河川水利工程的生態環境考量是近年的趨勢，為了探討河川在洪水流況下魚類生存空間分佈，乃針對流速、水深的空間分佈進行研究。其要旨有四：一、為調查研究魚類的克服流速並探討卑南溪上游之新武呂段主要魚類的克服流速；二、為整理卑南溪實測流速水深資料，以迴歸分析求取水深、坡降、底床代表粒徑與流速之關係式作為流速分佈演算依據；三為研究如何以水理演算推算棲地水理參數通水斷面變化；四為繪製樣區河段等速線圖據以瞭解洪水流況下之棲地分佈。經以卑南溪主流上游之新武呂段例進行分析研究，所獲得之結果摘述如下： 1.卑南溪新武呂段的魚種體長與克服流速成正比，但具有吸盤的魚種可有更高的克服流速。2.0m/s流速以下區域為在洪水流況下魚類存活的棲地，2.0m/s流速為洪水中棲地流速上限。 2.在有較完整實測流速、水深、底質調查分析資料記錄的河川以迴歸分析求取水深、坡降、底床代表粒徑與流速之關係式作為流速分佈演算可行。卑南溪流速迴歸式：V=0.429D+84.135S+12.032n。 3.數位化河川地形及影像能較精確有效地支持棲地量測、地表參數估算及水理計算，並據以做為河川棲地水理演算、及正確展示流速空間分佈（包括等速線圖及箭向圖）。 4.以HECRAS水理分析模組推估河段各斷面水位。由水位與地表高程差求取水深。經由水深、坡降、底床代表粒徑與流速之關係式求取各點流速。再由2.0m/sec等流速線所圍區域即為洪水流況之棲地範圍。 5.在寬廣河段洪水流況下棲地面積會增加。以新武呂段隘口下游河床為例約增加為2.7倍，在峽谷河段則略減少。面積增減與河道地形有密切關係。流速2.0m/sec以下棲地沿高灘地、河中洲及兩岸緩坡邊緣分佈。邊坡越緩洪水時棲地面積增加越多。 Taking into account of the ecology environment factor in river engineering study has become a popular approach in recent year. As to discuss the distribution of the fish survival space in river flood, the space distribution of flow velocities and water depths are focused in the research. Four key points of this research are listed as follows: （1）To study the adequate flow velocities for fish species, and to discuss the overcoming velocity for the main fish species of Sinwu reach in upstream Panan River. （2）To rearrange the measured flow velocities and water depths of Panan River, and find out the flow velocity relationship with water depth, slope and typical particle size of riverbed by regression analysis. This relationship is the base for the computation of the flow velocity distribution. （3）To study how to estimate the changes of hydraulic parameters and flow cross-sections in habitat with hydraulic computations. （4）To plot the flow-velocity contour lines of the sample river reach as to find out the habitat distributions during flood condition. Based on the case study of Sinwu reach of main upstream Panan River, some conclusions are summarized as follows: 1.The body length of the fish in Sinwu reach of Panan River is proportion to the overcoming flow velocity. But fish species with sucking disks have higher overcoming velocity. The velocity of 2.0 m/s is the upper limit under flood condition. The habitat area with velocity below 2.0 m/s is survival region for the fish. 2.The computation of flow velocity distribution from the formula derived by regression analysis of the flow velocity with respect to water depth, slope and typical particle size of riverbed is doable for rivers that full with more data records of measured flow velocity, water depth and bed material investigation. Regression velocity formula of Panan River is V=0.429D+84.135S+12.032n。 3. Digital river topography and photo image can more effectively support the estimations of habitat location, ground parameter and area, and hydraulic computations. They can be also used for the hydraulic computation of the river habitat and the demonstrations for the velocity distributions in space (including equal-velocity lines and velocity vectors). 4.To estimate the water level at each cross-section with HECRAS hydraulic-analysis module. Find out the flow velocity at each point by the relationship of velocity with respect to water depth, slope and typical particle size of riverbed. The area within the 2.0 m/s velocity contour line is the habitat. 5.The habitat area will be increased at wide river reach under flood condition. For example, habitat area is increased to 2.7 times at the downstream riverbed of the narrow section of Sinwuri reach. It is a little bit decreased at the river canyon reach. The increase or decrease of the habitat area is closely related to the river topography. The habitat areas with velocity under 2.0 m/s are located along flooding areas, river bars and the mild side slopes of two river banks. Milder side slope increased more habitat area under flood condition.
