Tadaoki Itakura

RUN-OFF MODEL OF WASH LOAD USING RIVER CHANNEL NETWORK

The run-off of the rain fall is very complex because it has various characteristics especially at the mountainous basin. If a run-off phenomenon can be reproduced well, the prediction of the sediment movement and so on become possible and effective to control and maintain the river channels.In this study, authors have developed the prediction model in which wash load was evaluated by using the channel network of the digital national land information and the kinematic wave model. The model can evaluate the flow rate and the sediment transport rate at any station in the river basin. The geographic and geological informations were obtained from the Ishikari River Area LandscapeIntelligences. It was applied to the Jouzankei Dam basin and compared with the field observations.

ESTIMATION OF SEDIMENT YIELD IN THE TAKISATO DAMBASIN

Authors proposed the network-moder for arguing a stable longitudinal profile on the basin. This model enables us to evaluate the longitudinal variations of dischare and sediment discharge, bed elevation, mean diameter of bed materials, width of channels and flow depth. In this model, there are some assumptions that discharge from the outer link in all the basin, sediment discharge from the outer link, inflow and sediment inflow from the side basin in the basin of branches are the same. In the real basin, those factors are complicated by geographical and geological configuration. So in this paper, those factors ate varied every unit river channel. The irnpnwed network-model is applied to the Takisato Dam basin. So, the sediment discharge at Takisato Dam is estimated. The animal volume of deposition could estimate extending conception of sediment discharge under dominant flow discharge. Estimated annual volume of deposition at sabo dams in the basin was verified with the value offield data.

ESTIMATION OF WIDTH OF RIVER CHANNEL AND MEAN DIAMETER BY THE NETWORK MODEL

Authors have analyzed the stable longitudinal distributions of river channels using the Network Model. It is very important for solving the problems, not only for river engineering but also for coastal or sabo engineering, dealing with sediment discharge to estimate annual characteristics of sediment yieldof rivers.In this study, we estimate the longitudinal distributions of the mean diameter and the width of river channels in Ashibetsu, Kanayama and Houheikyou Dam basins. Then the results are analyzed by field data.

A STUDY ON QUANTITATIVE EVALUATION OF RIVER LANDSCAPES

In recent years, various landscapes design and evaluation of landscapes in river space have been tried. But, they depend on intuition and feeling generally, and they are not quantitative. Therefore, the Analytic Hierarchy Process (AHP) is noted settling the problem. AHP is conceived by T. L. Saaty for trying to find the greatest common measure to make a judgment. AHP obeys the following, constructing hierarchy, making a pairwise comparison, deciding weight, calculating the consistency index, deciding synthetic weight.This study singled quantitative evaluation of river landscapes using AHP. It was concluded that this method is very useful.