Allegheny County, PA flood risk and hazards

Allegheny County in the state and national rankings

Allegheny County has about $354.2 million in modeled expected annual loss, ranking #58 of 3,232 nationally. Its share of Pennsylvania modeled loss is 8.7%, with a state rank of #2 of 67. FEMA’s about $354.2 million figure describes a long-run average; actual annual loss can differ. The next higher national total is about $354.7 million, in Denton County, TX. Sacramento County, CA ranks immediately below it, with about $352.4 million in modeled annual loss. At about $667.1 million, Philadelphia County, PA is one place higher in the state loss ordering. Its 16.4% state loss share accompanies an estimate about $312.8 million away from this county’s total. At about $296.7 million, Montgomery County, PA is one place lower in the state loss ordering. About $57.6 million separates those two estimates, and the other county’s state loss share is 7.3%.

Pennsylvania county comparisons

Allegheny County hazard estimates

Riverine Flood

FEMA models about $295.0 million in expected annual loss from riverine flooding, placing the county #20 of 3,232 nationally. In Pennsylvania, this estimate ranks #1 of 67 and represents 83.3% of the county’s modeled loss; FEMA assigns a Very High rating; the same rating for riverine flooding covers 2 Pennsylvania counties and 26 across the US.

Cold Wave

FEMA models about $31.9 million in expected annual loss from cold waves, placing the county #32 of 3,232 nationally. At 9.0% of the county’s modeled loss, the hazard places #2 of 67 statewide; FEMA assigns a Very High rating, matching 39 US counties, including 3 in Pennsylvania, for this hazard.

Tornado

The national loss rank for tornadoes is #268 of 3,225, based on about $8.4 million in modeled expected annual loss. At 2.4% of the county’s modeled loss, the hazard places #6 of 67 statewide; FEMA assigns a Relatively High rating; for tornadoes, 6 state counties and 272 US counties share that label.

Heat Wave

With about $5.4 million in modeled expected annual loss from heat waves, the county ranks #184 of 3,202 in the national comparison. This hazard makes up 1.5% of the total; FEMA assigns a Relatively Moderate rating, and its loss ranks #7 of 67 in Pennsylvania; the same rating for heat waves covers 13 Pennsylvania counties and 551 across the US.

Earthquake

For earthquakes, about $4.0 million in expected annual loss puts the county #426 of 3,232 across the US. At 1.1% of the county’s modeled loss, the hazard places #10 of 67 statewide; FEMA assigns a Relatively Low rating; the Relatively Low label covers 19 state counties and 962 nationally for earthquakes.

Strong Wind

With about $3.8 million in modeled expected annual loss from strong wind, the county ranks #117 of 3,225 in the national comparison. Its 1.1% share of total loss comes with a state loss rank of #5 of 67; FEMA assigns a Relatively High rating; the Relatively High label covers 19 state counties and 442 nationally for strong wind.

About $263.1 million separates riverine flooding from cold waves in the local estimates, equivalent to 74.3 percentage points of county loss. The loss estimate for cold waves exceeds tornadoes by about $23.6 million, equivalent to 6.7 percentage points of total loss. Between tornadoes and heat waves, the modeled dollar gap is about $3.0 million; their shares differ by 0.8 percentage points. About $1.4 million separates heat waves from earthquakes in the local estimates, equivalent to 0.4 percentage points of county loss. For earthquakes, modeled loss is about $242,000 above strong wind, leaving 0.1 percentage points between their county shares.

Population and recorded values

Allegheny County covers about 752 square miles, with 1,249,907 residents in FEMA data. FEMA lists about $294.36 billion in building value. The recorded agricultural value is about $17.7 million. Per resident, the modeled annual amount is about $283; the Pennsylvania average is about $313. Its 9.6% share of state residents sits alongside 8.7% of of annual loss. The county contains 9.7% of the building value recorded across Pennsylvania. Among 67 state county records with both inputs, its density stands at position 4 from highest to lowest. Those recorded totals give about 1,663 residents per square mile, versus about 279 across Pennsylvania. The median county population in Pennsylvania is about 83,927, compared with 1,249,907 locally. Of FEMA’s US population, 0.4% lives here, alongside 0.2% of national modeled annual loss. Per-person modeled loss is about $283 locally; the corresponding US average comes to about $459. About $348.5 million of annual loss falls within the six leading hazards, accounting for 98.4% of the total. The balance outside those six estimates is about $5.7 million, or 1.6% of total loss. About $2.0 million places ice storms at number 7 in the local loss list and #2 of 67 within Pennsylvania. With 0.6% of county loss, this hazard has national placement #89 of 3,001. The county’s number 8 hazard by dollar loss is lightning: about $1.7 million, with a state rank of #10 of 67. Its national loss rank is #195 of 3,222, and it represents 0.5% of the county’s modeled loss.

FEMA labels and risk score

Allegheny County has a FEMA risk index score of about 98.1, ranking #61 of 3,144 nationally. Among 67 Pennsylvania counties, 4 receive the same Relatively High label for risk index. Among 67 Pennsylvania counties, 4 receive the same Relatively High label for expected annual loss. For social vulnerability, FEMA assigns Relatively Low; 20 counties in Pennsylvania have that label. FEMA labels community resilience as Very High, matching 27 county records across Pennsylvania. Within Pennsylvania, the risk score places #2 of 67 and the dollar loss places #2 of 67. This combination, Relatively Low for vulnerability and Very High for resilience, occurs in 11 counties in Pennsylvania. Those counties together hold 23.5% of Pennsylvania modeled loss, including this county’s 37.0% share of their total. The adjacent state score above this county belongs to Philadelphia County, PA: about 99.6, ranked #1 of 67. Its share of statewide modeled loss is 16.4%; FEMA’s risk index label there is Very High. On the state risk-score list, Montgomery County, PA sits immediately below, scoring about 96.8 and ranking #3 of 67. Its share of statewide modeled loss is 7.3%; FEMA’s risk index label there is Relatively High. Nationally, 632 counties carry the same Relatively Low social vulnerability label, covering 30.0% of FEMA’s recorded population. Nationally, 629 counties carry the same Very High community resilience label, covering 27.2% of FEMA’s recorded population. The county’s Very High group contains 3 hazards: cold waves, ice storms, riverine flooding. The county’s Relatively High group contains 4 hazards: lightning, strong wind, tornadoes, winter weather. The local Relatively Moderate hazard group contains 1 entries: heat waves. The county’s Relatively Low group contains 3 hazards: earthquakes, hurricanes, landslides. Across the county’s hazard ratings, 3 carry Very Low: avalanches, hail, wildfires.