Yosihisa Ando

Recent Flood Control Measures for Urban Rivers in Japan: Case Study of the Kanda River in Tokyo

ABSTRACT Recently, floods occurred frequently almost everywhere in urban areas in Japan. These urban disasters became an important social problem. In the present study, we investigated floods on the Kanda River in Tokyo. The history of flooded areas, and flood control projects in progress, involving river improvements, expansion of sewerage projects, and urbanization, are reviewed. We also have presented our recent survey results for the flood of August 27, 1993 that occurred in the Kanda River Basin. Hydraulic and hydrologic impacts of historical floods are also given, including an investigation of the economic and social impacts. In urban areas, it is difficult to increase the width of the river. Thus, river improvement works essentially consist of the use of underground diversion channels. In Tokyo, Takadanobaba, Edogawabashi, and Suidobashi diversion channels have been completed. Regulating reservoirs along these rivercourses have been constructed in the Myoshoji River Basin and Zenpukuji River Basin....

Simulation of Conservation of a Spring in Groundwater Recharge by Rainwater

In this study, the conservation of a spring in groundwater recharge by rainwater is investigated using a hydrological model which includes the direct runoff, infiltration, evapotranspiration, groundwater recharge, and groundwater runoff for simulating the total runoff from the rainfall. The Kokubunji basin is chosen the study area. In the basin, the direct runoff from impervious areas discharges to one main stream, and the groundwater runoff originates from the unconfined aquifer. We assume that the groundwater runoff rate is proportional to the second power of the amount of stored groundwater, and the groundwater recharge is proportional to the soil moisture excess. The total runoff is simply obtained from the sum of the direct runoff and the groundwater runoff. The groundwater recharge in the Kokubunji basin is restricted because of permeable inlets through which the rainwater from roofs penetrates into the soil. Hydrological data from a rain gauge and a stream flow gauge in the area are used for analyses of the rainfall-runoff relationship. Computations were carried out by using the 1995’s hydrological data for 1000, 2000, 3000, and 4424 permeable inlets. The effects of the conservation of the spring in groundwater recharge by rainwater increase 26%, 52%, 78%, and 116% to the total runoff for 1000, 2000, 3000, and 4424 permeable inlets, respectively. The hydrological model has good applicability when calculated at intervals of one hour.

Development of a Distributed Hydrologic Model Using SMPT Model and its Application to the Azuma Upperriver Experimental Basin

The objective of this study is to improve a distributed hydrologic model using SMPT (Soil Moisture Parameter Tank) model by applying kinematic wave model to river flow routing changing time step of day to an hour. The watershed basin is divided into a grid cell of 50m. This model is composed of three structure; surfaces division, river division, and groundwater division. In surface division, evapotranspiration, infiltration, percolation, interflow, and surface outflow were computed in each cell. Kinematic wave model was applied to river flow components. Groundwater component computes the groundwater levels and the flows in the saturated zone of an unconfined aquifer, stream interactions, and groundwater seepage at the ground water surface. The model is applied to simulate water cycle in the Azuma Upper Experimental basin (1.81km2) with a time step of an hour. The model parameter is calibrated through comparison of the simulated river discharge, groundwater levels with the observed value.

ANALYSIS OF HYDROLOGICAL CYCLE IN THE AZUMA UPRIVER EXPERIMENTAL BASIN

Consciousness of the environment has raised in recent years. Many municipality corporations began conserving and reviving the ecological river front in urban areas which was deteriorated by urbanization. The first procedure for the river front conservation is to increase the ordinary water discharge of urban minor rivers, and the basic study for that is to clarify the hydrological cycle of such river basins.The present paper analyses the hydrological cycle in terms of groundwater runoff, direct runoff and groundwater storage in the Azuma upriver basin during 76 days in 1996, using the daily hydrological model for an urban basin which was presented by Ando et. al.(1982). The simulation resulted in approximation to the observed runoff hydrograph and the groundwater storage which was derived from the measured groundwater level. This paper also predicts the runoff hydrograph in the same period using the same model on the supposition that houses infiltration facilities are set in this basin. This simulation demonstrated that the groundwater runoff was increased and the direct runoff was reduced, that effect on restoring the ordinary water discharge.

Analysis of Hydrological Cycle of Spring in the Musasino Upland and Its Management

Hydrological cycle of the Kokubunji experimental basin in the Musasino upland was studied at the spring in the Kokubunji-manyo garden in relation to the applicability of the hourly concentrated hydrological model and the basin management by means of the houses infiltration facilities. The hydrological model can also be considered the surface infiltration capacity of the pervious area. The analyses were carried out for two years hydrological data in 1992 and 1993, in which the sewer system had been expanded and the inverting wells became scarcely used.The results indicated that the model generally reproduced observed runoff hydrographs, and the model applicability was confirmed. We also predicted the simulated hydrographs of which the assumption that the houses infiltration facilities were introduced, using the above hydrological model. It is found that the houses infiltration facilities are important for managing a basin in respect of the springs conservation.

Stormwat Reurn of Afn alysifs or the Urban Experimteanl Basin in Upland

In recent years, more spatial and temporal rainfall data are presented by progress of climatic observation technology, while the rapid human activities for basins like urbanization caused flooding problems.This paper describes the analysis of stormwater runoff model for the Yabata experimental basin (5.42km2) in urbanized Toshima Upland in Tokyo. And it was considered distributed rainfall data of 5 minutely from 6 autographic raingauges and distinguished infiltration capacity for land use.

Hydro-statistic Consideration on Efficiency of Infiltration Facilities at Houses

The authors introduce a fractional function for adaptation of a hystogram of hourly rainfall data for 13 years at Musashikoganei. Then, using the above fractional function, they develop relationship between infiltration capacity of infiltration facilities and ratio of infiltration to annual rainfall. And an example of estimation of efficiency of infiltration facilities at houses is shown for Kokubunji experimental basin.

Hydrological-environmental Considertion on Springs in Upper Region of Noh River

The authors make a field study on hydrological-environmental aspects on springs in upper region of Noh river. Water quantity and quality of 8 springs and Noh river had been observed once a month for 6 months (Aug., 1987-Jan., 1988). At first, it is made clear that the discharge of Noh river mainly consists of the discharges of the above springs. Discharges of several springs have a high correlation and linear regression analysis is done. And it is made clear that the discharges of 3 major springs consist of about 80% of Noh rivers discharge. It is also shown that correlation between electric conductivity and concentration of Cl is high and that regression line of those matters is obtained.