利用物理棲地模式檢討河川斷面的棲地適合度

Study on the Habitat Suitability of River Cross Section via Physical Habitat Simulation Model

許嘉文(Jia-Wen Syu)

指導教授 ： 詹明勇

義守大學/理工學院/土木與生態工程學系/碩士(2016年)

摘要

河川在自然環境中為一個具代表性的生態體系，過去多年以來因為氣候變遷或是雨量不均的影響，傳統的河川治理往往以供水或防洪為主要考量，而在上游設置許多橫向構造的攔河堰，滿足農工業、生活的用水量唯一操作依據，不過卻忽略了水域周邊中生物生存的環境需求。棲地的分布會因為河川中不同的水深、流速和其他不同底質等造成很多的變化。
自2000年開始，生態工程與河川生態保育意識也漸增，對於河川環境生物和基本生存權利，已成為水利工程在規劃設計中的一個重要考量，生態基流量一詞就在此時提出，並用於河川工程設計的準則裡。美國地質調查所於1980年開始對於保護指標魚類進行調查其適合生存環境，逐漸演變成所謂的適合度曲線與河川加權可使用斷面積(weighted usable area, WUA)的關係，來找出適合保護指標魚類該有的基流量。
本文以旗山溪之河段為研究案例，取其中較為關鍵的四個斷面(炳橋下至甲仙大橋下)這河段，利用物理棲地模式PHABSIM去演算相關生態棲息因子進行棲地之適合度曲線，在改變河川斷面積的概念下，結合特生中心裡的褐鱒魚與紅鱒魚作為初步魚種，以杉林溪大橋站的日平均流量(30cms)為基礎流量，檢討棲地與流量的影響，流量逐增加到60cms(四種情境)去找出可能用於水開發與維持生態基流量的折衷方案。研究顯示，高流量的情況下WUA會漸次增加，但較適合之水域仍在兩岸居多。若在各斷面設置橫向的固床工，則在低流量時WUA有減少的趨勢，當流量較大時WUA不受到影響，而且適生範圍也有較大的傾向。

關鍵字

生態基流量 ； 物理棲地模式 ； 適合度曲線

並列摘要

Due to the effect of climate change and uneven rainfall, main issues of river management focused on the flood control and water resources distribution. There are some weirs or dams built across the river bank without any consideration on the aqua-habitat properties that affected by various factors, such as velocity, depth or river bed materials.
Ecological engineering and river ecology conservation became the hot study topics since 2000. In order to meet the requirement of aqua-habitat, “base flow” or “ecological base flow” is proposed as the guidelines during river management or water resources planning. One of the distinguished studies on river habitat conservation or restoration, weighted usable area (WUA) concept, was initiated by USGS. WUA considers the combination of velocity, depth, bed-materials and water temperature to simulate suitable area for the specific aqua-species in stream.
Case study used in this paper is the reaches along Qishan River. Section properties (sectional profile, velocity, and discharge) from Bin-chiao to Chia-sian-chiao were collected. The suitable curve of red-trout and rainbow-trout were obtained from previous research report of Qishan River. Physical Habitat Simulation model (PHABSIM) developed by USGS is used in this paper to calculate the WUA under different flow rate and modification of cross section by groundsill works.
Discharges from 30cms to 60cms are assumed as flow conditions, and grand sill raised river bed around 50cm~100cm are aligned as the river bed modification case. Results of the simulation show the WUA increased gradually by the increasing river flow. WUA is decreased due to groundsill at low flow, but increased rapidly at high flow. Since groundsill thwarts the river flow at high flow that makes more suitable zone for aqua-habitat. When the river flow depletes, some of habitat are replaced by concrete groundsill, and suitable area decreased.

並列關鍵字

Ecological base flow ； Physical Habitat Simulation System ； Suitability curve

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