Study On Influence Of Straightening On River Health

Straightening is a common form of river rebuilding. By Straightening, Human fixed excessive the flexuous river, reduced flood water level, shorten flood time, shorten flood process, improved the river navigation condition. But it changed the basic form of the natural river, led to the unknown influence of river safety and coast ecological system.In the last 20th century, river health concept was introduced by the foreign researchers. It is a systemic river theory. In this theory, the river was likened to the human body. The river was diagnosed in different angles and was assessed the effects of disturbed and degenerate. Accordingly it will propose measures to restore the river system for river management.This article assesses the influence of straightening on river health. Take Jiyun river (JiuWangzhuang ~ tide gate) as example, this essay mainly researched by establishing steady One-two dimensional hydraulics mathematic model and One dimensional water quality model and making numerical simulation. The research includes the following aspects:(1) The movement of water usually is an important factor of evaluating river health. Make use of the hydraulics indicators such as water level, flow rate, etc, to analyze the river's condition before and after the Straightening.(2) Field survey of the river water quality as the basic parameters, calculated by the model to assess the effects of water contamination before and after the Straightening.(3) Select the maximum scour depth of river to assess the stability of sediment, Make use of the improved erosion formula to calculate the results, and assessment of the stability of the riverbed.(4)The erosion of high-speed flow is an Important reason for structural instability of bank, In this study, the researcher calculated erosion for water that closed to the river, and analyzed the impact on the lateral erosion.(5) By comparing the hydrodynamic characteristics in the sites of Straightening, the researcher analyzed the aquatic biological communities and environmental conditions in the river, and evaluated the impact on the ecosystem diversity.