LWI Region 3 Modeling Overview

6.2 BAYOU COCODRIE 6.2.2 Concept 1: City of Vidalia Pump Station

{ Flooding in Vidalia and Ferriday is caused by slow drainage and backwater from Bayou Cocodrie during heavy rain events (Figure 6-4). { A new channel and pump station were added to move excess water directly from Vidalia Canal to the Mississippi River. { The pump station includes two pumps (800 cfs each) and activates early at 25 ft water elevation to handle peak rainfall effectively. { An existing channel between Hoover Slough and Vidalia Canal was graded to help redirect water from Ferriday into the new system. { The updated model showed water levels dropped by up to 1.6 ft in Vidalia Canal and nearby streams, though urban areas saw little change due to limited drainage capacity and inadequate structures. (Ref: see Cocodrie Proof of Concept Report)

Figure 6-4: Proposed plan and comparison of water depths between calibrated result (before) and the proposed concept result (after) at key locations near the City of Vidalia and the Town of Ferriday.

6.2.3 Concept 2: Canal and Lake Sediment Removal

{ Due to the relatively flat channel slope and significant overland flooding, coupled with restricted outflow in Bayou Cocodrie, a backwater effect causes slow water movement ( Figure 6-5). { This concept helps reduce flooding by redirecting stormwater from Vidalia, Ferriday, and nearby areas into Cocodrie Lake, then to Black Lake, and finally out to the Black River. { Cocodrie Lake was lowered from 33 ft to 22.5 ft to match the Cross Cocodrie bayou's low point (survey data), allowing water to flow smoothly into the lake.

{ Black Lake was lowered from 30 ft to 19 ft , and the channel between the two lakes was reshaped to keep water moving efficiently. { Vidalia Canal was slightly improved by removing up to 2 ft of sediment and widening it by about 20 ft to increase flow and storage capacity. Structures along Vidalia canal were also widened. { A flap gate that was added near Black Lake (5,000 cfs capacity) helped water exit into the Black River, reducing water levels in lakes and canals - but no change in water level in urban areas due to limited city drainage systems. (Ref: see Cocodrie Proof of Concept Report) (Figure 6-6).

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LWI REGION 3 TRAINING

LOUISIANA WATERSHED INITIATIVE