Landscape vulnerability to flood impacts in a human-dominated floodplain

The variable flood regime of a natural floodplain supports a variety of vegetation and habitat niches and regenerates the landscape through erosion and deposition. However, flooding of human-dominated landscapes are termed ``natural disasters'' due to potential devastating impacts such as the loss of lives and property, agricultural damage, or undesirable erosion and deposition. Natural hazards and climate change fields employ the vulnerability concept to assess various aspects of human susceptibility to disturbances or altered conditions. Vulnerability is generally defined as the likelihood of harm. It is a function of exposure, sensitivity, and adaptive capacity of a system. This study implements a mathematical framework, 2D flow modeling, and spatial mapping to present an analysis of vulnerability to erosion and deposition due to the activation of Bird's Point-New Madrid Floodway in May 2011. The historic pre-conceived levee breach and subsequent inundation of the agricultural floodplain represents a large-scale experiment to assess vulnerability of intensively managed landscapes to extreme events. Pre-flood and post-flood high-resolution Lidar topography datasets are analyzed and compared to vegetated land cover, soil properties, topographical legacies, and measured and modeled flow characteristics to quantify their potential contributions to vulnerability in the Floodway. It was found that the most significant erosional feature occurred at O'Bryan Ridge, an agricultural region at a low ridge formed by a historic meander of the Mississippi River. Areas of significant erosion corresponded to highly erodible soils, high simulated flows, and an absence of woody vegetation. Deposition throughout the Floodway was generally mitigated due to low river-to-floodplain connectivity and moderate sediment input from the river. Other relict meanders within the Floodway were found to be less vulnerable than O'Bryan Ridge due to lower flood exposure caused by gradients, vegetation, floodplain width, and backwater flooding. This analysis demonstrates the importance of vegetation for the protection of otherwise vulnerable regions. The methodology of this analysis can be used to locate regions of high vulnerability in future floodplain management to mitigate potentially catastrophic landscape change