Evaluation of Effects of Stormwater Storage/Infiltration Facilities on Improvement of Urban Hydrologic System

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On-side storage/infiltration facilities have been introduced in many urbanizing river catchments in recent ten years as an effective measure for the improvement of urban hydrologic cycle such as flood runoff reduction, soil moisture supply, groundwater recharge etc..The main objective of this study is to develop not lumped type hydrologic model but physically-based distributed model capable of treating local characteristics as well as their change within the river catchment, in order to evaluate quantitatives effects of those on-site facilities.The major research results are summarized as follows ;(1) Since 1991, automatical observation of hydro-meteorological items including precipitation, water stage in stream, groundwater level, soil moisture, air temperature, humidity, net radiation, wind speed and direction, has been carried out in the Ebi river basin located in Funabashi City, Chiba Prefecture. In addition, artificial hydrologic componemts such as municipal water use, sewage infl … More ow, pumping-up of groundwater, irrigation for paddy fields etc.have been surveyed and estimated, based on related statistics published by located governments and hearing from related agencies.(2) Based on above observed and investigated data, a frame work of the hydrologic system in the Ebi river basin including both natural and artificial components was quantitatively clarified in each hydrologic year.(3) Observed hydrograph shows a very clear diurnal cycledue to the inflow from domestic sewage. The observed discharge was separated into natural and artificial components, using the above observed diurnal pattern and water supply data obtained from related agencies.(4) Data-base related to basin characteristics including land cover, soil hydraulic properties, population, water supply amount were arranged in the form of GIS,by using the software 'ARC/INFO'.(5) A3-dimensional distributed hydrologic model, including natural component sub-model, artificial component sub-model and storage/infiltration facilities sub-model, was constructed in one grid size of 50m^*50m based on the GIS data-base. After tuning model parameters and examining the validation of the model, effects for several cases of basin management were quantitatively evaluated through the simulation using the model. Less