Understanding impacts of groundwater dynamics on flooding and levees in Greater New Orleans

Abstract

Study region: The Greater New Orleans in southeastern Louisiana, USA. Study focus: Flooding is a major threat to New Orleans due to its geographic location and geologic condition. However, potential groundwater flooding is seldom studied and poorly understood. This study investigated potential groundwater flooding and seepage-induced hazards to levees in New Orleans. High-fidelity stratigraphy and groundwater models were developed to investigate groundwater dynamics and identify areas prone to groundwater flooding and low levee factor of safety. New hydrological insights for the region: The stratigraphy model showed that 74 % of shallow sediments in New Orleans are fine grains and noticeable amounts of coarse sediments connect to surface waters. The groundwater model showed that shallow sands, such as beach sands and point bar sands, have strong hydraulic connections with lakes, canals, and Mississippi River. Groundwater flow simulation in 2018 found that 40 % of New Orleans metropolitan area may have groundwater level above ground surface all year round. Low-lying areas with relatively permeable surficial sediments and high groundwater head in shallow sands are concerned about potential groundwater flooding. The simulation results also indicated that levees in these areas have high probabilities of low factors of safety. Not only did the model prediction agree well to the previous levee assessments for the Hurricane Katrina disaster, but it also indicated additional areas with potential levee safety issues.

Keywords

• Groundwater flooding
• Modeling
• Seepage
• Levee
• New Orleans