameter. The breaking moment equation represents well in the limitation of the representative species with the tsunami height at the tsunami event considering the aerial root height. These findings have to be considered in future coastal landscape planning and tsunami hazard mapping.
  Japanese
  DOI：https://doi.org/10.24561/00016113
  DOI ID：10.24561/00016113, ISSN：1880-4446, CiNii Articles ID：120001370425
• 砂礫河原に繁茂する株状草本シナダレスズメガヤの土砂捕捉特性と洪水攪乱による除去条件　　　　　　　　　　　　　　　
  田中規夫; 八木澤順治; 青木信哉
  Volume：12, First page：455, Last page：460, 2006
• ツルヨシのランナーによる群落拡大が土砂の移動限界に与える影響　　　　　　　　　　　　　　　
  八木澤順治; 田中規夫; 青木信哉
  Volume：50, First page：1177, Last page：1182, 2006
  DOI：https://doi.org/10.2208/prohe.50.1177
  DOI ID：10.2208/prohe.50.1177
• 砂礫河原に繁茂する株状草本シナダレスズメガヤの土砂捕捉特性と洪水攪乱による除去条件　　　　　　　　　　　　　　　
  田中規夫; 八木澤順治; 青木信哉
  河川技術論文集, Volume：12, First page：455, Last page：460, 2006
• ツルヨシのランナーによる群落拡大が土砂の移動限界に与える影響　　　　　　　　　　　　　　　
  八木澤順治; 田中規夫; 青木信哉
  水工学論文集, Volume：50, First page：1177, Last page：1182, 2006
  The effect of the enlargement of Phragmites japonica on the threshold of gravel movement was investigated by field observation at midstream of the Arakawa River. The lateral biomass distribution was simulated by the growth dynamic model of P. japonica including their shoot characteristics. The extended width by runner system was about 30 m, almost coincided with the width of the 3 year's plant stand in field. The effect of the plant enlargement on the threshold of gravel movement as evaluated by the lateral distribution of the drag force in relation to the plant biomass. The analysis indicated that the area lower than the threshold of gravel movement becomes exponentially large after 3-5 years with no disturbance even if the initial colonization is scattered.
  Japan Society of Civil Engineers
  DOI：https://doi.org/10.2208/prohe.50.1177
  DOI ID：10.2208/prohe.50.1177, ISSN：0916-7374, eISSN：1884-9172, CiNii Articles ID：130004043767
• 飛沫通過量を最小にする最適防風フェンス構造に関する風洞実験<論文>　　　　　　　　　　　　　　　
  田中 規夫; 高木 利光; 山崎 典和; 児玉 敏雄; 八木澤 順治
  Volume：39, First page：66, Last page：73, 2006
  type:text
  For decreasing the spray flux by wave-breaking at the shoreline to the landward area, the optimal wind protection fence structure was discussed. For minimizing the salt-spray flux through the fence, the structure with two low circular or L-shaped cylinders in staggered grid arrangement was selected and wind tunnel experiments were conducted with different spacing for cross-stream and stream-wise direction. The salt spray amount settling at the fence and passing through the fence were measured. The spray volume getting through or blowing up the fence was quantified by colored water with dye. The water was sprayed with a sprayer and collected by gauzes setting at downstream points. For the subsidence volume at the bottom in downstream, a tray was put and the mass of the subsiding water was measured. Considering the loss by blowing upward of the fence, the appropriate arrangement was found as `the two rows of circular cylinders with staggered, 1D cross-stream spacing and 1D-2D stream-wise length, where D is the diameter of a circular cylinder’. This amount of the subsidence is about 90% and more than the value of previous-existed fence structure, 70%.
  Japanese
  DOI：https://doi.org/10.24561/00016114
  DOI ID：10.24561/00016114, ISSN：1880-4446, CiNii Articles ID：120006387948
• Appropriate flood intensity to the wetland in old meandering river trace considering the regrowth process of emergent macrophytes　　　　　　　　　　　　　　　
  Das S.C.
  Volume：38, First page：58, Last page：65, Mar. 2005
  Field experiment was conducted for elucidating the damage effect on the productivity of wetland species, Phragmites australis, and upland species, Miscanthus sacchariflorus, in a river-floodplain. River flow was analyzed by two-dimensional depth-averaged Reynolds equation to solve the moment acting on the stems. Regrowth dynamic model considering their stem-breaking was formulated and their growth was analyzed in relation to flood discharge, flood interval and their stem-breaking moment. If their stem breaking is occurred every year, survival of the two species is difficult. However, they can survive with 2-5 years' interval and the superiority of M. sacchariflorus is decreased with stem-breaking condition. However, the breaking moment of M. sacchariflorus was larger than that of P. australis and the decrement in belowground biomass was smaller under bending damage. This indicates that the weak flood does not change their competitive superiority.
  Japanese
  DOI：https://doi.org/10.24561/00016079
  DOI ID：10.24561/00016079, ISSN：1880-4446, CiNii Articles ID：120001370748
• BELOWGROUND DYNAMICS AND STRATEGIES OF EMERGENT MACROPHYTES, Typha angustifolia AND Zizania latifolia, AFTER CUTTING THEIR AERIAL SHOOTS　　　　　　　　　　　　　　　
  WATANABE Tetsuhiro; TANAKA Norio; TAKEMURA Takeshi; YAGISAWA Junji; ASAEDA Takashi
  PROCEEDINGS OF HYDRAULIC ENGINEERING, Volume：48, First page：1603, Last page：1608, 2004
  Typha angustifolia were cut in June, July and August in 2002, and in May and July in 2003 for i nvestigating their strategy to survive from cutting at different timing. Zizania latifolia was also cut in July in 2003. The cutting effects were evaluated quantitatively by regrowth characteristics of aboveground leaves just after cutting. The belowground production of T. angustifolia was decreased by summer cutting. This was due to the decrement of transportation from original shoot to belowground and from regrowth shoot to belowground organ. July to August is the best season for controlling expansion of the species, because the transportation can be decreased by the cutting. The amount of transportation from belowground to aboveground organ was a little compared with the decrement of belowground biomass and was almost the same with the two species, but heterotrophic season just after cutting were found 15 days, 40days in case of T. angustifolia and Z. latifolia, respectively. The season was longer and secondary shoot was formed in case of Z. latifolia. This implies the different strategy of Z. latifolia with T. angustifolia.
  Japan Society of Civil Engineers
  DOI：https://doi.org/10.2208/prohe.48.1603
  DOI ID：10.2208/prohe.48.1603, ISSN：0916-7374, eISSN：1884-9172, CiNii Articles ID：130004043578

• 落葉層が降雨時の火山灰流出量に及ぼす影響に関する実験的研究　　　　　　　　　　　　　　　
  桑原哲也; 八木澤 順治
  Mar. 2025
  Mar. 2025 - Mar. 2025, Japanese, Oral presentation
• Flow structures and sedimentation characteristics around colony-type vegetation at flood events　　　　　　　　　　　　　　　
  2008
• Evaluation of removal condition of invasive plant ‘Eragrostis curvula’ by considering erosion rate　　　　　　　　　　　　　　　
  2008
• 株状粗度群内の底面せん断力特性の評価に関する実験的研究　　　　　　　　　　　　　　　
  2008
• 側岸侵食が樹木の流失限界に及ぼす影響　　　　　　　　　　　　　　　
  2008
• Differences of Tree-breaking Pattern and Breaking Moment by Floods with Different Tree Age and Substrate Condition under Two Flood Disturbances　　　　　　　　　　　　　　　
  2008
• Flow structures and sedimentation characteristics around colony-type vegetation at flood events　　　　　　　　　　　　　　　
  16th Congress of Asia and Pacific Division of International Association of Hydraulic Engineering and Research and 3rd IAHR International Symposium on Hydraulic Structures, 2008
• Evaluation of removal condition of invasive plant ‘Eragrostis curvula’ by considering erosion rate　　　　　　　　　　　　　　　
  ICHE(The 8th International Conference on Hydro-Science and engineering), 2008
• 株状粗度群内の底面せん断力特性の評価に関する実験的研究　　　　　　　　　　　　　　　
  土木学会第63回年次講演会, 2008
• 側岸侵食が樹木の流失限界に及ぼす影響　　　　　　　　　　　　　　　
  土木学会第63回年次講演会, 2008
• Differences of Tree-breaking Pattern and Breaking Moment by Floods with Different Tree Age and Substrate Condition under Two Flood Disturbances　　　　　　　　　　　　　　　
  ICHE, 2008
• 樹木群模型周辺の流れ構造と繁茂状態の異なる実樹木群周辺の土砂堆積特性　　　　　　　　　　　　　　　
  2007
• 河道内樹木の鉛直構造の違いを考慮した合成抗力作用高さの変化　　　　　　　　　　　　　　　
  2007
• 樹木群模型周辺の流れ構造と繁茂状態の異なる実樹木群周辺の土砂堆積特性　　　　　　　　　　　　　　　
  土木学会第62回年次講演会, 2007
• 河道内樹木の鉛直構造の違いを考慮した合成抗力作用高さの変化　　　　　　　　　　　　　　　
  土木学会第62回年次講演会, 2007
• シナダレスズメガヤ周辺の土砂移動限界の変化および同植物の洪水時除去条件　　　　　　　　　　　　　　　
  2006
• Plant expansion modeling for analyzing the change of the threshold velocity of gravel movement　　　　　　　　　　　　　　　
  2006
• Effects of flood interval on the growth of Phragmites japonica and the change of threshold velocity for gravel movement　　　　　　　　　　　　　　　
  2006
• シナダレスズメガヤ周辺の土砂移動限界の変化および同植物の洪水時除去条件　　　　　　　　　　　　　　　
  応用生態工学研究会第10回大会, 2006
• Plant expansion modeling for analyzing the change of the threshold velocity of gravel movement　　　　　　　　　　　　　　　
  ICEM2006, 2006
• Effects of flood interval on the growth of Phragmites japonica and the change of threshold velocity for gravel movement　　　　　　　　　　　　　　　
  15th APD-IAHR Congress, 2006
• 洪水攪乱により土砂被りを受けたツルヨシの翌年の再生長特性　　　　　　　　　　　　　　　
  2005
• 礫河原における多年生草本シナダレスズメガヤ(Eragrostis curvula)の除去条件の評価　　　　　　　　　　　　　　　
  2005
• 洪水攪乱により土砂被りを受けたツルヨシの翌年の再生長特性　　　　　　　　　　　　　　　
  応用生態工学研究会第9回大会, 2005
• 礫河原における多年生草本シナダレスズメガヤ(Eragrostis curvula)の除去条件の評価　　　　　　　　　　　　　　　
  応用生態工学研究会第9回大会, 2005

• 2024
• 2024

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  Competitive research funding
• -　　　　　　　　　　　　　　　
  Competitive research funding