|dc.description.abstract||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.||en_US|