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There are more than 9,000 buildings in the 100-year floodplain in Austin. In addition, more than 300 bridges are subject to flooding. We plan, design and construct projects to help reduce flood risk  and protect the public from the devastating impacts of flooding. 

Projects are prioritized to help the most homes with the most severe flood risk . We also modernize and upgrade existing detention ponds, dams and low water crossings. 

This page summarizes the process of our work and highlights several projects. 

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Solutions for Creek Flooding

It can be challenging to reduce flood risks along our creeks. It means finding a safe way to manage an incredible amount of fast-moving water that must go somewhere without negatively impacting other property owners. In some cases, we cannot find a workable solution. Some options that may be effective are:

  • Buyouts to convert floodplains back to open space and help families find safe housing away from flood prone areas
  • Bypass tunnels to divert stormwater away from a flood-prone part of the creek
  • Channel modifications to provide more capacity in the creek
  • Detention ponds to hold some stormwater back and release it in a controlled manner. Despite their names, detention ponds are usually dry and are required to drain within 24 hours after a storm.
  • Flood walls to provide more capacity in the creek

Each of these potential solutions has benefits and drawbacks. They are not always suitable for a particular situation. 

Dam Modernizations

Some detention ponds are classified as dams depending on the height of their embankments and how much water they hold. We sometimes need to repair or modernize these dams in Austin. Priority is given to “high hazard dams.” This is a classification by the Texas Commission on Environmental Quality and refers to dams that might cause loss of life or significant economic damage if they fail.  

Low Water Crossing Improvements

Low water crossings are dangerous during floods, and people continue to drive through flooded roadways for a variety of reasons. We are sometimes able to make improvements to a low water crossing or bridge to make it safer during a flood. We prioritize ones that provide the only access into and out of an area. We also take into account how often a road floods.

No Adverse Impact

When looking at ways to reduce flood risk, it’s important that we don’t simply shift the problem to someone else. We must evaluate the potential impact of our projects and take steps to prevent worsening of the floodplain downstream of the project. This may take the form of a detention pond, widening of the channel, or additional drainage easements to give the water more space. It can be the most challenging part of a project. 

Easements

We sometimes need to purchase easements to complete our projects. An easement can be  temporary, needed during construction, or permanent. There are many different types of easements, but they all give the City limited rights of access or use. 

Drainage easements are particularly common for our projects. They are generally needed either to access and maintain infrastructure or to provide a place for water to flow. Residents should not build fences, walls, sheds or buildings within a drainage easement. They should be used for grass or flowers.

Process

Our capital improvement projects take many years from start to finish. The process typically includes the following phases:

  • Feasibility Study – when information is collected to identify potential solutions.
  • Preliminary Engineering – when a solution is identified and costs are estimated.
  • Design and Permitting – when the details are worked out, construction plans drawn up and permits are acquired. Easements, if needed, are usually acquired during this phase as well.
  • Bidding – when a contractor is hired.
  • Construction – when the project is built.

Construction is dependent upon the availability of funding. In some cases, we are not able to identify a feasible or cost-effective solution during the first two phases.

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Resources

Project Summaries

McNeil Drive Low Water Crossing Improvements

This project will replace the low water crossing on McNeil Drive with a bridge. Currently there are two 36-inch culverts at the low water crossing. We will replace them with three 10-foot by 6-foot box culverts. The new bridge will reduce the frequency of road closures due to flooding and improve neighborhood access during storms. . There will be no changes to the traffic lanes.

The current low water crossing was closed 22 times between 2014 and 2018. Computer models show three feet of water over the road in a relatively small storm, known as a 2-year storm. This type of storm has a 50% chance of occurring in any given year. In a 100-year storm, or one that has a one percent change of occurring in any given year, the road will be overtopped by more than four and half feet of water.

Watershed

Tributary 9 of Walnut Creek

Location

The low water crossing is on McNeil Drive, just west of MoPac. View map of project location.

Opinion of Probable Construction Cost

$1.4 million

Status

We completed the preliminary engineering phase in the spring of 2019 and are currently acquiring permits. Construction is anticipated to begin in 2026.

Documents

Questions

Please reach out to one of the following people:

Middle Williamson Creek Flood Risk Reduction

We are evaluating ways to reduce the risk of flooding for buildings in the floodplain along the middle section of Williamson Creek. Three alternatives stand out as having the most potential:

  • Optional buyouts
  • Creek modifications
  • Bypass tunnel

We are taking into account the effectiveness, costs, challenges associated with implementing the project, and public input for each alternative.

Background

This area experienced serious flooding in 1998, 2001 and 2013. After the floods in 1998 and 2001, we partnered with the U.S. Army Corps of Engineers and evaluated widening the creek, raising bridges, detention ponds and buyouts. Public meetings and surveys were conducted between 2002 and 2006. Ultimately, the U.S. Army Corps of Engineers found that only buyouts in some areas met their funding criteria and provided full flood protection. The City of Austin bought houses in the Bayton Loop area near West Gate as a result.

In 2015, as Phase 1 of this project, we offered buyouts in four more areas between Menchaca and South Congress. 53 households chose to sell their homes and move. About 400 buildings remain in the floodplain in this area.

Watershed

Williamson Creek

Location

This project includes the middle portion of Williamson Creek from West Gate to South Congress Ave.

Phasing

This project has two phases. Phase 1 has been completed.

Easements

Some alternatives will require the purchase of easements.

Status

We are currently in Preliminary Engineering for Phase 2.

Opinion of Probable Construction Cost

All three alternatives are costly, ranging between $20 million to more than $600 million.  We would need to secure funding before implementing any of these projects. In the past, similar projects have been funded through a combination of federal grants, drainage utility funds and different types of bonds. 

Documents

Questions

Please email MiddleWilliamsonProject@austintexas.gov or call 512-974-1347.

Northwest Park Dam Maintenance and Modernization Project

This project will improve the function of the dam and detention pond within Beverly Sheffield Northwest District Park. Please note that the detention pond is usually dry. The duck pond is not part of the stormwater facility.

The dam and detention pond were constructed in 1986. They are in need of heavy maintenance. They also need to be modernized to meet safety standards and protect the dam’s structural stability. This project includes:

  • Adding overtopping protection to the top of the embankment
  • Repairing erosion that has occurred on the creek side of the embankment
  • Removal of woody vegetation on the embankment
  • Protecting the embankment from erosive foot traffic within the park
  • Reinstalling drainage behind the retaining walls
  • Sealing cracks and joints within all retaining walls
  • Reestablishing positive drainage near the tennis courts
  • Reestablishing positive drainage near the duck pond

We are also evaluating several ways to improve water quality in this part of Shoal Creek with this project.

About the Dam and Detention Pond

Beverly Sheffield Northwest District Park has a dual purpose. During dry weather, the area is a district park. During wet weather the area holds stormwater to reduce flood risk to properties along Shoal Creek. During storms, Shoal Creek rises and water enters the park near the tennis courts.  As the creek rises, so does the water level in the park. As the amount of water in the creek decreases, the water in the park will start to drain through two outflow pipes. One of these pipes is near the duck pond and the other pipe is near the south parking lot by the baseball field. There is also an auxiliary spillway near the baseball fields. In extremely large storms, this is where water reenters the creek once the stormwater pond is full.

See a graphic of the dam.

Watershed

Shoal Creek

Location

This project is located within Beverly Sheffield Northwest District Park, 7000 Ardath Street.

Status

The project is currently in design.

Documents and Links

Questions

Oak Acres Flood Risk Reduction

This project will upgrade the low water crossing on Oak Blvd. and improve the roadside ditches and culverts.

View map of proposed improvements.

Bridge Upgrade

During heavy rainfall, the low water crossing can become flooded, cutting off all access to the neighborhood. We are proposing to replace the low water crossing with a bridge that will significantly improve access during storms.

The bridge would consist of two travel lanes, 10 feet in width, the same as the existing travel lanes. For pedestrian and driver safety, we would also add a curb and sidewalk on each side of the bridge, creating a seven-foot buffer from cars on either side. There will be a railing on the outside of the bridge. There will be ramps connecting the sidewalks on the bridge to the street near each of the four corners of the bridge. There are no current plans to add sidewalks in other parts of the neighborhood. View graphic of bridge

Roadside Ditches

We are proposing to upgrade the culverts and ditches on Oak Blvd. The size of the improved ditches varies from approximately two to three feet deep. At the top, most of ditches would be about 15 feet wide. We have adjusted the original plans to allow for more parking on Oak Blvd. North.

Residents are responsible for mowing and routine landscape-type maintenance.

Gaines Tributary Downstream of Oak Blvd.

The Gaines Tributary starts just upstream of the neighborhood, flows towards Southwest Parkway, passes Mopac and then flows into Barton Creek. The tributary slows down and spreads out after passing Oak Blvd. as the land becomes flatter with less of a slope. We have heard concerns that water is backing up downstream of Oak Blvd. The change in slope is the primary cause of this flow pattern. However, giant cane and bamboo have become established in the creek and could also be slowing down the water. We plan to remove these invasive plants within the drainage easement when we install the bridge.

Trees

Trees are important to us, and we try to affect as few as possible. However, we will need to remove  trees for this project. View these sheets from the plans for more information on trees.

Oak Hill Parkway

We have worked closely with TxDOT and reviewed the Oak Hill Parkway design. We do not believe it will impact drainage in the Oak Acres neighborhood.

Watershed

Gaines Tributary of Barton Creek. The area sometimes also receives flow from Williamson Creek.

Location

This project is on Oak Blvd. in the Oak Hill area.

Easements

This project includes both temporary easements for construction and permanent drainage easements.

Status

The Oak Acres project is currently in the permitting and bidding phase. Construction is anticipated to begin in late 2025.

To receive email updates, please send an email to Stephanie Lott

Opinion of Probable Construction Cost

$5.6 million

Documents

Questions

Please reach out to one of the following people:

Paces Mill Flood Risk Reduction

This project aims to reduce the frequency and depth of flooding from the Paces Mill drainage channel. Currently, there are 15 homes which are expected to flood in a 100-year flood. This is about 12 inches of rain in 24 hours and has a one percent chance of happening in any given year.

The project consists of channel improvements.

Watershed

Onion Creek

Location

The project is in the Yarrabee Bend South subdivision, northwest of the intersection of Thaxton Road and Salt Springs Drive. The project will focus on the drainage channel behind homes on Paces Mill Lane. View a map of the project.area.

Status

We are in the design phase.

To sign up for email updates for this project please visit www.publicinput.com/pacesmill 

Opinion of Probable Construction Cost

$8.3 million

Documents

Questions

Please contact one of the following people:

 

Don’t see your project? It may be considered a local flood, erosion or water quality-related project. A complete list of Capital Improvement Program projects is available on Capital Project Explorer.