FEMA risk index: county vs census tract

Which questions can county records answer?

County records summarize hazard categories, annualized dollar loss and recorded exposure for the named county. It gives a consistent area unit for comparing markets and organizing a shortlist. Attach the source county identifier to the finding so another reviewer can see precisely which geography supplied the evidence.

For a portfolio team, county context can reveal where operating locations share an area record. That is useful for planning follow-up research and discussing concentration. It is also useful when a facility register contains addresses but the immediate task is to identify which county evidence is available. Record the verified county identifier alongside the facility name so the geographic match can be reviewed.

This sample holds county records only; tract records are a separate FEMA release. The table is a county example, not a county-to-tract comparison. It deliberately retains each county's identifier and separates hazard labels from annualized loss. These values describe the named areas. They can frame a research question about locations inside those areas without answering it on behalf of every location.

Which details require evidence within the county?

County grain does not reveal the variation within a county. A shared flood rating does not locate a flood boundary, describe a building's elevation or identify the route used to reach a facility. A county wildfire label does not inspect roofing, vegetation management or the condition of nearby infrastructure. These are different questions with different evidence needs.

A county total also cannot tell you the loss attributable to the assets on your register. The county includes exposure beyond the locations your team supplied. Do not describe an area total as portfolio expected loss or divide it across your facilities to manufacture asset estimates. Keep your own asset valuations and coverage records in clearly separate fields.

Non-rating statuses do not solve the scale problem. If a county field says No Rating or Not Applicable, preserve the label and record the documentation check needed to interpret it. Moving to a smaller geography is not a reason to replace an unresolved source status with an assumed category.

When do I need tract or parcel evidence?

Consider tract evidence when the research question concerns variation between communities within a county. FEMA publishes the index at census tract level too. Start with FEMA and inspect its source documentation before choosing a tract extract. This guide has not loaded or validated tract values, so it does not present tract comparisons as completed work.

Consider parcel or building evidence when the decision concerns a specific site. A property flood-zone question needs official map evidence tied to the location. Building condition, elevation and operational vulnerability call for their own records and qualified review where appropriate. A smaller statistical area still represents an area; it is not a building inspection.

Write the decision question before choosing the geographic unit. If the task is market comparison, county evidence may be a practical starting point. If the task is a facility mitigation decision, record what site evidence is needed and who will obtain it. Choose the source because it answers the question, rather than assuming the smallest available unit is automatically sufficient.

How do I match a facility without hiding uncertainty?

Retain the supplied address, stable facility ID and verified geographic match as separate items. Preserve county identifiers as text to keep leading zeros. If coordinates are unavailable or unverified, say so. A formatted address does not prove that a geographic match has been checked, particularly near boundaries or where the supplied location description is incomplete.

Record the matching method, verification date, and reviewer with the joined record. When a facility appears close to a boundary, record the uncertainty and the evidence needed to resolve it. Do not choose the neighboring county whose rating looks more plausible. The location match should be established independently of the desired interpretation.

If later research adds tract evidence, retain the tract identifier beside the county identifier rather than replacing it. Keep the source release and geographic unit on each evidence row. This preserves the distinction between the area originally screened and the smaller area subsequently investigated, allowing a reviewer to understand how the evidence developed.

Can I compare or combine different geographic levels?

Compare like geography with like geography when explaining relative categories. A tract and a county are different comparison units. Do not interpret a difference between their labels as a measured change in risk at a facility. First inspect the source definitions, release and geographic coverage, then explain what each record describes.

Do not assume that averaging tract categories recreates a county category. Category words are not additive measures. Nor should a county total be added to smaller-area totals describing overlapping exposure. An apparently simple spreadsheet aggregation can count the same geography repeatedly or combine values whose definitions differ.

For a mixed evidence register, group the outputs by purpose. Keep county screening context, tract research and property map findings as distinct evidence types linked by the facility ID. Use a note to explain why more detailed evidence was requested. The reader should be able to tell which conclusion came from which source and geographic unit.

What should the next reviewer receive?

Give the reviewer the register, geographic identifiers, source fields and match evidence. Include unresolved rows and explain whether blanks reflect unknown locations, unreviewed coverage or missing source values.

Carry forward the question that triggered finer research. A request to check a flood boundary is more actionable than a generic instruction to assess risk. Name the owner, the source to inspect and the decision waiting on that evidence. When a correction arrives, preserve the original match and reason for the change so the revised output remains traceable.

Which decisions require additional evidence?

The county example cannot measure variation among census tracts because this sample contains no tract records. Before adding a separate tract release, check identifiers, boundaries and field definitions. Retain both geographic units in the register so a later reviewer can distinguish county screening from smaller-area research. A finer unit still needs evidence appropriate to the decision.

How should I cite the evidence and review date?

Last reviewed: 2026-10-23. Source: FEMA, FEMA National Risk Index. The county sample supplies the worked values. Keep the release and field notes from the methodology with exported figures. The review date records when this guide was reviewed; the underlying observations have their own periods.