Groundwater flood of a river terrace in southwest Wisconsin, USA

Gotkowitz, Madeline B.; Attig, John W.; McDermott, Thomas

Groundwater flood of a river terrace in southwest Wisconsin, USA | Inondation par les eaux souterraines d’une terrasse fluvial dans le sud-ouest du Wisconsin, Etats Unis d’Amérique Inundación por agua subterránea de una terraza de un río en el sudoeste de Wisconsin, EEUU 美国威斯康辛州西南部河流阶地的地下水洪水 Inundação de águas subterrâneas de um terraço de rio no sudoeste de Wisconsin, EUA

2014

Gotkowitz, Madeline B. | Attig, John W. | McDermott, Thomas

Intense rainstorms in 2008 resulted in wide-spread flooding across the Midwestern United States. In Wisconsin, floodwater inundated a 17.7-km²area on an outwash terrace, 7.5 m above the mapped floodplain of the Wisconsin River. Surface-water runoff initiated the flooding, but results of field investigation and modeling indicate that rapid water-table rise and groundwater inundation caused the long-lasting flood far from the riparian floodplain. Local geologic and geomorphic features of the landscape lead to spatial variability in runoff and recharge to the unconfined sand and gravel aquifer, and regional hydrogeologic conditions increased groundwater discharge from the deep bedrock aquifer to the river valley. Although reports of extreme cases of groundwater flooding are uncommon, this occurrence had significant economic and social costs. Local, state and federal officials required hydrologic analysis to support emergency management and long-term flood mitigation strategies. Rapid, sustained water-table rise and the resultant flooding of this high-permeability aquifer illustrate a significant aspect of groundwater system response to an extreme precipitation event. Comprehensive land-use planning should encompass the potential for water-table rise and groundwater flooding in a variety of hydrogeologic settings, as future changes in climate may impact recharge and the water-table elevation.

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