The urbanization of coastal areas have been growing during the last century. However, several areas are going to affected by both marine flooding and groundwater flooding (or inundation) triggered by high tide due to the significant increasing trend of sea level. The latter is generally neglected in flooding forecasts. However, accounting for it, the total interested area may exceed twice that due to only marine flooding. Therefore, groundwater flooding will play a major role in the determination of coastal area potentially affected by flooding. In this work, a study on the modeling of groundwater flooding in an urban coastal area under various sea level rise (SLR) scenarios is presented. The urban laboratory of the city of Hoboken (NJ) was selected. It is located at the estuary of the Hudson River and has features common to several low-laying urbanized areas. For the simulations, the watershed of the city of Hoboken was built using a large variety of dataset from public and private sources as well as field measurements and then implemented in the open-source software MODFLOW. The model domain comprises subsurface geological structure representing the porous medium and a superficial layer to account for the urban ground hydraulic characteristics (Figure 1). Previous work in our group was carried out on the evolution of the groundwater table in response to tidal variation of the river to identify if inundation of aging infrastructure were possible. Results show that currently more than 60 % of the sewer may experience approximately groundwater infiltration for a total of 50 % of excess water within the system. Extension of this work was performed to predict the emergence of the groundwater above ground. Preliminary results on groundwater prediction, considering only tidal impact at the shore under various SLR scenarios, shows that within 20 years 40 % of the city streets could be flooded by groundwater in dry weather if no measures are taken to mitigate the impact of climate change.

Groundwater flooding in coastal urban areas

2019 Fall National Meeting

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