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河川作物種植規範之研議
On Regulations of Floodplain Vegetations
摘要
近年來本省河川高灘地已逐漸開發作爲河濱公園從事農業生產，若恣意地開發而不加以規範，由於過多的人工結構物及植栽的存在，將使原有河槽的通水能力降低，使得原有的防洪構造無法提供原設計的安全度，危及堤內人民生命財產的安全。由於本省目前尚無完善的河灘管制法規，使得欲加以管制却於法無據，農業及水利單位對此問題十分重視，故委託臺大水工所進行研究，訂定合理的高灘地植栽規範，以對於高灘地的開發加以管制，達到安全而有效的土地利用。本研究以日本目前試行之高灘地植栽法規爲參考、河川作物種植規範之研議（第一期）報告爲基礎，將植栽作物按高度分成高木作物（一公尺以上）、矮樹（五十公分至一公尺）及低木作物（五十公分以下），以水平二維水理模式（TABS-2）進行模擬，進而訂定合理之種植規範。依照模擬之結果，本研究認爲：一、高木作物宜採取單植，不宜叢植；各木間相互獨立縱距爲一百倍等值樹幹直徑。二、矮樹植栽範圍須距堤脚與低水河槽肩部十公尺以上；間隔須在五十公尺以上；植栽後之最大水位抬升率不得大於百分之十二；植栽作物之曼寧n值由MEI公式定之。三、低莖作物植栽範圍須距堤脚與低水河槽肩部十公尺以上；間隔須在五十公尺以上；植栽後之最大水位抬升率不得大於百分之十二；植栽作物之曼寧n值由MEI公式與周文德之表定之。
並列摘要
Due to over inhabitation, some of the floodplains are developed for recreational or agricultural application. To set up a regulation to regulate the floodplain activity is an urgent task in Taiwan. The purpose of this study is to set up a regulation according to our numerical simulation. A horizontal 2-D model developed by U.S. Army Corps, TABS-2, is adopted in this study and the Japanese regulations on floodplain vegetations is our major reference. The important findings are listed as follows: 1. The floodplain vegetations can be classified into three categories, namely high tree, low tree and bushes, according to their heights. The high trees are those vegetations taller than 1 m, the low trees are those between 1 m and 0.5 m and the rest are bushes. 2. The high tree has to be planted individually, and the minimum longitudinal distance between two adjacent trees has to be 100 equivalent diameters. 3. The minimum distances between the low trees and the footings of the dikes and the edge of the low flow channel have to be 10 m and the lateral distance between two adjacent rows has to be 50 m. The maximum allowable increment of the water surface elevation is set to be 12%. The corresponding Manning's coefficients are determined using MEI equation. 4. The regulations for the boushes are same as those of the low trees.