fema region iii storm surge project
DESCRIPTION
FEMA Region III Storm Surge Project. Return Level Results and Historical Comparison. FEMA Region III Coastal Workshop USACE- Field Research Facility November 1, 2011. Michael Forte USACE-ERDC. Advancements. 2010 Finite Grid 30-40m Minimum Resolution. 1978 Triangular Finite Grid - PowerPoint PPT PresentationTRANSCRIPT
US Army Engineer Research and Development Center
FEMA Region III Storm Surge Project
Return Level Results and Historical Comparison
Michael ForteUSACE-ERDC
FEMA Region III Coastal Workshop
USACE- Field Research FacilityNovember 1, 2011
US Army Engineer Research and Development Center
1978 Triangular Finite Grid5-10km resolution
2010 Finite Grid30-40m Minimum Resolution
Advancements
FEMA Tropical & Extratropical 100yr Return Levels
• Delaware Bay, Eastern Shore of VAand Southern Chesapeake Bay (Norfolk & Tidewater VA)contain the highest surge levelsthroughout Region III.
• Lowest return levels at Middle Chesapeake Bay
All UNITS ARE IN US FEET
100Yr Historical Return LevelsStill Water Elevation (SWEL)
Compiled by Dewberry from multiple Flood Insurance Studies throughoutRegion III
Sources:
USACE – Potomac (DC area)VIMS – Majority of Chesapeake Bay NWS- Hydro (Gauge analysis)USGS – (WL Gauge analysis)Grenier Engineering (WLGauge analysis)
Compare existing/historical with RegionIII 100yr results
100Yr SWEL ComparisonFEMA R3 minus Historical
•Majority of values +/- 1 foot when Compared to Historical Study
•Elevated Return Levels in Delaware Bay and Lower Chesapeake (Norfolk) (+ 1.5 – 3.5 ft)
•Decreased Return Levels in upperChesapeake Bay and VA Eastern Shore(- 1.5 – 3.5ft)
• Overall good agreement with a couple of important differences
US Army Engineer Research and Development Center
SWEL Comparison
Scatter Plot of Region III and Historical SWEL values
Why the changes?
• Storm track• Historical gauge analysis
• Historical Studies for Delaware Baywere based on gauge analysis with very few to no tropical systems occurring.
• Tropical Storm tracks –winds drive water South down the Chesapeake Bay
• Delaware Bay acts as a catch basinwith few tributaries allowing waterto pile up.
Why the changes?
• Storm track• Historical gauge analysis
• Historical Studies for Delaware Baywere based on gauge analysis with very few to no tropical systems occurring.
• Tropical Storm tracks –winds drive water South down the Chesapeake Bay
• Delaware Bay acts as a catch basinwith few tributaries allowing waterto pile up.
Why the changes?
• Storm track• Historical gauge analysis
• Historical Studies for Delaware Baywere based on gauge analysis with very few to no tropical systems occurring.
• Tropical Storm tracks –winds drive water South down the Chesapeake Bay
• Delaware Bay acts as a catch basinwith few tributaries allowing waterto pile up.
Region II & Region III100Yr Level Comparison
Region II Modeled output compared With Region III
Region II 100YrModeled Output
Region II & Region III100Yr Level Comparison
Another Encouraging Result!
• Majority of points are within +/- 1 foot.
• Two modeled outputs from twodifferent teams, run on two different computers = VERY GOODAGREEMENT
Region III minus Region II Histogram
US Army Engineer Research and Development Center
FEMA Region III Storm Surge Project
Summary/Conclusions
• Excellent agreement with historical SWELS with a few important differences
• Region II Compares well with Region III