Groundwater and River Flooding: The Importance of Wetlands in Coastal Zones

Neri-Flores, I.; Moreno-Casasola, P.; Peralta-Peláez, L.A., and Monroy, R., 2019. Groundwater and river flooding: The importance of wetlands in coastal zones. In: Silva, R.; Martínez, M.L.; Chávez, V., and Lithgow, D. (eds.), Integrating Biophysical Components in Coastal Engineering Practices. Journal of Coastal Research, Special Issue No. 92, pp. 44–54. Coconut Creek (Florida), ISSN 0749-0208. The groundwater-surface water relationship in coastal floodplains is key to wetland management. Coastal floodplains are prone to river overflow and groundwater upwelling, so climate change may increase the vulnerability of people and infrastructure. This study was carried out on the coastal plain of Veracruz, Mexico where, in 2010, Hurricane Karl produced a river flood and the coastal city of Veracruz-Boca del Río suffered many losses. The objective was to understand river-groundwater flooding and how seasonality in local groundwater flow is related to flood type, site topography and the wetland vegetation in this coastal zone. To this end, 31 piezometers and time series flow data from two hydrometric stations were monitored monthly, and remote images were used to classify land use and vegetation. The frequency and extent of an extreme river flood (caused by Hurricane Karl in 2010) and groundwater flood were documented. The results show that the 2010 river flood can be classified as an extreme flood with a return period of 50-100 years, inundating 60.5% of the rural area, 39.5% of the natural vegetation and roads, and 4.8% of the city. Groundwater floods occur every year in the low-lying areas of the floodplain, which correspond to discharge zones covered by wetlands. Different flood types require different solutions; i.e. the identification of areas that can serve as river buffers to divert water during extreme events, and allowing wetlands to function as natural defenses to reduce flood impact. These solutions can reduce floods, as can proper city planning. Management plans should include both engineering solutions and should make use of the ecological functions of wetlands and floodplains.