LWI Region 3 Modeling Overview

c. Hydraulic Model Calibration and Validation Regional Calibration Approach Calibration was performed regionally using the previously grouped models (e.g., BF-East, BF-West, BF-South) and later integrated into one fully connected model to assess system-wide performance. Figure 3-24 shows the full model domain for calibration. Key calibration regions included:

• The Boeuf-Bayou Lafourche split at Gunby Dam • Urban Monroe (internal drainage and pumping systems)

Figure 3-23: Highlighting the Irwin Lake Dam that plays a crucial role in diverging flow on the Boeuf and Bayou Lafourche Rivers.

• Upper Boeuf River near the AR/LA Stateline • Boeuf River and Bayou Lafourche diversion

Additional inflows from Region 2 (Bartholomew/ Ouachita) were introduced to capture real-world, cross basin effects. Geometry Refinement During Calibration { All 1D elements were removed and replaced with 2D ROM components to avoid loss of interaction. { Culverts and conveyance paths were added or adjusted based on overtopping discrepancies between modeled results and known high water mark locations. { Manning’s roughness coefficients (n values) were tuned using land cover data and further adjusted to match timing and volume at gages. Final values ranged from 0.035 in channels to up to 0.15 in wooded floodplain areas. LEARN MORE: B_5.6 + Initial Condition Setup For each calibration event, three initial soil saturation conditions were available: 20%, 50%, and 80%, corresponding to dry, moderate, and wet antecedent conditions respectively. These conditions affected the initial deficit in the infiltration model. Table 3-3 provides the maximum and initial soil deficits used for infiltration modeling. LEARN MORE: B_4.6 +

Figure 3-24: Full model domain for Boeuf Watershed calibration showing key streams and gages.

{ For Silt Loam soils, this resulted in initial deficits of 7.12,” 4.45,” and 1.78” for each scenario. { Initial water surface elevations were set using baseflow conditions or warm-up periods to reach steady states before simulation start.

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Hydrologic and Hydraulic Modeling Methodology