Representation of Numerical Basin Model in the Rural and Mountainous Region by Image Processing and Its Application to Forecasting of Flood Runoff

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The study purposes to provide an application of topographic information in watershed to the forecast of runoff through the computer workstation. Especially, a discussion is developed on setting the viewpoint at moutainous rural area in San-in district. The results are as follows : 1.(1) Modified runoff models based on the long and short term runoff model or the lumped KiWS model were proposed for the analysis considering the effect of basin topography and distribution of impermeable area. (2) Runoff calculation system was constructed, by using UNIX workstation, to cany out a series of analysis including data input ; runoff analysis ; and output of hydrographs. 2. (1) The behavior of hydrological water balance and mass balance of pollutant were mesured in a paddy field watershed, where a circular irrigation system is implemented. The contribution of the water drawn from extra area and circulation, the mass balance of pollutants and sediment to the improvement of river basin environment was considered. (2) The hydrological properties were evaluated in the experimental lysimeters. As a result, the amount of percolation water amounted for 60% of precipitation and the surface runoff occurred after the cumulated precipitation reached a certain degree. 3. (1) Soft X-ray radiography of water flow in undisturbed paddy soils, upland field soils and forest soils were carried out. Vertical, independent root channels in paddy soils and networked root channels in upland fields conduct the water flow, On the other hand, interaggregate macropore flow has been observed in forest soils. Resultant Reynolds number for paddy field and upland field soils showed 50-80, which indicated macropore flow was in a transition region from laminar to turbulent.