Phoenix (Maricopa County), AZ Flood Zone & Drainage Map

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Overview

Where does rainwater drain in Maricopa County? This interactive map shows surface drainage patterns across Phoenix, Scottsdale, Mesa, and surrounding areas based on terrain shape - where gravity directs rainwater based on elevation and slope. For official flood risk information, see the FEMA flood zone layer on the Hazards tab.

Maricopa County's desert terrain creates extreme flash flood risk during monsoon season. Hard-packed caliche soil and sparse vegetation offer almost zero infiltration, converting intense rainfall directly into fast-moving sheet flow through dry washes. The Salt River, Indian Bend Wash, and Cave Creek are normally dry but can become raging torrents within minutes during summer thunderstorms. Choose a location to see surface drainage analysis and water flow direction based on terrain shape. The first three locations are free.

Interpretation

Select a location on the map or enter an address to see terrain analysis.

3D Terrain Visualization
Where does rainwater flow based on terrain shape? Blue areas show where water collects and drains downhill.
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Terrain drainage map of Maricopa County, AZ: modeled paths where rainwater runs and collects, from USGS 3DEP elevation data, with the county boundary Click any spot on the map to analyze it
4.0× Horizontal:Vertical
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Maricopa County flood history

FEMA records 2,633 flood insurance claims in Maricopa County since 1978, with about $26 million paid. 44% of the claims with a rated flood zone came from moderate- or low-risk zones (X, B or C), outside the high-risk areas on FEMA’s flood maps.

Among the 50 largest U.S. cities, Phoenix ranks #27 for FEMA flood insurance claims per home: 2.0 claims per 1,000 homes since 1978 (1,312 claims within city limits). See all 50 citiesA low rank doesn’t mean Phoenix is safe! Only insured buildings file claims, and local runoff can still flood a house here.

Bar chart of FEMA flood insurance claims per year in Maricopa County, AZ, 1978 to 2026, highest in 1978 with 317 claims.

Biggest flood years

  1. 1978 · 317 claims
  2. 1980 · 266 claims
  3. 2014 · 247 claims
  4. 1990 · 184 claims
  5. 1984 · 131 claims

ZIP codes with the most claims

ZIPClaimsShare
853532419.2%
850211515.7%
850181204.6%
852531064.0%
850131023.9%
852551023.9%
85014983.7%
85326983.7%

How to read this. These are National Flood Insurance Program claims, so they count only insured buildings and miss flooding where owners had no flood insurance. FEMA publishes them without names or addresses: they show which years and areas flooded, never whether a particular house did. ZIP codes are as reported on the claims, and a ZIP code can extend beyond the county. The “rated” flood zone is the one used to price the policy and may come from an older map. Data as of 2026-09-08, from FEMA OpenFEMA.

Sunlight and soil in Maricopa County

Sunlight. Ground here gets about 5.8 kWh of sunlight per square meter per day on average (5.5 to 6.0 across the map), above the middle of the lower 48 (4.5). South-facing slopes get more, north-facing ones less.

Soil. The ground is mostly loamy soil (Calcisols 23%, Cambisols 19%, Regosols 7%), with loamy soil over a clay-rich subsoil (Luvisols 21%). Rain soaks in at a moderate rate.

Sunlight: long-term average on flat ground from the National Solar Radiation Database (National Laboratory of the Rockies, formerly NREL). Soil: most likely soil types from ISRIC SoilGrids, a 250 m model, not a survey of any lot. Both cover the map area above.

Explore more flood and drainage maps

Browse all 64 flood and drainage maps · Flood insurance claims in the 50 largest cities · How Terreflow uses terrain and FEMA data