都市洪水診断カルテ

概要

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A new runoff analysis method based on Normal Basin Hydro-cycle Rate (NBHR model) was introduced in the previous paper1). Runoff Q2 at the basin outlet (elevation T2) consists of the inflow Q1 at the basin inlet (elevation T1), the direct flow from effective rain Qre=R(rainfall)－e(evapotranspiration) , the base flow Qbf＝T2×Sy determined by NBHR, and the indirect flow from the storage water Qst＝Qw ,as shown by Eq.(4) in the present paper. Each hydroterm is divided by its elevation,T1 ,T2 ,Tm, respectively, to maintain NBRH Sy. The analytical results of the daily, hourly, 10 minutely time base show that they are given by T1=T2=log(2), and Tm={log(10000)+log(2)}/2,in m. We can express the flood critical circumstance by Eq.(6),where R,S and Q1,Q2,Qw reach to the saturated Rc,Sy, and Q1*,Q2*,Qw*, respectively, and e, g (infiltration) are small and neglegible as compared with other terms. When we have much more R and Q1 in critical state, Q2 can be expressed as Eq.(8), in addition, river flood O as Eq.(9), and inundation I as Eq.(10). Thus we can simply make up flood diagnosis under the present channel conveyance capacity Q1*, Q2* with the heavy rain R. A diagnosis Karte is formed in the format as Table 1. It tells us how much rain the present Q1* and Q2* hold up, and offers a prescription on new Q1*, Q2*, against the ranked-up heavy rain.
山口大学工学部の論文