Newly Updated: Floodplain (FEMA) Maps

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Homeowners, renters and business owners in Williamson County are encouraged to look over newly released preliminary flood maps in order to determine their flood risks and make informed decisions. 

County officials and the Federal Emergency Management Agency (FEMA) are presenting the preliminary maps to communities and unincorporated areas in Williamson County in order to help leaders and residents identify known flood risks and use that information to make decisions about buying flood insurance and any future development.

Interactive map with general overview of changes

Interactive map with detailed overview of changes

The Department of Homeland Security’s Federal Emergency Management Agency (FEMA) is in the process of releasing new floodplain maps for the portion of the City of Cedar Park that lies within Williamson County.  FEMA identifies floodplains in order to calculate flood risks for insurance purposes, particularly within Special Flood Hazard Areas (SFHA). SFHAs are defined as the area that will be inundated by the flood event having a one percent (1%) chance of being equaled or exceeded in any given year. The one percent (1%) annual chance flood is also referred to as the base flood or 100-year flood.

The new maps are a result of a multi-year study of the Upper Brushy Creek watershed prepared by the Texas Water Development Board (TWDB) and the Upper Brushy Creek Water Control and Improvement District (UBCWCID).  The City of Cedar Park was an active member of the Technical Advisory Committee for the UBCWCID watershed study.  The new floodplain maps are the result of new technology and data which yields a better assessment of where flooding is most likely to occur close to creeks and more accurately predict floodplain boundaries. In most cases, mapped drainage boundaries have not changed.


Floodplain Comparison Mapping Tool

Williamson County has prepared a simple mapping tool that compares the current effective floodplain limits to the proposed new floodplain limits. 

Mapping tool:

Simply click the blue “I want to…” button at the top left of the page to see a list of options.  Use the "Address Search" to enter an address and zoom the map into the appropriate area. 

The example below shows how the different colors indicate updated areas:

 No Change

 Areas to be removed from existing floodplain

 Areas to be added to existing floodplain

FEMA map

Alternatively, the links below are provided by FEMA to access the same information, however, the Williamson County webpage linked above is more user friendly.

On January 30, 2017, FEMA posted digital copies of preliminary Flood Insurance Rate Maps (FIRM), Flood Insurance Study (FIS) report materials, and supporting data on their Map Service Center website. Link:

The current effective data and preliminary flood hazard data can be compared though this interactive mapping tool. Link:

A “how-to” for this interactive map is also available. Link:


Frequently Asked Questions (FAQs)

Why are floodplain maps being updated?

The maps are being updated because the majority of the maps are based on analyses that were performed over 25 years ago. Watershed conditions such as topography have changed and there has been significant added development. Furthermore, analysis tools and historical data collection have improved over time and will increase map accuracy.

Flood hazard mapping is an important part of the National Flood Insurance Program (NFIP), as it is the basis of NFIP regulations and flood insurance requirements. The Federal Emergency Management Agency (FEMA) maintains and updates data through Flood Insurance Rate Maps (FIRMs) and risk assessments.


How often are these maps updated? 

There is no set timeline. Flood zone designations may be revised when new and more accurate information becomes available because of a FEMA-funded restudy or because the community makes the information available to FEMA. Several factors influence the frequency with which flood maps may be updated, such as the extent of new development and the completion of flood-control projects.

There are no comprehensive updates foreseen in next 10 years.


Who initiated the update?

FEMA initiated a partial update in 2010. In 2012, the Upper Brushy Creek Water Control and Improvement District (WCID) initiated a flood protection plan that included watershed modeling. Communities within the watershed desired to use the modeling as the basis for a comprehensive mapping update. The WCID then partnered with FEMA and the Texas Water Development Board to complete the process.


Where is this happening?

The updated maps encompass the Upper Brushy Creek WCID boundary, which includes much of southwest Williamson County.


What is the general impact of new floodplains? Are more properties going to be in the floodplain?

In general, updated flood levels will increase, i.e., more properties are likely to be in the updated floodplain. When new maps are issued, your risk may have changed along with your flood insurance requirements. Property owners are encouraged to review the updated maps and discuss implications with their insurance agent. If you've been mapped into a high-risk area, you will be required to purchase flood insurance if your mortgage is through a federally regulated or insured lender. It is possible to save money through a process known as grandfathering provided by the NFIP.

If your property is mapped out of a high-risk area, your flood insurance costs will likely decrease.

Who should I talk to if I have questions?

Property owners or other persons who wish to follow the progress of the PMR should consult their community's Floodplain Administrator. This is the local official who keeps all of the community's flood hazard maps and FIS report, and who corresponds with FEMA at various stages of the revision process.

For properties located in the City of Cedar Park, please contact the Engineering Department at

Or email:

The status of ongoing map revisions can also be checked on the FEMA website, or by calling the FEMA Map Information exchange toll free at 1-877-FEMA MAP (1-877-336-2627)


What is the plan for educating the public about this?

We will educate the public through our usual channels, including the City’s website, social media and working with the news media.


Why and how do I obtain Flood Insurance in Newly-Mapped Areas?

Mortgage companies usually require flood insurance for homes and businesses in the floodplain. There is a Newly Mapped Policy available for the first year when there are changes to floodplain maps. Download this FEMA document for more information:


Am I eligible for the NFIP Grandfather Rule?

The Grandfather rule may save money on flood insurance rates for qualifying property owners.  If a new flood map shows a high-risk property is at greater risk for flooding than shown on the previous map, the flood insurance rate will likely change.  The NFIP grandfather rule may save money by locking in the previous flood zone or the Base Flood Elevation (BFE) for insurance rating purposes after the new map becomes effective.  For more information, see the following link:


Additional information on floodplains provided by the City of Cedar Park and other related agencies:


Additional helpful links:

For floodplain related questions, please contact the City's floodplain personnel at:


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