Restoring Rivers and Floodplains for Habitat and Flood Risk Reduction: Experiences in Multi-Benefit Floodplain Management From California and Germany

Abstract

Conventional flood control has emphasized structural measures such as levees, reservoirs, and engineered channels—measures that typically simplify river channels and cut them off from their floodplain, both with adverse environmental consequences. Structural measures tend to be rigid and not easily adapted to increased flooding regimes resulting from environmental change. Such actions also limit the natural hydrologic benefits of floodplains such as storing floodwaters, improving water quality, providing habitat for invertebrates and fish during periods of inundation, and supporting a multitude of cultural services. As these benefits are more widely recognized, policies are being adopted to encourage projects that reduce flood risks and restore floodplain ecosystems, while acknowledging the social-ecological context. The number of such projects, however, remains small. We assessed four multi-benefit floodplain projects (two in California, United States, and two in Germany) and characterized their drivers, history, and measures implemented. In both United States cases, the dominant driver behind the project was flood risk reduction, and ecosystem restoration followed, in one case inadvertently, in the other as a requirement to receive a subsidy for a flood risk reduction project. One German case was motivated by ecosystem restoration, but it was more widely accepted because it also offered flood management benefits. The fourth case was conceived in terms of balanced goals of flood risk reduction, ecosystem restoration, and recreation. We conclude that projects that both reduce flood risk and restore ecosystems are clearly possible and often cost-effective, and that they could be more widely implemented. The principal barriers are often institutional and regulatory, rather than technical.

The Social, Economic, and Ecological Drivers of Planning and Management of Urban River Parks

“…Furthermore, the high level of urbanization of the floodplain after the construction of the dams makes it difficult to remove the dams and reestablish the flow of the river while protecting the people and their communities. However, some of examples of multi-benefit projects like nature based-solutions to reduce flood risk exist, such as the Bear River levee setback in California, but they are still rare (Serra-Llobet et al, 2022). The limitations of flood protection from dams and reservoirs are well-established in the scientific community.…”

Shifting Trade-offs: Finding the Sustainable Nexus of Hydropower and Environmental Flows in the San Joaquin River Watershed, California

“…Ameliorating this challenge may seem less daunting once the ecological (and human) benefits of prioritized environmental flows are accounted for (Richter and Thomas 2007). Although such changes might incur short-term one-time costs to implement (e.g., relocating communities built in floodplains to allow for improved floodplain services), the long-term benefit to ecological and human communities may make such efforts worthwhile (Tickner et al, 2020;Serra-Llobet et al, 2022).…”

“…Thus, environmental flow policies should align with other policy objectives, such as the recent Sustainable Groundwater Management Act (AB 1739, SB 1168, and SB 1319, to ensure the full range of ecosystem functions are achieved (Yarnell et al, 2022). Pairing winter peak flow releases with groundwater recharge and reconnected floodplains, either through multi-objective land use strategies (e.g., the Yolo Bypass, an important floodwater-groundwater interchange north of the study region) or managed retreat of developed riparian lands (Dybala et al, 2019) could be a strategy to achieve synergistic conservation goals (Serra-Llobet et al, 2022). Enhanced environmental flows for groundwater dependent ecosystems is one benefit of agricultural managed aquifer recharge (ag-MAR; Damigos et al, 2017;Levintal et al, 2022), including the San Joaquin watershed (Kourakos et al, 2019;Alam et al, 2020;Levintal et al, 2022).…”

The role of soil and plant cover as drivers of soil macrofauna of the Dnipro River floodplain ecosystems

“…Solving the problem of managing floodplain ecosystems that are under anthropogenic influence is possible based on an understanding of the interactions between the various biotic components of ecosystems and soil cover (Schindler et al, 2016;Vári et al, 2022). The important role in procedures of development of optimum management strategies is played by protected floodplain ecosystems, which can be considered as a reference pattern of interaction between various components of an ecosystem (Kiedrzyńska et al, 2015;Serra-Llobet et al, 2022).…”