八掌溪由於流路短、地勢陡峭，且全年雨量分配不均，形成枯豐水期差異明顯，更因上游集水區經濟作物之開闢，住宅、道路、遊樂區等人工設施持續大量開發，致使豐水期所降之雨量無法滲入地下而直接逕流，影響地下水之補注，造成枯水期水量嚴重不足，影響河中生態環境至巨。 本研究希望透過河川現有空間環境及生態環境，以既有河工構造物及自然氣象水文條件下，在八掌溪觸口橋至軍輝橋段河床渠槽中，利用以往所調查河中魚類、水生昆蟲類、藻類、兩棲類、鳥類及植物類等棲地內生物之種類、習性與數量及其歷年變化情形，透過比較與鄰近河川水中生物之差異性及其可能變遷情況，加以歸納整理，並將本研究河段依據不同河床性質、坡降、斷面及其所對應之現有環境概分為四個區段，並以三十年來之河川最大日流量及最大瞬時流量，加以研究分析評估其對河床及棲地破壞之情況以及其可能對水中生物之影響，提出解決改善方案，且採用國內外對魚類研究相關資料，重新建構適宜台灣河川水文條件之魚類生態基流量與生態高流量，並以三十年來每隔五年之全年日流量，加以比對評量分析八掌溪流量是否適宜魚類等生物生存環境，及其所產生之要因，並提出改善方案，且採用研究河段內之觸口橋及軍輝橋三十年來每年之泥砂含量，分析研究河段上游流域沖刷情形及研究段內河床沖刷情形，做分析比較泥砂對棲地環境變化之影響，且調查研究河段之水工構造物攔河堰及固床工，透過水理分析、現況分析、河床底質調查及全國類似河工構造物調查，加以分析檢討形成原因及對水中生物之影響，並尋求改善方案，以重新建立八掌溪生物多樣性生活環境，使其回復原有自然河川風貌。 Because Bajhang River is short with small drainage basins and is steep with uneven rainfall distrubition through out the year, the difference between dry and wet seasons is very noticable. The economic development, residential dwellings, roads, theme parks and other construction are continuously getting developed in the upper stream catchment area and this has caused the rainfall to direct runoff and not able to infiltrate the ground. This has affected the recharge of the ground water and caused the shortage of water volume in dry seasons and this influenced the river habitat greatly.This research is hoping to analyse and summarise the differences and likely changes of the living creatures such as fishes, river insects, algages and amphibians, birds and plants in the habitat between Chuko bridge and Chinhui bridge along Bajhang river by compared with living creatures in the close by rivers using the current space and habitat environment and based on the existing hydrological construction,geological and hydrological conditions and using the previous research on the type, quantity, habits and changes over the years. This research will divide the area of river under this research into four parts according to the differences in river bed, slope, section, and current environment and analyse and evaluate the damage and erosion of habitat and river bed and the effects it brings to living creatures in the river based on the maximum daily and instant discharge for the last 30 years. This research will attempt to come up with solutions to improve the situations. This research will also attempt to come up with the Fish's ecological flow of base and high flow of ecology that are suitable for the hydrological environment in Taiwan based on the relevant research on fishes conducted domestically and internationally.And the flow of day of the whole year every five years over the past 30 years to analyse and evaluate whether the daily discharge volume of Bajhang is providing a suitable living habitat for fishes and other creatures in the river. It will attempt to find out the cause of this daily discharge volume and come up with suitable solutions. The research will also look at the yearly sediment amount in the last 30 years for the area of the river under this research to analyse the erosion situation in upper stream and river bed and evaluate the effects sediment bring to the changes in the living habitat. The research will investigate the Construct things and block the river weir and firm bed worker in water conservancy project in the particular part of the river under research by using hydrological analysis, Similar to the river conservancy worker and construct things to investigate in present situation analysis , riverbed bottom quality investigation and the whole country and further analyse the effects The river conservancy worker constructs things brings to the living creatures in the habitat to come up with suggestions for improvements to re-establish the multi-dimensional living environment in Bajhang river and restore its nature.
