Community Risk Assessment: How to Find Out What Hazards Your County Actually Faces

Most people guess at their local risk. They remember the flood that hit in 2011, they have heard the tornado siren, and they assume that is the list. A real community risk assessment works the other way around. It starts with the documents your county, your state and several federal agencies have already written about your exact location, then checks them against what has actually hit the ground near you. That record exists whether you read it or not, and none of it costs anything.

I covered the household level in how to assess your home's disaster risk. This one moves up to the town, the county and the block.

What is a community risk assessment?

A structured look at which hazards can affect a defined area, how likely each is, and who would be hurt. Federal regulation spells the method out: under 44 CFR 201.6, a local hazard mitigation plan must describe "the type, location, and extent of all natural hazards that can affect the jurisdiction," plus past occurrences, future probability, the buildings and critical facilities inside hazard areas, and "an estimate of the potential dollar losses to vulnerable structures."

Where do you find your county's official hazard list?

In the county or multi-jurisdiction hazard mitigation plan. Nearly every US county that wants federal mitigation money has one, because the plan is the eligibility ticket, and it must be resubmitted for approval within 5 years to keep that funding. Colorado's state mitigation office notes the process takes about a year, so jurisdictions start 18 to 24 months before expiration, which is why you sometimes find a draft open for comment (Colorado DHSEM).

To get your copy, search "[your county] hazard mitigation plan" plus "pdf." Most sit on the county emergency management or regional planning site and run 200 to 600 pages. Failing that, call county emergency management, ask for the mitigation planner, and ask for the current plan plus its expiration date. If a new one is in development, ask when public comment opens: the regulation requires "an opportunity for the public to comment on the plan during the drafting stage and prior to plan approval," so that window is yours.

One honest limit: quality varies. Some plans are rigorous. Some are consultant boilerplate with your county's name dropped in. You will know which you have in ten minutes.

What does the hazard ranking table tell you?

It tells you how your own emergency managers rated each threat, which beats any national average. Find the table in the risk assessment chapter scoring every hazard the plan profiles.

The University of Washington's planning guide describes the usual approach: a Priority Risk Index style method to quantify vulnerability, supported by maps of where each hazard hits, tables of occurrence history and damage estimates across scenarios (UW Institute for Hazard Mitigation Planning and Research). In practice the table scores four things per hazard:

• Probability. Highly likely, likely, possible or unlikely, sometimes with a recurrence interval.

• Magnitude. Negligible through catastrophic.

• Extent. One creek bottom, or the whole county at once.

• Warning time. Minutes for a tornado, days for a river flood, weeks for a drought.

Here is the part most guides skip. Read the bottom of the table, not just the top. The highest-ranked hazard is the obvious one you already think about. The surprise sits mid-table: the dam failure scenario, the hazardous materials corridor along the rail line, the heat profile added in the last update. Nobody near you is ready for those, because they do not feel local.

What does the local Emergency Operations Plan tell you?

Who does what during a disaster, and where shelters, evacuation and warning live. The mitigation plan reduces risk beforehand; the Emergency Operations Plan, or EOP, runs the response.

Most county EOPs come as a base plan plus annexes. Larimer County, Colorado is a clean example: its base plan covers authorities, concept of operations and assignment of responsibilities, and lists 17 Emergency Support Functions, including Mass Care, which names the American Red Cross as lead agency for shelters and carries sub-functions for housing and pets. Evacuation sits in its own Evacuation and Re-Entry Annex (Larimer County EOP).

The base plan is public and thin; the annexes carry the detail, and some are not posted. So ask emergency management four things:

• Which annex covers evacuation, and is there a zone map for my address?

• Which facilities are designated shelters for my area, and which take pets?

• How does the county issue warnings, and what do I sign up for?

• Is there a plan for residents who cannot self-evacuate, and how do they get on that list?

That last one matters more than people expect. If someone at home depends on oxygen, dialysis or a powered wheelchair, the answer shapes everything else. Once you have the zone and the routes, write them down the way we lay out in the family evacuation plan guide.

What is a THIRA, and why should you care?

A THIRA is a Threat and Hazard Identification and Risk Assessment: what your state and major urban areas run to decide which capabilities to build. Georgia's emergency management agency describes it as three steps answering what threats affect us, what impacts they would have, and what capabilities we should build, across prevention, protection, mitigation, response and recovery. Paired with it is the Stakeholder Preparedness Review, a self-assessment grading current capability against those targets, which GEMA says "aids jurisdictions in identifying preparedness capability gaps and sustainment requirements" (GEMA).

Why you should care: the SPR is where officials write down what they cannot do yet, a direct read on how much you need to cover yourself. If the gap list says mass care capacity falls short of target, your family plan should not assume a shelter cot. Full submissions are often not public, but many counties fold a THIRA summary into the EOP, and asking the coordinator "what came out of your last SPR" sometimes gets a straight answer.

Which public hazard maps should you check?

The ones matching your actual hazards. Check what has already happened before you check what might.

• National Risk Index. A relative risk score covering 18 natural hazards for every US county and census tract, built from expected annual loss (exposure, frequency, historic loss) combined with social vulnerability and community resilience (NIDIS). A one-screen snapshot.

• Flood maps. Learn the vocabulary first. A Special Flood Hazard Area is land covered by the base flood, the flood with a 1 percent chance of being equaled or exceeded in any given year. Zone A is that area mapped by approximate methods with no base flood elevation; Zone AE has engineered elevations. Shaded Zone X is the 0.2 percent annual chance area (Penn State Flood Risk). Your county GIS or floodplain administrator can show you your parcel.

• NOAA NCEI Storm Events Database. The "what has actually hit us" tool: severe weather records intense enough to cause death, injury or significant property damage, covering January 1950 through May 2026, searchable by county, date and event type across 48 event types (NCEI). Pull 20 years and the pattern shows up fast.

• USGS earthquake and landslide maps. The National Seismic Hazard Model turns earthquake sources, active faulting and ground shaking into the maps behind building codes and insurance rates, updated for all 50 states in 2023 (USGS). The US Landslide Inventory and Susceptibility Map holds 613,724 landslide locations at 90-meter resolution.

• Dams, levees and wildfire. The Army Corps National Levee Database documents 6,066 levee systems, about 22,000 miles of levee and 22 million people in leveed areas; the National Inventory of Dams is its companion. Downstream of either is a hazard your flood map may not show. State wildfire maps vary: California maps Fire Hazard Severity Zones in three classes, moderate, high and very high, effective April 1, 2024 in State Responsibility Areas, with an address lookup (CAL FIRE OSFM).

How do you find out what chemicals are stored near you?

You ask in writing, and the law says they have to tell you. It is the most overlooked piece of a community risk assessment, and it covers the hazard most likely to force a sudden evacuation.

The Emergency Planning and Community Right-to-Know Act set the structure. State Emergency Response Commissions coordinate statewide; Local Emergency Planning Committees "prepare chemical emergency response plans and review plans at least annually." Facilities send safety data sheets and Tier II inventory forms to their SERC, LEPC and local fire department, and EPA states those bodies "are required to make these reports available to the public" (EPA).

North Carolina's procedure shows what a request looks like: in writing, naming a specific facility, with a response on Section 312 Tier I and Tier II forms within 45 days. Facilities file those by March 1 each year, and for a facility holding under 10,000 pounds of a chemical the requester must include a statement of general need (NC Emergency Management). Your state differs, so ask your SERC. Two more: the Toxics Release Inventory tracks 810 listed chemicals and 34 chemical categories, and facilities using extremely hazardous substances file a risk management plan every 5 years under Clean Air Act section 112(r), with certain information public on request.

Who in your neighborhood will need help first?

The people whose vulnerability is already measured. The CDC and ATSDR Social Vulnerability Index is a place-based index and mapping application built from 16 US Census variables grouped into 4 themes, published at census tract level, and planners use it to size personnel needs and shape evacuation strategy (CDC/ATSDR).

Pull your tract and read the theme scores, not just the overall rank. A tract can sit at average overall while scoring very high on household characteristics, which usually means older adults, young children or people with disabilities. That is a staffing problem for the county and a doorbell list for you. Then walk it: no index knows which house has a neighbor on home oxygen or which driveway floods first. That is the work in building a neighborhood emergency plan, and the data just tells you where to start knocking.

What is the 6-step community risk assessment procedure?

A few hours over two weeks, and you will know more about local risk than anyone else on your street.

1. Get the plan, read one chapter. Search "[your county] hazard mitigation plan pdf," or ask the county mitigation planner. Open the risk assessment chapter and write down the ranking table's top 5 plus anything mid-table that surprises you.

2. Check what has actually hit. In the NCEI Storm Events Database, set state, county and a 20-year range, leave event type blank. Count events by type and compare to the plan's ranking. Where they disagree, ask why.

3. Map your parcel against each top hazard. Run the National Risk Index for your county and tract, then the specific maps: county GIS for your flood zone, your state wildfire map, USGS for seismic and landslide, the levee and dam inventories if you sit downstream.

4. Find out what is stored nearby. Look up your area in TRI, then write your Local Emergency Planning Committee for its Tier II request procedure and the reporting facilities in your zip code. Your SERC or county emergency management will tell you who your LEPC is.

5. Get the response side. Call county emergency management, ask the four EOP questions above, and sign up for alerts on the call. Pull your tract's SVI theme scores too.

6. Write one page and share it. Top 3 hazards, the trigger for each, what your household does, what your block does, who checks on whom. Hand it to the neighbors who would use it.

How do you turn the findings into a plan?

By cutting hard. A 400-page county plan is not a household plan, and 18 hazards is not actionable. For each of your top 3, write four lines: the trigger, the decision (shelter in place or leave), the route or the room, and the one supply gap to close this month. Then add the block layer: a neighbor or two who know your plan, know who needs a check, and know the meeting spot. That is the difference between an assessment in a folder and one that changes what happens on a bad night.

Frequently asked questions

Is my county's hazard mitigation plan public?

Yes, in almost every case. Regulation requires a public comment opportunity during drafting and before approval, and the adopted plan is normally posted on the county emergency management or regional planning site. If not, call the mitigation planner.

How often is a community risk assessment updated?

On a 5-year cycle. A jurisdiction must resubmit its plan for approval within 5 years to stay eligible for mitigation project grant funding, and plan maintenance must include monitoring and evaluation within that cycle.

What is the difference between a hazard mitigation plan and an emergency operations plan?

The mitigation plan reduces risk before anything happens, so it carries the hazard ranking and loss estimates. The emergency operations plan runs the response, carrying the emergency support functions and the annexes for evacuation, warning and mass care.

How do I find out what hazardous chemicals are stored near my house?

Ask your Local Emergency Planning Committee in writing, naming the facility. Facilities file Tier II inventories by March 1 each year, and SERCs and LEPCs must make those reports public. North Carolina answers Section 312 requests within 45 days.

Do I need GIS skills or special software to do this?

No. Every tool named here is a public web page with a search box, and the plans are PDFs. The University of Washington's guide says assessments should be relevant, in progress and accurate, without sophisticated technology.

The numbers, in one place

You never know, but you can always be ready.

Sources: 44 CFR 201.6, Local Mitigation Plans (Cornell LII) | Colorado DHSEM, Regional and Local Hazard Mitigation Plans | University of Washington, Local Hazard Mitigation Planning Web Guide, Task 5 | Larimer County, Colorado Base Emergency Operations Plan | Georgia Emergency Management and Homeland Security Agency, THIRA | NIDIS, National Risk Index for Natural Hazards | NOAA NCEI Storm Events Database | NOAA NCEI Storm Data Export Format | Penn State Pennsylvania Flood Risk Glossary | USGS National Seismic Hazard Model | USGS US Landslide Inventory and Susceptibility Map | USACE National Levee Database | CAL FIRE Office of the State Fire Marshal, Fire Hazard Severity Zones | EPA, What is EPCRA | EPA, What is the Toxics Release Inventory | EPA, Risk Management Program | North Carolina Emergency Management, Procedures for Obtaining Hazardous Chemical Information | CDC/ATSDR Social Vulnerability Index