基于淤涨速率的潮滩围垦适宜性评价

Evaluation on the suitability of mud flat reclamation based on intertidal morphodynamics

潮滩既具有重要的生态服务功能,亦是潜在的土地资源。过去几十年来,中国沿海潮间带的开发以围垦为主要驱动力,表现为海岸线主体向海推进。随着围垦规模和速度加快加大,出现了一系列生态、环境及土地利用问题,因此对于围垦适宜性的研究具有现实意义。本文以浙江省为例,利用遥感技术首先获取了大陆海岸线阶段性变化特征。接着从地貌均衡的角度,依据潮滩垂向淤涨速率和垂直岸线的潮滩剖面形态估算适宜的潮滩围垦速率。最后,比较海岸线实际推进速率与估算所得的围垦适宜速率,进行围垦适宜性分级评价。研究表明,1985-2015年间,围垦活动是浙江省大陆海岸线向海推进的主要原因。从时间进程来看,1985-1995年浙江省大陆海岸线向海推进缓慢,受围垦活动影响较小;1995-2015年间围垦活动频繁,人工岸线比例增加较多。围垦适宜速率的估算显示,杭州湾南岸围垦1 km后所需恢复时间最短,围垦适宜速率为12.5~64.3 m/a,其次为象山港和台州湾,围垦适宜速率分别为2.0~38.3 m/a和6.0~22.2 m/a;三门湾和温州湾围垦后所需恢复时间最长,围垦适宜速率分别为1.2~18.5 m/a和1.7~3.8 m/a。基于潮滩淤涨速率的围垦适宜性评价表明,1985-2015年间,浙江省主要围垦区域中围垦速率过快的是三门湾的下洋涂、蛇蟠岛和温州湾岸段,围垦速率较快区域为杭州湾南岸庵东浅滩部分岸段和象山港的莼湖镇、涂茨镇岸段以及台州湾的南洋涂,围垦速率略快的是庵东浅滩以及台州湾的北洋涂,围垦速率适宜的岸段仅有象山港的高湖塘和蒲门村岸段。浙江省过去30年的围垦进程和岸线变化启示,围垦活动应充分考虑潮滩环境的地貌动力均衡和自然恢复潜力。

The mud flat as potential land resource,has important ecological service function.In the past decades,reclamation has been the main driving force for the development of intertidal zones along the coast of China,which resulting in the coastline progressing towards the sea.With the increase of reclamation size and speed,a series of ecological,environmental and land-use problems appear,so it is of practical significance for the study of reclamation suitability.Taking Zhejiang Province as an example,this paper firstly collected the change characteristics of the mainland coastline between 1985 and 2015 by using remote sensing technology.Then,from the perspective of geomorphological equilibrium,the feasible reclamation rate of tidal flat is estimated according to the vertical siltation rate of tidal flat and the tidal profile shape of vertical shoreline.Finally,the propelling speed of coastline was compared with the estimated feasible reclamation rate,and the reclamation suitability was graded.The results show that reclamation is the main reason for the coastline of Zhejiang Province to move towards the sea from 1985 and 2015.In terms of time,during 1985 to 1995,the coastline of Zhejiang mainland pushed slowly toward the sea and was less affected by reclamation activities.During 1995 to 2015,reclamation activities were frequent,and the proportion of artificial coastline increased.The estimation of the reclamation feasible rate shows that the recovery time of the south coast of Hangzhou Bay is the shortest after 1 km reclamation.The feasible reclamation rate of south coast of Hangzhou Bay is 12.5~64.3 m/a,followed by Xiangshan Harbour and Taizhou Bay which feasible reclamation rates are 2.0~38.3 m/a and 6.0~22.2 m/a.Sanmen Bay and Wenzhou Bay need the longest recovery time after reclamation,and the feasible reclamation rates are 1.2~18.5 m/a and 1.7~3.8 m/a respectively.The evaluation on the suitability of mud flat reclamation based on intertidal morphodynamics shows that from 1985 to 2015,in the main reclamation areas of Zhejiang Province,the areas with excessive reclamation rate are Sanmen Bay,Shepan Island and Wenzhou Bay,and the areas with relatively fast reclamation rate are part of Andong tidal flats in the Southern Coast of Hangzhou Bay and Chunhu Town,Tuci Town in Xiangshan Port,and Nanyang tidal flats in Taizhou Bay.The areas with slightly faster reclamation rate are Andong tidal flats and Beiyang tidal flats in Taizhou Bay,while only the reclamation rate of Gaohutang and Pumencun are feasible.Enlightenment from the reclamation process and coastline changes in Zhejiang Province during past 30 years indicates that reclamation activities should take full account of the geomorphological dynamic balance and the potential of natural restoration of tidal flat environment.