Feedback between Reservoir Operation and Floodplain Development: Implications for Economically Efficient Use of Floodplains and Reservoir Storage

Abstract:

Currently, reservoir operation researchers and decision-makers weigh the trade-off between water conservation and flood control at the event and seasonal scales. However, socio-economic pressures on reservoir operation in the distant future can be shaped by present infrastructure development and operational decisions, thus warranting their inclusion for present decision analysis. Here, we explore the particular case of feedback between reservoir operation and downstream floodplain development (see figure) by modifying and uniting mathematical frameworks which had previously been isolated. Compared to existing studies of floodplain settlement, this study addresses the novel complication that increased flood protection via changes to reservoir operation comes at the expense of water conservation. We show that as time goes on under a status quo operating policy (i.e. maximizing expected benefits at the event-to-seasonal-scale) (1) systems evolve toward highly developed floodplains and high operational preference for flood control, (2) benefits shift from water conservation consumers to floodplain inhabitants, and (3) less net benefit is achievable. Further, we compare the status quo operating policy to a policy which stabilizes the floodplain development level and show that allowing excess (i.e. more than is optimal at the seasonal scale) flooding now preserves future water conservation benefits by disincentivizing floodplain development. Finally, we illustrate this co-evolution and its ramifications at two U.S. reservoir-floodplain systems where floodplain development has seemingly undermined hydropower production. The insights from this study are essential (though not sufficient) to achieving economically efficient use of floodplains and reservoir storage, such as is sought in U.S. House Document 465, where an “effective approach” to flood control is deemed one where “the full costs of flood plain occupance would be shifted to the prospective occupants themselves”.