LWI Region 3 Modeling Overview

6 Proof of Concept

6.1 CITY OF MONROE 6.1.1 Boeuf Watershed – Young's Bayou Flood Mitigation Scenario As part of the Boeuf Watershed study, a detailed proof-of-concept flood mitigation scenario was developed for Young’s Bayou, a key tributary flowing through the City of Monroe. This bayou is particularly vulnerable to backwater from Bayou Lafourche and elevated stages along the Ouachita River, which can overwhelm existing drainage infrastructure and lead to flooding in southern neighborhoods of Monroe.

To address this situation, a suite of structural measures was implemented in the model to evaluate the potential flood reduction benefits: Southern levee along Young’s Bayou: Pump station on main channel: Channel widening and concrete lining:

A levee was constructed on the right (southern) overbank of the bayou to prevent lateral spread of floodwaters into residential neighborhoods south of the channel. This levee serves as the first line of defense against overland backflow.

To maintain conveyance while the gate is closed, an 800 cfs pump station was placed directly on the main channel of Young’s Bayou. This pump activates when the gate is shut and allows continuous discharge into Bayou Lafourche during backwater conditions. A dedicated detention pond was created adjacent to the bayou for temporary stormwater storage. This pond functions as an overflow reservoir during major rain events, receiving diverted flows from Young’s Bayou and reducing immediate peak volumes. Detention basin development:

A 4-mile stretch of Young’s Bayou downstream of the proposed pump was widened by 15 ft and lined with concrete to enhance conveyance capacity. The Manning’s roughness was reduced to 0.025 to reflect the hydraulically efficient surface. This modification alone contributed significantly to the reduction in flood stages, as illustrated in Figure 6-1.

Flap-gated control structures:

Within the main channel of Young’s Bayou, a new gate was added to prevent backwater flow from Bayou Lafourche. This gate automatically closes when downstream stages in Bayou Lafourche exceed channel elevation, ensuring upstream water remains contained.

Figure 6-1: Example of a typical cross section for channel widening and concrete lining for 4 miles of Young’s Bayou.

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LWI REGION 3 TRAINING

LOUISIANA WATERSHED INITIATIVE