A MEASURE OF ESTIMATING THE RELATION BETWEEN THE CHANGE OF RUN-OFF BY URBANIZATION AND URBANIZED BASIN

Abstract

The flood run-off form of medium and small rivers have been changing markedly with the improvement and expansion of public facilities such sewerage systems and roads. This paper describes the Urbanization Number, one of the urbanization indices which evaluate the relation between the progress of urbanization in the river basins in built-up areas and the change in the flood run-off form. The Urbanization Number is expressed by a linear model composed of percent impervious area, percent river improvement, percent sewerage improvement, etc. It is characterized in that it can quantify the degree of influence of the improvement of sewerage systems and rivers on the flood run-off form.
Moreover, the use of this Urbanization Number permits to easily estimate the run-off coefficient and effective rainfall in the national formula relating to the run-off characteristic of medium and small rivers in urban areas.