This study aims to evaluate the applicability of satellite imagery in estimating the percentage of impervious area in urbanized areas. Two methods of estimation are proposed and applied to a small urbanized watershed in Japan. The area is considered under two different cases of subdivision; i.e., 14 zones and 17 zones. The satellite imageries of LANDSAT-MSS (Multi-Spectral Scanner) in 1984, MOS-MESSR(Multi-spectral Electronic Self-Scanning Radiometer) in 1988 and SPOT-HRV(High Resolution Visible) in 1988 are classified. The percentage of imperviousness in 17 zones is estimated by using these classification results. These values are compared with the ones obtained from the aerial photographs. The percent imperviousness derived from the imagery agrees well with those derived from aerial photographs. The estimation errors evaluated are less than 10%, the same as those obtained from aerial photographs.

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In this paper, a model for simulating the development of flood flow in a river network is introduced and then is applied for a real network.

The runoff discharge model developed for an urbanized watershed is extensively applied to examine the usefulness of the rainwater infiltration facilities to control the water level during flooding . The rainwater infiltration facilities examined are the permeable pavement and the house infiltration system . From the simulated results the followings are clarified . Reinforcement of permeability covering the pervious ground surface with the permeable pavement is ineffective to lower the water level. The peak water level is reduced by replacing the impermeable pavement with the permeable one in the parking lots . And multiple use of the rainwater infiltration facilities is effective for decreasing the occurrence of inundation by lowering the water level and is effective to delay the time of peak water level .

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