Wake County Hazard Mitigation Plan - January 2020

ANNEX A: WAKE COUNTY UNINCORPORATED AREAS

A.3.2 Flood Table A.12 details the acreage of unincorporated Wake County’s total area by flood zone on the effective DFIRM. Per this assessment, over 10 percent of the unincorporated area in the County falls within the mapped 1%-annual-chance floodplains. Table A.12 – Flood Zone Acreage in Unincorporated Wake County

Flood Zone

Acreage

Percent of Total (%)

Zone A Zone AE

244.34

0.07

34,276.21 1,923.22 302,007.04 338,450.81

10.13

Zone X (500-year) Zone X Unshaded

0.57

89.23

Total

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Source: FEMA Effective DFIRM; Wake County GIS

Figure A.4 reflects the effective mapped flood hazard zones for Wake County, and Figure A.5 displays the depth of flooding estimated to occur in these areas during the 1%-annual-chance flood. To supplement the IRISK assessment of property at risk from the 1% annual chance flood event in Section 4 and provide a clearer picture of the current property at risk in Unincorporated Wake County, current parcel data was evaluated to identify parcels developed since 2010. Using GIS analysis, parcels developed after 2010 were compared to the boundaries of the 1% annual chance floodplain to identify the exposure of newly developed property to the base flood. In most cases, a parcel was considered exposed to the floodplain if any portion of the parcel was located in the floodplain. This assessment does not evaluate flood impacts or provide damage estimates. However, this summary of development in or near the floodplain since 2010 provides some context to understand the degree to which the IRISK exposure and vulnerability numbers differ from current conditions. Table A.13 provides a summary by land class of parcel development located in the 1% annual chance floodplain from January 2011 to April 2019. Table A.13 – Parcels Developed 2011 or Later and Located in 1% Annual Chance Floodplain

Land Class

Number of Parcels

Sum of Building Value

Acres Greater Than 10 With House

20

$9,213,446

Forestry Industrial

1 1

$777,207

$48,366,843 $46,029,733 $104,387,229

Residential Less Than 10 Acres

118 140

Grand Total

Source: Wake County Open Data; retrieved April 8, 2019; FEMA Effective DFIRM

Table A.14 provides building counts and estimated damages for Critical Infrastructure and Key Resources (CIKR) buildings by sector and flood event in the City of Raleigh. Table A.14 – Critical Facilities Exposed to Flooding, Unincorporated Wake County

Sector

Event

Number of Buildings at Risk

Estimated Damages

100 Year Floodway 100 Year 100 Year Floodway 100 Year Floodway

20

$439,223 $23,765 $86,000 $60,845 $60,845 $586,068 $84,610

Commercial Facilities

1 2 1 1

Government Facilities

Transportation Systems

23

All Categories

2

Wake County Multi-Jurisdictional Hazard Mitigation Plan 2019

294

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