Due to increases in land development, insufficient stormwater conveyance systems, and worsening tail water conditions due to sea level rise, there are significant drainage problems in the W-14 Basin resulting in significant street and structure flooding during severe rain events. DDG worked with St. Tammany Parish Government to obtain HMGP grant funding to reduce the risk of flooding for people residing in the W-14 basin while simultaneously reducing the marsh loss rates in the Fritchie Marsh.
The DDG team utilized an unsteady state HEC-RAS model of the W-14 Basin to evaluate the extent of existing flooding and to conduct an analysis of project alternatives. Flood reduction will be accomplished by widening approximately 3,250 feet of the W-14 Canal and constructing a regional detention pond to mitigate increases in downstream discharge resulting from improved conveyance. Based on the numerical model results, DDG performed a Benefit Cost Analysis (BCA) for the W-14 Basin to secure funding of the identified drainage improvements.
In addition to the HEC-RAS modeling, a 2D water surface model (MIKE FLOOD) of the Fritchie Marsh was developed in coordination with the Water Institute of the Gulf. Wetlands will be enhanced in the future by improving conveyance of freshwater and nutrients from the W-14 Basin to the Fritchie Marsh. DDG continues to coordinate with state and federal agencies through the CWPPRA program to improve the circulations patterns and therefore the health of the Fritchie Marsh.