Trade-Offs and Synergies in Floodplain Management: A Historical-Ecological Approach

Floodplains have long been favored sites for agriculture and settlement due to their fertility, flat topography, and proximity to rivers for easy transport of goods. To reduce flood risk in settled floodplains, extensive networks of levees and other flood protection structures have been built. These modifications have greatly reduced the ecological benefits that intact river-floodplain systems provide. There is increasing recognition that floodplain reconnection can restore some ecological benefits while further reducing flood risk. However, few of these promising multi-purpose projects have been implemented because we lack both practical methodologies for estimating benefits and an understanding of social conditions likely to facilitate project success.

Here, we use both historical and biophysical approaches to examine the trade-offs and synergies among the benefits of a proposed floodplain reconnection project in Napa, California. We examine the social evolution of attitudes and views that shaped floodplain management decisions, and that led to moments of conflict and cooperation among actors with varied interests. We also use hydraulic and population models to predict the effect of floodplain reconnection on key ecological benefits, flood risk, and availability of land for agriculture. In combination, these approaches demonstrate how social and biological forces constrain and provide opportunities in floodplain management. This understanding will inform effective implementation of multi-purpose floodplain restoration projects.