Municipal Risk Assessment — Oiriunu
For Municipalities Risk Assessment
Municipal assessment tool

Community-scale flood risk in under 5 minutes

Answer four sets of questions about your jurisdiction and we’ll generate a community risk score, vulnerability breakdown across drainage, zoning, and infrastructure, and a funding-aligned project recommendation list.

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Step 1 of 4

Jurisdiction details

Basic location and scale information. Used to look up relevant FEMA data, state programs, and regional risk patterns.

Land use and density

Development patterns directly affect runoff volumes and infrastructure loading. Select the options that best describe your jurisdiction’s dominant character.

Known flood zones and history

Prior flood events and FEMA zone distribution provide the strongest signal of community-scale risk. Select all that apply.

Zone AE (high-risk fluvial / riverine)
Zone VE (high-risk coastal / wave action)
Zone AO / AH (shallow flooding)
Zone X (moderate / minimal — FEMA-designated)
Significant unmapped / informal flood areas known locally

Infrastructure profile

Infrastructure age, type, and known condition significantly affect community flood vulnerability and project prioritisation.

Undersized culverts or pipes causing backflow
Failing or overtopped levees / berms
CSO overflows during storm events
Maintenance backlog — routine inspections delayed
No known significant infrastructure issues

Building your community risk report

Analysing jurisdiction profile…

Cross-referencing FEMA flood zone data
Analysing infrastructure vulnerability profile
Mapping drainage capacity gaps
Scoring zoning and development risk
Identifying priority project zones
Matching federal and state funding programs

Municipal flood risk report

Harris County, Texas · County · Population 4.8M

Based on your jurisdiction profile, FEMA zone data, and regional risk patterns. This report is a starting assessment — a full professional survey provides definitive findings.

Low Mod High
71
High Risk
Community score: 71 / 100

Risk factor breakdown

Drainage capacity
82
Zoning / land use exposure
68
Infrastructure condition
75
Flood zone exposure
70
Disaster declaration history
60
Existing protection measures
40

Vulnerability breakdown

Detailed findings across the three primary vulnerability categories — drainage, zoning, and infrastructure gaps. Use the tabs to navigate each domain.

Combined sewer overflow (CSO)

Critical

Combined sewer system regularly overflows during storm events exceeding 1-inch/hour rainfall. Overflow frequency has increased 40% over the past decade as storm intensity rises. Peak capacity reached at historically moderate events.

Overflow frequency18–24 events/yr
Estimated capacity deficit~35%
Infrastructure age52 years avg

Culvert undersizing

High

Approximately 34% of mapped culverts are sized for 10-year storm events. Updated precipitation data indicates these culverts now have effective return periods of 4–6 years, causing routine backflow into residential areas.

Undersized culverts~34% of inventory
Backflow-affected parcelsEst. 12,400
Replacement cost est.$28–$45M

Stormwater detention capacity

High

Existing detention basins were designed for a 1970s-era land use profile. Impervious surface has increased 28% since original basin sizing, reducing effective detention capacity per unit area across most watersheds.

Impervious surface increase+28% since design
Basins at or near capacity7 of 11 major basins
Additional capacity neededEst. 340 acre-feet

Green infrastructure coverage

Medium

Bioretention, permeable pavement, and urban tree canopy collectively intercept approximately 8% of stormwater volume — well below peer community benchmarks of 18–22%. Significant expansion opportunity in commercial and residential corridors.

Current GI coverage~8% of impervious area
Peer benchmark18–22%
Tree canopy cover14% (target: 25%)

In SFHA

23%

Of jurisdiction land area within FEMA Special Flood Hazard Area — well above national average of 8%. Includes significant residential and commercial development approved prior to current floodplain ordinance standards.

Development in floodplain

18%

Of SFHA is developed with permanent structures. Approximately 34,000 parcels face mandatory flood insurance requirements. An estimated 12,000 are non-compliant or under-insured based on NFIP participation data.

Flood buffer intact

61%

Of riparian corridors and wetland buffers remain undeveloped. This represents significant natural flood storage capacity that should be protected through conservation easement or zoning overlay to prevent future development pressure.

Zoning ordinance was last updated in 2009 — does not reflect current FEMA FIRM panels or updated precipitation data. A zoning ordinance review is recommended as a priority.
Three active subdivision approvals in Zone AE identified. Cumulative substantial improvement calculations should be reviewed before additional permits are issued in these areas.
Approximately 4,200 repetitive loss properties identified across 8 zip codes. These clusters represent priority acquisition or elevation targets for FMA grant applications.
28% of Zone X properties have modelled risk exceeding the Zone AE 1% annual chance threshold — indicating significant unmapped risk that may not be captured in current insurance requirements or community disclosure obligations.
System Key finding Condition Investment gap
Combined sewer system
52-year average age. Capacity designed for 1.5″/hr rainfall. Current 100-year events exceed 2.8″/hr in this region.
D+
$120–190M
Culvert network
34% undersized relative to current precipitation. 18% showing structural deterioration on last inspection cycle.
D
$28–45M
Levee / berm system
Primary levee protecting 3,400 parcels last certified in 2014. Inspection overdue. Subsidence detected in two segments.
C–
$14–22M
Detention basin network
11 major basins. 7 operating at or above design capacity. 3 require sediment removal. Spillway condition: fair.
C
$8–14M
Green infrastructure
8% of impervious area covered. Maintenance program underfunded. 40% of bioretention cells underperforming due to vegetation failure.
C+
$4–8M
Total estimated gap
Combined investment gap across all systems. Does not include soft costs (engineering, permitting, right-of-way).
D+
$174–279M

Recommended actions

Ranked by the combination of risk reduction impact, cost-effectiveness, and FEMA funding eligibility. Completing the top three actions would reduce the community risk score by an estimated 18–24 points.

1

CSO capacity upgrade — priority watersheds

Phase 1 combined sewer upgrade targeting the three highest-overflow watersheds. Adds 35% capacity buffer against current 100-year storm events. Eliminates routine overflow for storms up to 2-inch/hour intensity.

$38–52M
Critical impact

Phase project across 3 years to manage capital budget. Qualifies for BRIC and EPA Clean Water SRF. Engineering and environmental review: est. 14 months.

BRIC + EPA SRF eligible
2

Culvert replacement programme — priority 34%

Replace the 34% of undersized culverts in identified backflow zones, prioritised by number of affected parcels and proximity to repetitive loss clusters. Phase 1 targets top 80 culverts affecting est. 6,200 parcels.

$12–18M
Critical impact

Eligible under BRIC as a community-scale drainage project. Benefit-cost ratio estimated 4.2:1 based on repetitive loss data. Bundle with detention upgrades to strengthen application.

BRIC eligible
3

FMA repetitive loss cluster — acquisition and elevation

Target the 4,200 identified repetitive loss properties across 8 zip codes for structured FMA grant applications. Priority: severe repetitive loss properties (SRL) which qualify for 100% federal cost share — zero local match required.

Varies / grant-funded
Critical impact

FMA SRL properties require no local match. Begin with property owner outreach in highest-density SRL clusters. Floodplain manager to initiate sub-application in next FMA cycle.

FMA 100% federal (SRL)
4

Zoning ordinance update — align with current FIRM and precipitation data

Update floodplain ordinance to reflect current FEMA FIRM panels (2023), updated IDF curves, and best practices for cumulative substantial improvement tracking. Prevent future development that compounds the existing risk profile.

$180–360K
High impact

No capital outlay — planning and legal cost only. Prerequisite for maintaining NFIP participation and Community Rating System (CRS) credit points that reduce resident insurance premiums.

CRS credit eligible
5

Levee inspection and recertification

Commission engineering inspection and FEMA accreditation review for the primary levee protecting 3,400 parcels. Subsidence detected in two segments requires geotechnical investigation before next certification window.

$1.2–2.4M
High impact

Levee decertification triggers mandatory flood insurance for 3,400 parcels — significant resident cost burden. Inspection is lower cost than consequences of inaction. FEMA BRIC covers levee safety projects.

BRIC levee safety eligible

Funding alignment

Based on your jurisdiction profile, disaster declaration history, and project types, these federal and state programs are most likely to fund your priority projects — with estimated award ranges and key eligibility factors.

4
Applicable federal programs identified
$55M+
Estimated fundable project value (federal share)
75%
Max federal cost share (standard projects)
100%
Federal share for SRL properties (FMA)
FEMA — Annual competitive

BRIC — Building Resilient Infrastructure and Communities

Best fit for the CSO upgrade, culvert programme, and detention basin expansion. BRIC prioritises climate-adaptive infrastructure — combined sewer and drainage projects in communities with documented repetitive loss score highly.

Federal share: up to 75% of eligible project costs
Application: annual NOFO cycle — next window typically Sept–Nov
Your disaster declaration history increases scoring priority
Bundle culvert and detention projects to exceed $5M threshold for enhanced scoring
Full BRIC guide →
FEMA — NFIP-linked annual

FMA — Flood Mitigation Assistance

Direct fit for the repetitive loss acquisition and elevation programme. 4,200 identified RL and SRL properties represent a strong FMA application — SRL properties carry zero local match requirement.

SRL properties: 100% federal — no local match
RL properties: up to 90% federal cost share
Property owners must have active NFIP policy to qualify
Floodplain manager initiates as sub-applicant — begin outreach immediately
Full FMA guide →
HUD — Post-disaster

CDBG-DR — Community Development Block Grant Disaster Recovery

If your jurisdiction has had a recent presidential disaster declaration, CDBG-DR funds can cover the local match requirements for BRIC and FMA — effectively making federal mitigation grants available at near-zero local cost.

Can be used as local match for FEMA grant programs
LMI community benefit requirements — 70% threshold
Administered through state HUD grantee office
Application via state CDBG-DR program officer
Full CDBG-DR guide →
State — varies by state

State resilience and stormwater grants

Most states operate supplemental mitigation and stormwater programs that can fund projects below FEMA’s competitive threshold or cover the local match for federal applications. Check with your state hazard mitigation officer for current open windows.

Faster application cycle than FEMA competitive programs
Often no benefit-cost analysis required for smaller projects
State revolving funds (SRF) available for stormwater infrastructure
Contact your State Hazard Mitigation Officer for current availability
State programs guide →

Ready to take the next step?

Oiriunu connects your municipality with grant writers, floodplain management specialists, and vetted engineering partners who can move your priority projects from assessment to funded application.

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