Hydraulic modeling of the 2011 New Madrid Floodway activation: a case study on floodway activation controls

Engineered floodways are floodplains managed by hydraulic controls that can be activated passively, whereby the floodway fills and empties with changes in channel stage, or through a rapid control action, such as the detonation of a levee. During May of 2011, the Birds Point-New Madrid Floodway (NMF) was activated through levee detonation and the performance of this approach is examined herein. A two-dimensional hydraulic flood model (LISFLOOD-FP) is applied to the NMF and calibrated for April and May of 2011 in order to recreate the levee detonation scenario (detonation control). Additionally, the model is applied to simulate flood impacts had the NMF been activated passively, without the deliberate breaching of the levees (passive control). Results show that detonation control reduced flood stages upstream of the activation site by 0.8 m (2.62 ft) without significantly altering overall flooding extent compared with the passive control scenario. Damage estimates from the US Federal Emergency Management Agency HAZUS-MH model indicate that detonation control slightly reduced losses associated with building replacement costs and damaged crops (4.0 % reduction). However, floodway and levee damages that occurred under the detonation control required over 50 million US$ in repairs, and these costs would have been greatly reduced under a passive control scenario. These results indicate that the detonation control effectively reduced flood stage and the risk of upstream levee failures without increasing flooding extent, building losses, and crop damages, but the potential for floodway erosion and deposition deserves additional consideration in the implementation of a rapid activation design.