Data, Maps and Risk: How Good is Good? Tropical Storm Nicole Case Study Kenneth Ashe, P.E., CFM North Carolina Floodplain Mapping Program

windsor

Town of Windsor, Bertie County 20,000 people Coastal plain Roanoke & cashie river

About 2.5 square miles Just under 2300 people Bertie county seat since 1774 Sits on the original 100 acres of the original town

Founded in early 1700s Agricultural history King Bazemore House dates to 1763 Access to Cashie River and streams Rich wetlands Quaint eastern nc charm Livermoor Park and Mini petting zoo River Center Heritage Center

Tropical Storm nicole

Late September 2010 A deep, stationary trough of low pressure parked over the Ohio and Tennessee valleys west of the Appalachians drew a steady stream of tropical moisture, including the remnants of Tropical Storm Nicole, up the East Coast. The results were heavy rain and flooding from Florida to the coastal Carolinas up into the Chesapeake Bay region and NASA's TRMM satellite captured rainfall from the event. In the U.S., highest rainfall occurred over coastal North Carolina where up to ~20 inches, shown in dark brown) fell. Almost all of eastern N.C. received at least 8 to 10 inches of rain (shown in bright green and yellow). From northern Fla. to central Penn. at least 4 inches (shown in darker blue) of rain fell with several areas in excess of ~6 to 8 inches (shown in dark and bright green, respectively). Locally, upwards of just over 20 inches in parts of N.C. Credit: NASA/SSAI, Hal Pierce `

NCC015-012214- /O.EXT.KAKQ.FL.W.0028.000000T0000Z-101004T0000Z/ /WNDN7.3.ER.100930T1238Z.101001T0630Z.101003T1800Z.NR/ 614 AM EDT FRI OCT 1 2010 ...FLOOD WARNING EXTENDED UNTIL SUNDAY EVENING...THE FLOOD WARNING CONTINUES FOR THE CASHIE RIVER NEAR WINDSOR * UNTIL SUNDAY EVENING...OR UNTIL THE WARNING IS CANCELLED. * AT 05:16 AM FRIDAY THE STAGE WAS 15.3 FEET * FLOOD STAGE IS 8.0 FEET * FORECAST...THE RIVER WILL CONTINUE RISING TO NEAR 15.9 FEET BY THIS AFTERNOON. THE RIVER WILL FALL BELOW FLOOD STAGE SUNDAY EARLY AFTERNOON. * AT 15.0 FEET...ROUTE 13...ROUTE 17...AND HOGGARD MILL ROAD INNUNDATED.

Extent of flooding and floodplain mapping

Risk & expected damages

IHRM Vision Hazard Data 1. Hazard Identification 4. Communication 2. Vulnerable Systems Built Environment Data, Critical Infrastructure, Socio-Economic Variables First Floor Elevations 3. Risk Assessment 5. Mitigation 4. Communication

Hazard Identification River Flooding (WSEL & Depth Rasters, 3D TINs) Gold Level: 10%, 4%, 2%, 1%, 0.2%, annual chance recurrence intervals 1% annual chance future conditions with 10%, 20% and 35% imperviousness build-out scenarios Percent Annual Chance & 15 and 30 Year Probability Rasters Silver Level: 10%, 2%, 1%, and 0.2% annual chance recurrence intervals Bronze Level:

Gold Level Flooding Data This is the 1% annual chance depth raster with the vector delineated floodway.

Vulnerability Data Collection Final Building Footprint Database 5.1 Million Buildings Completed January 2011 Metadata documenting image source and date Distributed countywide datasets to all Counties John

Vulnerability Data Collection FFE Database FFE Data Collected for: 4 IHRM Counties 19 Coastal Counties 7 Map Maintenance Counties Total: 150,000 Buildings RMSE accuracy of 0.3 feet 100YR Flood Elevation = 13 ft. FFE = 5.2 ft.

Field Collection First Floor Elevation Foundation Type Roof Shape Roof Slope Number of Stories Parcel Conflation Occupancy Type Building Value Year Built Heated Sq Ft HAZUS Block De-Conflation Roof Cover Type Roof Cover Quality Water Resistance Roof Deck Attachment Roof Deck Age Roof Wall Connection Roof Frame Type Hurricane Shutters Roof Tie Downs Window Area Masonry Reinforcing Joist Spacing Number of Units

HAZUS Model Building Type - HU Attributes available from Census Block geometry HAZUS Hurricane Building Scheme Building Type Occupancy Type Number of Stories Southeast Inland WOOD RES1 1 Model Building Types Lookup Table Model Type Lookup Description WSF1 Single Family Homes, 1 Story - Wood Attributes for Model Building Type Attribute Field Highest Percentage Attribute Value Roof Shape 95% Gable 5% Hip Secondary Water Resistance 100% No 0% Yes Roof Deck Attachment 44% 6d @ 6"/12" 34% 8d @ 6"/12" 6/8d Mix @ 6"/6" 22% 8d @ 6"/6" Roof-Wall Connection 63% Strap 37% Toe-nail Shutters For example, From the block geometry if we knew that a structure was OCCUP RES1, Building Type Wood and 1 story we then go to our secondary Model building type lookup table that would in turn filter into the building characteristics distributions table for tertiary attribute assignments.

Town of Windsor HAZUS Estimates TS Nicole 30 Buildings Damaged Total Damage Building $3.35 million Contents $5.57 million Total $9.18 million Residential Only Damage Building $2.3 million Contents $1.52 Million Total $3.82 Million

IHRM Estimates TS Nicole 97 Damaged Buildings Building and Contents Damage = $475,706

FEMA Assistance HA includes: Flood Damages: Building Damage Contents Damage Rental Assistance Flood Damages: 140 @ $566,101 Damage only 63 Buildings $463,000 - $472,000

Comparison TS Nicole Flooding (100-year flood discharge) HAZUS IHRM Buildings 30 Damage $9,180,00 IHRM Buildings 97 Damage $476,000 FEMA Payments Buildings 63 - 140 Damage $463,000 - $566,000

IHRM Pilot Study IHRM Pilot County Edgecombe – 100-year Estimated Direct Damages HAZUS – ~$100 million IHRM – ~$12 million

Risk MAP Early Demonstration AAL (structure and structure contents losses ) Nash HAZUS – $31,095,111 IHRM – $ 2,923,246 Pitt HAZUS – $15,740,508 IHRM – $ 769,706 Scotland HAZUS – $1,153,890.16 IHRM – $ 86,654.31 AAL Based on: 10% Annual Chance (10-yr) 4% Annual Chance (25-yr) 2% Annual Chance (50-yr) 1% Annual Chance (100-yr) 0.2% Annual Chance (500-yr)

Notes Not all Assistance is Equal Actual Building Location Matters Building Elevation Matters Correct Depth Damage Curve Matters Database Driven Matters

QUESTIONS