The Lacombe area has experienced flooding during several storm events causing repetitive flooding of structures. The Bayou Lacombe Regional Detention Pond was conceptually sized as a 110-acre pond in 2014 through an independent water quality study. The project includes developing the concept designs further by preparing a detailed two-dimensional (2D) Hydrologic and Hydraulic (H&H) model of the Branch Bayou – Lacombe Bayou and the Bayou Lacombe HUC 12 watersheds (±42,000 acres). Intracoastal is preparing the H&H model to support the design of the project.

As a part of Intracoastal’s initial task (Task Order #1), a Data Gap Analysis was performed to guide the Model Approach and develop the Design Criteria for the 2D H&H model. Intracoastal reviewed previous models prepared by St. Tammany Parish as well as the Louisiana Watershed Initiative’s (LWI) Region 7 model. The model approach developed will utilize the LWI model and clip it to the two HUC 12 watersheds within our focus area to build our detailed model for assessing the benefits of a regional detention pond. This approach saves the parish both time and money by reducing the level of effort required to collect data within the watershed and for developing the 2D H&H model.

Upon approval of the Model Approach and Design Criteria, Intracoastal will prepare the 2D numerical model (Task Order #2) through HEC-HMS and HEC-RAS. The model will include site-specific data collected for the project to update the LWI model geometry and for sizing the pond, inlet channel, and outfall structure. This will be compared against the Finished Floor Elevations (FFE) of low-lying structures within the study area to determine the benefits of the pond