Osamu Hinokidani

Effects of the Check Dam System on Water Redistribution in the Chinese Loess Plateau

AbstractThe objectives of this study are to evaluate the effects of the check dam system on water redistribution in a small basin in Chinese Loess Plateau by using a practical numerical method for the water budget process. Hydrological and meteorological observations were carried out in the small dam basin (0.43  km2). To quantitatively evaluate the effects of the check dam system on the water redistribution, hydrogeological modeling was applied to the check dam system in the basin. The numerical modeling was developed by kinematic wave theory for water flow. The model was verified by the numerical simulation of surface runoff discharge and groundwater level. Numerical calculation was carried out on the water budget of two cases: Case 1, no check dam (the control), and Case 2, with the check dam system in the year 2006. The model showed that the water budget of the surface runoff and groundwater flow in Case 1 was 97.3 and 2.7%, respectively. Conversely, the water budget of the runoff, evapotranspiration,...

Structural Universality of the Distributed Hydrological Model for Small- and Medium-Scale Basins with Different Topographies

AbstractDeveloping a distributed hydrological model that is applicable to a variety of topographies is a substantial challenge to the hydrological modeler. The primary objective of this study was t...

RUN-OFF ANALYSIS METHOD OF SURFACE-SUBSURFACE WATER FLOW USING TRIANGLE SCHEME

Two-dimensional runoff analysis with rect-linear finite differential scheme or one-dimensional runoff analysis with more complex finite differential scheme has been studied. We propose triangle scheme that covers ground surface to make a numerical model of the ground surface topography and strata structure. The ground surface is covered by point-polygon system and the vertexes of a polygon are defined at the gravity centers of triangles surrounding the point. The topography and strata structure are explained by the elevation of ground surface and boundary of each stratum. The depth is defined at the point and the flux is defined at the gravity center of the triangle. Based on the arrangement of variables, two-dimensional runoff analysis can be done. We apply kinematic wave theory to the triangle scheme and show an example of calculation.

The Support Functions for Cooperation in the River Basin through Structural Analysis of the Problems

近年、健全な水循環系の回復や地域活性化の必要性等 から、市民、行政、企業、専門家等の流域連携による環 境保全や地域振興が各地で盛んになっている。先の全国 総合開発計画 「21世 紀の国土のグランドデザイン」1) でも、第三次全国総合開発計画で提唱された 「流域圏」 という圏域を、国土保全 ・管理の基本的単位として位置 づけ直し〔1〕 、多様な主体の参加と連携による取組みを推 進することが示されている。しかし、このような取組み には問題、課題点も多く、よりよい取組みの方途が官民 双方から求められている。 流域連携に関する研究としては、流域の特徴や流程の 変化と住民の意識・行動の関連性を分析したもの2)3)や 、 上下流住民の意識から連携の可能性を探ったもの4)、多 様な主体が連携するための仕組みづくりを提案したもの 5)等があるが 、まだまだ研究の数が少ない。このような 中、本研究に先駆け著者らは、全国各地で取組まれてい る水環境保全活動の実態と傾向を明らかした上で、市民 活動と、行政、企業、専門家等の役割連携のあり方につ いて分析・考察を行った6)。 一方、最近、旧国土庁計画・調整局は(財)リバーフロン ト整備センターに委託し、全国の先進的な流域連携の事 例調査を行 う他、各流域のキーパーソンの参加を求め計 2回 の懇談会を開催するとともに、関連分野の学識・有識 者にヒアリングを行い、流域圏を単位とした取組みの意 義や効果、課題点等について意見を聴取した7)。本研究 は、この調査から得 られた意見の整理 ・分析を通 して、 流域連携の有効性、課題点を確認するとともに、流域連 携を支援する方策について明らかにする。

Characteristics of Bed Variation at River Contraction during Flood

The characteristics of river bed variation at the contraction during the flood are investigated exprimentally. Moreover its characteristics for natural river which have several types of contraction are investigated by the numerical simulation on the basis of one dimensional bed variation method. From the experimental results, it is found the tendency that the bed level approaches to the bed level on equilibrium condition of sediment discharge for flood discharge. As the results, the bed level lowers during rising stage and then phenomenon of bed aggradation during the falling stage occurs at the up-stream end of the contraction. It is found from the numerical simulations that the bed variation of the contraction is influenced by the approach length, length of contraction and duration of the flood.