  The need to attenuate hydrograph peaks is central to the design of stormwater
and flood control systems. However, few guidelines exist for siting hydraulic
control structures such that system-scale benefits are maximized. This study
presents a graph-theoretic algorithm for stabilizing the hydrologic response of
watersheds by placing controllers at strategic locations in the drainage
network. This algorithm identifies subcatchments that dominate the peak of the
hydrograph, and then finds the "cuts" in the drainage network that maximally
isolate these subcatchments, thereby flattening the hydrologic response.
Evaluating the performance of the algorithm through an ensemble of hydrodynamic
simulations, we find that our controller placement algorithm produces
consistently flatter discharges than randomized controller
configurations---both in terms of the peak discharge and the overall variance
of the hydrograph. By attenuating flashy flows, our algorithm provides a
powerful methodology for mitigating flash floods, reducing erosion, and
protecting aquatic ecosystems. More broadly, we show that controller placement
exerts an important influence on the hydrologic response and demonstrate that
analysis of drainage network structure can inform more effective stormwater
control policies.
