不浸透面積率を考慮した長短期流出両用モデルによる流出解析

This report describes the application of the long and short terms runoff model（LST-II), which is developed by Kadoya and Nagai（1988）for analyzing both flood and long term runoff successively, to consider the effects of the land use form in the runoff process. The three type models are considered to introduce the the effects of non-uniformmity in the infiltration phenomina at top layer zone of slope system. The first attempt is discussed by runoff model I,II, in which infiltration capasity at the ground surface is limitted to a constant value or a same form of Horton curve induced by the change of subsurface condition. The third type of the modified LST-II model, runoff model III, is proposed to express the effects of distribution of permeable area and impermeable one in the basin. The impermeable area is developed by urbanization in a residental district and integrated rural improvement. In the runoff model III, the upper zone of first tank is divided two parts by the ratio of permeable area and impermeable one in the basin. The left part expresses the impermeabl field to occure surface runnoff easily. And the right one assigns the permeable field to arise both of surface runnoff and subsurface one.
These three runoff model is adapted to the experimental basin at land reclamation area in Masuda City. The runoff model I, II results almostly the same reproducibility of the observed hydrograph comparing the LST-II model. While, it is shown that the analysis by runoff model III improves the reproducibility of the peak discharge in observed hydrograph about 9％ than the LST-II model.

　自然丘陵山地の部分開発域あるいはスプロール的に混住化社会が進展する農村地帯等を含む地域を対象に流出特性を検討する際，その流域の地形・土地利用形態に応じた分布型の流域モデルを設定し，雨水流モデルに代表される，いわゆる分布定数型流出モデルによる解析が望まれる．一方，菅原タンクモデル，貯留関数法，長短期流出両用モデル等の貯留型流出モデルは，斜面流，河道流を区別することなく流出過程を極端に集中化したモデルであるから，雨水流モデルならば説明できるはずのいくつかの現象が説明できなくなる欠点を持っているといえる．したがって，自然丘陵山地の部分開発域等を含む流域に貯留型流出モデルを適用する際，流域の都市化現象と類似のいくつかの地文条件及び水文条件の変化をどのように流出モデルに組入れるかが課題となる．
本報告では，開発地域にみられるような舗装道路面積や水路網の具備の効果，あるいは地表条件の面積的な分布の効果を貯留型流出モデルによる流出解析に取入れることを目的に、長短期流出両用モデルを活用した手法でこうした課題への試みを意図して行った若干の検討例について述べる．