Objective The downstream channel of Yongding River was occupied and damaged seriously after it was dry from the 1980s. Ecological water replenishments were carried out in 2019 and 2020 for river ecological restoration. The reach between Wanping Lake and Huangliang Railway was selected to simulate the river morphology under different ecological flows and pulse flows. This paper aims to couple different flow discharges with the river spatial morphology to provide information for ecological restoration.
Method (1) Ecological flow discharges of different habitat conditions were calculated by Tennant method. And three ecological flow discharges and four pulse flow discharges were selected and set as the hydrology inputs for simulation. (2) The river morphology characteristics under flow discharges above were modelled by CAESAR-Lisflood model.
Result (1) The simulation results under different ecological flows were: the annual average wetted areas were 439.29−462.74 ha, water surface heights were 40−52 m, the Max. velocities were 1.49−2.24 m/s, the erosion areas were 52.18−77.94 ha, and the deposition areas were 61.70−101.39 ha. The results under different pulse flows were: the wetted areas were 637.58−769.25 ha, water surface height was 42−55 m, and the Max. velocities were 3.92−5.85 m/s. (2) The restoration alternatives were suggested according to the river spatial morphology characteristics. And the erosion/deposion areas and the flooding areas under 5-year return period flood were identified as the resilient space.
Conclusion The study reach and the whole dry downstream of Yongding River in Beijing should be ecologically restored by natural recovery and artificial restoration measures under the implementation of ecological water replenishment. It is necessary to make space for nature to heal itself and for river dynamic processes. And it needs long-term monitoring and adaptive management strategies to rebuild the ecosystem function and the natural river landscape in the future.
DownLoad: