Application of submerged groin systems in the ecological restoration of littoral zones
潜水丁坝在湖滨带生态恢复中的应用

Strong lake current scouring caused by wind and scarcity of soft sediment make hydrophytes hard to grow near the lakeshore in Meiliang Bay of Taihu Lake. Based on field survey and laboratory simulation, 14 submerged groins were designed and constructed in the eroded shoreline of Meiliang Bay for protecting and stabilizing the lakeshore ecosystem. The length of each groin was 23 -28 m and the distance between the adjacent groins was 40 - 80 m. Seedlings of pioneer plants including Phragmites australis and Zizania caduciflora were planted on the groins. Results showed that the submerged groin systems could withstand the strong wind attack and scouring of lake currents. The original reed belt along the lakeshore extended 2 - 5 cm lakeward per year under certain water levels. Some hydrophytes grew naturally on the groin field. Benthic organism such as freshwater snail reproduced massively and many birds liked to perch on the groin area. The groin systems made sediments accrue in the predefined area along the shoreline. Sediment trapping experiments showed that the sediment accretion in the vegetated groin field was significantly higher than that in the bare zone without vegetation. As a result, the accreted sediments created physical conditions for the growth and reproduction of aquatic plants. It was found that the submerged groin systems could trap bluegreen algae effectively under the mild wind, and thereby protect the water quality of drinking water sources. The combination of constructing submerged groins and growing plants on them provided a tentative scheme for ecological restoration in the littoral zones.