Department of Geosciences, Colorado State University, Fort Collins, CO, USA.
Department of Geosciences, Colorado State University, Fort Collins, CO, USA.
Sci Total Environ. 2022 Sep 1;837:155773. doi: 10.1016/j.scitotenv.2022.155773. Epub 2022 May 7.
Despite the recognition of floodplain importance in the scientific community, floodplains are not afforded the same legal protection as river channels. In the United States alone, flood-related economic losses were much higher in the second half of the 20th century than the first half despite the expenditure of billions of dollars on flood defenses. Partially to blame are the low appraisal and understanding of human impacts to floodplain functions. Here, we explore the impacts of levees on floodplain functions and analyze case studies of floodplain restoration through levee removal. Floodplain functions include (1) fluxes of water, solutes, and particulate materials; (2) enhanced spatial heterogeneity of hydrology and biogeochemistry; (3) enhanced habitat abundance and diversity; (4) enhanced biomass and biodiversity; and (5) hazard mitigation. Case studies of floodplain restoration involving artificial levee adjustment are heavily concentrated in North America, Europe, and Japan, and those case studies assess floodplain functions within 30 years of restoration. In the United States, restoration through levee removal comprises less than 1% of artificial levee length and 1-2% of disconnected floodplains. In Europe, restoration effectiveness was severely limited by upstream flow regulation. Most case studies were impacted by stressors outside the study site and took place in lowland alluvial rivers. Reconfiguration was successful at achieving limited aims while reconnection set floodplains on a trajectory to more fully restore floodplain functions. Case studies illustrated the tension between restoration scale and study resolution in time and space as well as the role of site-specific characteristics in determining restoration outcomes. Numerous knowledge gaps surrounding the integrative relationships between floodplain functions must be addressed in future studies. The ubiquity of flow regulation demands that future floodplain restoration occur in a whole-of-basin manner. Monitoring of restoration must take place for longer periods of time and include multiple functions.
尽管科学界已经认识到洪泛平原的重要性，但洪泛平原并没有像河流渠道那样得到同样的法律保护。仅在美国，尽管在防洪方面花费了数十亿美元，但 20 世纪后半叶的洪水相关经济损失远远高于前半叶。部分原因是对人类对洪泛平原功能的影响的评估和理解较低。在这里，我们探讨了堤坝对洪泛平原功能的影响，并分析了通过拆除堤坝进行洪泛平原恢复的案例研究。洪泛平原的功能包括：（1）水、溶质和颗粒物质的通量；（2）水文和生物地球化学的空间异质性增强；（3）栖息地丰富度和多样性增加；（4）生物量和生物多样性增加；以及（5）减轻灾害风险。涉及人工堤坝调整的洪泛平原恢复案例研究主要集中在北美、欧洲和日本，这些案例研究在恢复后 30 年内评估了洪泛平原的功能。在美国，通过拆除堤坝进行的恢复不到人工堤坝长度的 1%和断开的洪泛平原的 1-2%。在欧洲，恢复效果受到上游流量调节的严重限制。大多数案例研究受到研究地点以外的压力因素的影响，并且发生在低地冲积河流中。重新配置在实现有限目标方面取得了成功，而重新连接使洪泛平原走上了更全面恢复洪泛平原功能的轨道。案例研究说明了在时间和空间上恢复规模和研究分辨率之间的紧张关系，以及特定地点特征在确定恢复结果方面的作用。未来的研究必须解决围绕洪泛平原功能之间综合关系的众多知识空白。泛滥平原功能的整体关系必须在未来的研究中得到解决。恢复监测必须在更长的时间内进行，并包括多个功能。
