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Austin's drainage charge is assessed on utility bills and pays for solutions to flooding, erosion and water pollution.

Impervious Cover Update 2025

We are updating impervious cover data, which may result in some customers seeing changes to the drainage charge on their bill. For most accounts, the update will result in no change or a change of less than $1 per month. Accounts with the largest changes will receive additional notification via phone.

Drainage Charge Calculation

The drainage charge is calculated individually for each property, based on the amount and percent of impervious cover. Less impervious cover means a lower charge.

What is impervious cover? It includes:

  • Rooftops
  • Patios
  • Driveways, paved and unpaved
  • Parking lots, paved and unpaved
  • Other surfaces that do not absorb rainfall.

Impervious cover has a significant impact on stormwater. It increases the amount and speed of stormwater. It also increases the amount of pollutants in stormwater. To find out more about how impervious cover contributes to problems such as flooding, watch the Pervious v Impervious Cover YouTube video.

What is My Impervious Cover?

Use the Find My Drainage Charge tool to see the impervious cover on your property. The Find My Drainage Charge tool works best with Internet Explorer 9 or higher, Firefox, Google Chrome or Safari.

  • Go to Find My Drainage Charge tool
  • If your information is unavailable, it may be due to a confidentiality request by the account holder. For more information, visit the Austin Energy Confidentiality & Customer Rights page.
  • Impervious cover may not be shown if the property was recently developed after the latest aerial photography was taken.

Stormwater Management Discount

If you collect rain water on your property, you may be eligible for a discount on your drainage charge. The discount is available to both residential and commercial properties. However, you must exceed development requirements to be eligible. Find out more about the Stormwater Management Discount.

Estimate Your Drainage Charge

If you are planning changes to the impervious cover at your property, you can use this calculator to estimate your drainage charge.

Learn More

What is impervious cover?

The following information pertains specifically to the calculation and application of impervious cover for determining the drainage charge imposed by the City of Austin's Watershed Protection Department. 

Impervious cover is any type of human-made surface that doesn’t absorb rainfall, including: 

  • Rooftops
  • Patios
  • Driveways, paved and unpaved
  • Sidewalks
  • Roadways
  • Parking lots, paved and unpaved
  • Some decks 

Uncovered wooden decks and unpaved portions of driveways count as 50% impervious cover. If you have these features, we may be able to lower the impervious cover on your account, which will in turn lower your bill. Please call 512-494-9400 and ask about an administrative review of your drainage charge. 

A more complete definition of impervious cover is found in Section 25-8-63 of the Austin City Code. While impervious cover has broader implications in terms of urban planning and land development regulations, this information focuses on its connection to the drainage charge. For more comprehensive information about impervious cover regulations beyond the drainage charge, please refer to the appropriate resources and guidelines provided by the City's Development Services Department.

What is the drainage charge and why is it important?

The stormwater drainage charge is shown on your monthly utility bill in the Drainage Service section. It funds the City of Austin's drainage utility mission and is authorized by the Texas Local Government Code. 

The drainage charge was first adopted in 1982, the year after the 1981 Memorial Day Flood, which killed 13 people and caused $35.5 million in damage. 

The drainage charge pays for a wide variety of programs to help with flooding, erosion and water pollution across Austin. Many projects and programs are working quietly behind the scenes to protect lives, property and the environment. Crews clean trash and debris from Lady Bird Lake, maintain our drainage infrastructure, and respond to more than 3,000 service requests annually. Staff respond to reports of environmental spills and emergencies 24-hours a day. They coordinate numerous projects to help reduce the risk of flooding and erosion.

How does the City know how much impervious cover is on each property?

The impervious cover data is generated using aerial photography collected every two years. Each pixel on the aerial photography represents 6 inches on the ground. The accuracy is suitable for defining the edges of buildings, patios, driveways, and other types of impervious cover. This data was used to create impervious cover maps seen on the Find My Drainage Charge Map Tool. (For best results, use Internet Explorer 9 or higher, Firefox, Google Chrome or Safari.) 

For properties developed or modified after the latest aerial photography, we use building permit data. Bills are typically adjusted based on the latest aerial photography in February during odd-numbered years. 

Drainage Charge for Commercial and Multi-Family Properties

The drainage charge is calculated the same way for everyone based on the amount and percent of impervious cover such as driveways, rooftops, parking lots, patios and walkways. 

Property Owners or Representatives 

For multi-family properties with five or more units and for properties with multiple businesses located on them, the City will bill the property owner or their representative for the drainage charge, whenever possible. Prior to November 2015, the City billed individual vacant or occupied units. The City bills individual residents for duplexes, triplexes and fourplexes, dividing the charge evenly among the units. 

Allocating the Charge 

Property owners may pass the drainage charge on to their residents or tenants. Whether and how they choose to allocate the charge to each unit is up to them as the bill payer for the property, keeping in mind any applicable provisions in their lease agreements as well as the requirements in City Code Chapter 15-9 (Utility Service Regulations). Property owners may download the Notice to Apartment Residents (pdf) and/or the Notice to Businesses (pdf) and provide a copy to their residents. 

Billing Concerns

Your drainage charge is based upon the amount and percent of impervious cover at your address. The impervious cover data was collected through aerial photography, LIDAR data and development records. We review and update our data on an ongoing basis as more information becomes available.

If, for any reason, you think there’s an error in your drainage charge, please fill out the Drainage Charge Inquiry and Support form or call our Customer Care Center at Austin Energy at 512-494-9400 to let us know. This is the first step to initiate a review of your account. Here are some things you may want to be aware of before you call: 

  • You can check the impervious cover at your property using the "Find My Drainage Charge" tool.
  • The City’s data on your impervious cover may not be the same as the appraisal district’s improvement values on your tax assessment. That is because the City includes driveways, walkways and other impervious areas not reported in the appraisal district data.
  • In some cases, the shaded impervious cover shown on the map does not line up with the photograph beneath it. This is due to the aerial photography being taken at an angle, but it does not affect the amount of impervious cover. This is particularly likely to occur with tall buildings.
  • The monthly charge per square foot of impervious cover is less than a penny, so small discrepancies in the amount of impervious cover may have little impact on your bill.
  • We may be able to lower your bill if you have an uncovered wood deck or an unpaved section on your driveway.
  • Frequently, there is no change to the drainage charge after a review.
  • Occasionally, the drainage charge increases after a review. This typically happens when we are reviewing impervious cover in one area of the property, but discover impervious cover in another area, sometimes covered by trees or newly built.
  • You may be asked to provide supporting documents, but often we can resolve your request through a phone call.
  • You may be asked to provide City staff access to your property to verify your information. 

Administrative Review and Hearing 

City Code section 15-2-12 and City Code Chapter 15-9 Article 12 are the relevant sections of the City Code for disputing your drainage charge. An administrative review by the Watershed Protection Department comes first. During this process, which is initiated by a customer call, City staff will review your records to verify the information that you provide. If you are not satisfied at the conclusion of this review, you may request an administrative hearing by an independent hearings officer. 

Paying Your Bill 

While your account is being reviewed, you remain responsible for paying the bills you have received. We will issue you a credit (or extra charge), if it turns out there has been an error. 

Assistance Paying Your Charge 

Residential customers may request a reduced drainage charge based on financial need through the Customer Assistance Program. This discount on the drainage charge is only available to those being billed directly by the City for drainage. It is not available to residents of multifamily dwellings for which the property owner or owner’s agent pays the drainage charge. 

Documents and Resources