Computationally Assessing the Effect of Dam Operation on Flood Hazard

Abstract

Flood protection assets such as dams are increasingly seen as part of a larger system, but the complexity of dam management, unclear communication, and operational misunderstandings in operational protocols can lead to unnecessary downstream flooding. This paper investigates how human factors, such as dam operators' communication and roles and responsibilities, influence flood flows. Using HEC-RAS, the study varies initial reservoir volume and pre-release duration in four New Zealand catchments, with potential for adaptation in other areas. The results found: (i) dams designed to provide flood storage had stronger correlations between the duration of pre-releases and outflow reductions, (ii) dams with large storage capacities and fewer release mechanisms had stronger correlations between the initial reservoir volume and outflow reductions, (iii) a dam's ability to appropriately control flow is governed by the presence and implementation of clear operating procedures shown by the dam mandated to provide flood storage having the highest consistency in flow reduction and a 6% difference in maximum dam outflow between best and worst-case operations, and (iv) mismanagement of outflows can increase downstream flooding; in one catchment, the outflow was 38% above the inflow. The results are widely applicable given the increasing importance of flood control mechanisms and operational protocols.