10. NUMERICAL MODELING
PRECIPITATION
Average Precipitation per Month
8
7
Average Monthly Precipitation (in/month)
6
5
4 Statistical Averages:
• Wet Days = 109 days/year
3 • Dry Days = 251 days/year
• Daily = 0.2 in/day
• Monthly = 5.2 in/month Abita Springs, LA Monthy Precipitation (in)
2
• Yearly = 62.7 in/yr Covington, LA Monthy Precipitation (in)
1 • Longest Drought = 51 days
• Longest Wet Period = 15 days Slidell, LA Monthy Precipitation (in)
0
January February March April May June July August September October November December
Common period of 1973 to 2010
13. NUMERICAL MODELING
EVAULATION CRITERIA
• Increased Flow Constrictions
• Changes to Topography and Canopy
• Impacts to Wetlands
• Variations to Ponding (Inundation)
• Variations to Drought (Drying)
• Water Level Fluctuations
• Changes to Sedimentation and Nutrient Loading*
*Not quantified due lack of channel survey data. Sediment depostion, pollutant
accumulation, and nutrient discharges must be investigated during design phase
14. NUMERICAL MODELING
FLOW CONSTRICTIONS
• Most Common Flow Constriction = Hydraulic Structures
• 118 Structures Modeled in LADOTD Hydraulic Software
• Peak Flows Determined using HEC-HMS
• Scores Evaluated:
• Type of Structure
• Size of Structure
• Proposed Structure would Replace an Existing Structure
15. NUMERICAL MODELING
TOPOGRAPHY/CANOPY CHANGES
• Scores Evaluated:
• Roadways Constructued on Undeveloped Land
• Roadways Constructued on Existing Roadways and Abandoned
Railways
16. NUMERICAL MODELING
DIRECT WETLAND IMPACTS
• Wetlands Delineated by Tetra-Tech within 250 ft Right-of-Way
• Scores Evaluated:
• Wetland Acres within Right-of-Way
17. NUMERICAL MODELING
PONDING/DROUGHT VARIATIONS
• Duration an Area Remains Submerged is a Critical Parameter
Impacting Functionality of Wetlands
• Ponding Duration Leads to Changes in Wetland Type, Function, and
Quality
• Ponding/Drought: Changes to Water Surface Extent or Inundation
• Scores Evaluated:
• Ponding: Inundated Areas Compared to Existing Conditions
• Drought: Dry Areas Compared to Existing Conditions
21. NUMERICAL MODELING
WATER LEVEL FLUCTUATIONS (2-YEAR STORM EVENT)
• Difference in Maximum and Minimum Water Levels in a Wetland
• Changes in Wetland Water Level may cause a Consistent Delince in
Diversity and an Increase in Invasive Species
• Scores Evaluated:
• Change in Water Suface Exceeded 0.025 m
25. CONCLUSIONS
Hydrodynamic Numerical Model
Alignment Evaluation with Categorical Rating System
Dominant Factors of Constructing Roadways through Wetland
Systems:
• Roadway Placement and Orientation
• Basin Gradient
• Channel Crossings
