state of the coast 2012
TRANSCRIPT
Experience │ Innovation │ Results
Jeanne C. Hornsby, MS, PE Robert L. Miller, MS, PE Justin M. Shaw, MS, PE
STATE OF THE COAST 2012
PRESENTATION OUTLINE
1) Project Description
2) Acknowledgements
3) Model Setup
4) Model Results
PROJECT LOCATION I-12 TO BUSH, LA
AGENCIES AND CONSULTANTS ENVIRONMENTAL IMPACT STATEMENT
DATA COLLECTION AGENCIES AND CONSULTANTS
LSU Atlas
PROJECT LOCATION EXISTING DRAINAGE BASINS
PROJECT EXTENTS EXISTING FLOW PATTERNS
PROJECT EXTENTS FEMA FLOOD HAZARD ZONES AND WETLAND AREAS
PROJECT EXTENTS SOIL GROUP AND LAND USE
NUMERICAL MODELING PRECIPITATION
0
1
2
3
4
5
6
7
8
January February March April May June July August September October November December
Ave
rage
Mo
nth
ly P
reci
pit
atio
n (i
n/m
ont
h)
Average Precipitation per Month
Abita Springs, LA Monthy Precipitation (in)
Covington, LA Monthy Precipitation (in)
Slidell, LA Monthy Precipitation (in)
Statistical Averages: • Wet Days = 109 days/year • Dry Days = 251 days/year • Daily = 0.2 in/day • Monthly = 5.2 in/month • Yearly = 62.7 in/yr • Longest Drought = 51 days • Longest Wet Period = 15 days
Common period of 1973 to 2010
NUMERICAL MODELING MIKE FLOOD
NUMERICAL MODELING EXISTING CONDITIONS
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
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
NUMERICAL MODELING TOPOGRAPHY/CANOPY CHANGES
• Scores Evaluated:
• Roadways Constructued on Undeveloped Land • Roadways Constructued on Existing Roadways and Abandoned
Railways
NUMERICAL MODELING DIRECT WETLAND IMPACTS
• Wetlands Delineated by Tetra-Tech within 250 ft Right-of-Way
• Scores Evaluated:
• Wetland Acres within Right-of-Way
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
NUMERICAL MODELING PONDING/DROUGHT VARIATIONS (7-DAY)
Ponding:
Drought:
NUMERICAL MODELING PONDING VARIATIONS (7-DAY)
NUMERICAL MODELING DROUGHT VARIATIONS (7-DAY)
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
NUMERICAL MODELING WATER LEVEL FLUCTUATIONS (2-YEAR STORM EVENT)
NUMERICAL MODELING ALIGNMENT COMPARISON
NUMERICAL MODELING ALIGNMENT COMPARISON
1 2 3 4
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
Experience │ Innovation │ Results
WATER RESOURCES Hydraulic & Hydrologic Engineering
337.237.2200
www.fenstermaker.com