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
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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
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US Army Engineer Research and Development Center
1978 Triangular Finite Grid5-10km resolution
2010 Finite Grid30-40m Minimum Resolution
Advancements
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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
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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
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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
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US Army Engineer Research and Development Center
SWEL Comparison
Scatter Plot of Region III and Historical SWEL values
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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.
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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.
![Page 9: FEMA Region III Storm Surge Project](https://reader036.vdocuments.us/reader036/viewer/2022062520/56816262550346895dd2c2d9/html5/thumbnails/9.jpg)
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.
![Page 10: FEMA Region III Storm Surge Project](https://reader036.vdocuments.us/reader036/viewer/2022062520/56816262550346895dd2c2d9/html5/thumbnails/10.jpg)
Region II & Region III100Yr Level Comparison
Region II Modeled output compared With Region III
Region II 100YrModeled Output
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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
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Region III minus Region II Histogram
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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