河川高灘地使用之研究

Abstract

近年來因為社會繁榮及經濟之成長，使民眾生活水準提高，相對也要求環境品質之提昇，在土地狹窄且價格高昂之情況下，遂有利用河川高灘地供綠美化及休閒遊憩設施之構想；然而水利法第七十八條之規定，河川行水區內不得有妨礙水流之行為，因此河川高灘地之利用受阻。 本文針對在維護河防安全之原則下，以河川餘裕之出水高空間供河川高灘地使用所產生之水位壅高，本文定義河川安全出水高在平直河段為V2/2g，在平緩彎曲河段為 1.66V2/2g，並依既有之出水高訂定允許高灘地使用之水流速度，本文亦依高灘地允許使用之程度，按喬木植栽，灌木植栽及遊憩設施等，提供允許使用密度，及其使用後粗糙係數之計算方法，供高灘地使用規劃時之參考，以求紓解高灘地使用之壓力及行水區內不得有妨礙水流行為間之癥結，期使河防安全與環境品質提昇並存。

The recent economic developments has improved living standards of residents in Taiwan, and therefore a better environmental quality has to be promoted accordingly. Due to limited land sources and high land costs in Taiwan, the utilization of flood plain as recreational area is urgently needed. However the utilization of flood plain is often limited by law that any activities causing flow retardation are prohibited. This article recommends to use the excessive free board for the increase of water surface elevation caused by flood plain utilization under the condition that flood safety shall be maintained. A safe free board is defined in this article as V2/2g for straight reaches and 1.66V2/2g for reaches with gradual bend, and allowable flow velocities are suggested for flood plain utilization based on existing free boards. This article further provides methods of calculating allowable density for planting and recreational facilities as well as calculating roughness coefficients after flood plain utilization. The study results could be used as a tool for planning of flood plain utilization. Hopefully, the conflict between flood plain utilization and the limitation of flow retardation could be resolved.