Blog · October 14, 2026 · California
Antioch Flood Zone Map: checking a property's flood zone
Flood zones are set by FEMA, and checking one near Oakley takes a few minutes.
Main page: Contra Costa County, CA GIS & Parcel Viewer (official map link, county facts and neighboring maps).
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Weighing a property around Pittsburg? Checking the Antioch flood zone map reveals whether the lot falls inside a mapped floodplain, and no account is needed. In this Antioch guide: finding the address on FEMA's map, reading the zone codes, and matching it with the county parcel viewer.
Getting started with the Antioch flood zone map
Flood zones come from FEMA's Flood Map Service Center: search an address around Oakley, and pick the FIRMette or map view. A tract near Walnut Creek without an address can still be found: search the nearest road and click the spot.
Getting to the right map
Parcels around Concord can be looked up on the Contra Costa County parcel viewer, which opens without registering. If you only know roughly where the land is, zoom in from Brentwood and select the outline. On ground around Clayton, the parcel card usually lists the owner of record, acreage on the tax roll, a parcel ID and in many cases the last transfer.
A quick look at the area
Martinez holds the county offices, which is where the courthouse records live. Other places on the map include Brentwood, Oakley, Pittsburg, and Clayton, where town lots give way to larger tracts. Roughly 1,155,025 people live in Contra Costa County (Census Bureau estimate, 2023) on roughly 717 square miles. Features like Clayton-Marsh Creek-Greenville Fault, San Pablo Dam Reservoir, and Mount Diablo State Park help you orient on the aerial around Pittsburg.
Where Antioch fits in
Antioch is part of Contra Costa County, California, and the county assessor maps its lots. For a home near Brentwood, city or town hall handles matters such as zoning, permits and utilities inside its limits, and the county still keeps the parcel and deed records. Lots just outside the town limits near Clayton usually falls under county rules instead.
On site with the map
The parcel map usually runs in a mobile browser, handy when you're parked on a road near Walnut Creek, but coverage can be spotty out of town. A screenshot of the parcel near Brentwood with its ID is a good backup.
Land on the county line
Contra Costa County touches Alameda County, Marin County, Sacramento County, San Francisco County, and San Joaquin County, all with their own assessor records. A tract near the line by Oakley may be split across two assessors' files, so open the neighboring map as well. With a lot near Oakley, our state page lists each neighboring county map for California.
What the zone letters mean
Zone AE comes with a base flood elevation, and an unnumbered A zone has none; surveyors near Clayton use that number. For acreage around Oakley, shaded Zone X marks moderate flood hazard, between the 1% and 0.2% annual chance floods; unshaded X is minimal risk.
Legal descriptions in California
California uses the Public Land Survey System, so rural legal descriptions near Walnut Creek cite section, township and range. Each section is nominally a mile square, about 640 acres, and a township holds 36 of them, though real sections near Clayton vary in size. Copy the legal description from the record for the parcel near Concord when you talk to a surveyor.
Lining it up with the parcel map
Where a floodplain cuts across acreage near Brentwood, the structure's footprint is the key question.
Low spots and local drainage
Low-lying fields near Clayton aren't always studied in detail, so look for water marks and debris lines. Marshy spots near Clayton can limit building too; check the National Wetlands Inventory mapper for a first look.
Questions to ask before you buy
Ask the listing agent about past flood claims for the house near Clayton; an insurance quote early keeps the budget honest.
Insurance, lenders and building
Out toward Clayton, get the Elevation Certificate if one exists: it can change the insurance price a lot. New construction in a floodplain near Walnut Creek often needs a floodplain permit; check with the county or town building office before you plan.
Getting answers from the right desk
Anything recorded against property around Brentwood sit in the index kept by the County Recorder, often with an online index. Zoning, permits and septic questions near Walnut Creek are for the local planning and health departments, town or county, depending on location.
Deeds, plats and who keeps them
The map is an index, not the title: deeds, subdivision plats and easements for land near Oakley are filed with the County Recorder. If the land is near Walnut Creek, use the book and page from the tax record so staff can find the deed fast.
Antioch: common questions
What is a LOMA near Clayton?
In most cases, FEMA's LOMA process is the usual route when a building near Walnut Creek sits above the base flood elevation, and lenders accept the result.
What is a base flood elevation in Antioch?
In most cases, the base flood elevation is the water level expected in the 1% annual chance flood; surveyors near Brentwood use it often.
Do I need to worry about flooding in Zone X around Concord?
Usually, X zones around Concord are lower risk, not no risk; FEMA notes that a large share of claims come from these areas.
Is AE a high-risk flood zone around Pittsburg?
Usually, AE is a Special Flood Hazard Area with a published base flood elevation, which shapes building rules near Oakley.
Why don't the lines match my fence near Walnut Creek?
The map near Oakley is approximate; a survey sets the real corners
Open the official Contra Costa County, CA parcel map See it in the Platbookmapper directory
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey, especially for fences, setbacks, or boundary disputes.