The City of Austin Drainage Criteria Manual, known as the DCM, is the city’s binding engineering rulebook for how stormwater runoff must be managed on development projects inside the city limits and the surrounding extraterritorial jurisdiction. If your project adds impervious cover, disturbs significant soil, or changes how water flows across a site, you have to design to it. The current version is Supplement 19, published in April 2026.
Central Texas floods hard and fast, and the DCM exists to keep new construction from pushing more water, faster, onto someone else’s property or into an already strained creek. The sections below cover where the manual gets its legal force, which projects and locations fall under it, what it requires on the ground, and how the review and maintenance obligations work.
Where the Manual Gets Its Authority
The DCM is not a guidance document. It carries the force of the Austin Land Development Code. Title 25 of that code contains Austin’s development regulations and building technical codes, and Title 30 covers subdivision regulations that reach into the extraterritorial jurisdiction.1AustinTexas.gov. Codes, Resources, Tools Chapter 25-7 specifically addresses drainage and requires the director of the Planning and Development Review Department to approve plans and specifications for storm drains, bridges, and culverts before construction can begin.2Municode Library. Austin Land Development Code Chapter 25-7 – Drainage
The DCM translates those broad legal mandates into page-by-page engineering requirements. It sits alongside the Environmental Criteria Manual, which governs water quality protections, and the Standard Specifications manual, which covers construction materials and methods. Design professionals usually need to reference all three.
Austin’s stormwater program also answers to federal law. The Clean Water Act’s National Pollutant Discharge Elimination System requires municipal stormwater permits to effectively prohibit non-stormwater discharges and to reduce pollutants to the maximum extent practicable.3Office of the Law Revision Counsel. 33 USC 1342 – National Pollutant Discharge Elimination System The DCM is part of how the city meets that obligation locally.
Who Has to Comply
Any project that qualifies as “development” under the Land Development Code triggers mandatory compliance. That includes new construction, additions that increase impervious cover (rooftops, pavement, and other surfaces that shed rather than absorb rain), and significant land disturbance such as grading or clearing large soil areas. Even modest residential improvements can fall in scope if they change how water moves across the lot.
The geographic reach extends past the city limits. Subdivision projects in the extraterritorial jurisdiction also have to meet applicable drainage standards under Title 30.1AustinTexas.gov. Codes, Resources, Tools If your property sits anywhere near the metropolitan boundary, confirm whether it’s inside the city or the ETJ before spending money on design. Getting that question wrong early can mean expensive redesigns later.
What the Manual Requires on Your Site
The DCM’s technical requirements fall into three broad areas: calculating how much runoff a site produces, holding and releasing that runoff responsibly, and treating it for pollutants before it leaves.
Runoff Calculations
Before anything else, an engineer has to calculate how much water the site will generate in storms of various sizes, and the DCM dictates which methods are acceptable. For drainage areas of 100 acres or less with a time of concentration of two hours or less, the Rational Method applies. For drainage areas larger than 100 acres, engineers must use the Natural Resources Conservation Service Curve Number method, though that method can also be used on smaller sites.4Austin, TX. Drainage Criteria Manual – Section 2.1.0 General The Curve Number method accounts for soil type, land cover, and antecedent moisture, which makes it the better fit for larger, more complex watersheds.
Both methods need accurate rainfall data. The DCM uses precipitation frequency estimates from NOAA’s Atlas 14, delivered through the Precipitation Frequency Data Server.5National Oceanic and Atmospheric Administration. Precipitation Frequency Data Server Designs built on older or generic rainfall values will not pass review.
Engineers also have to analyze downstream effects. The project has to demonstrate that post-development runoff does not worsen flooding beyond the property boundary, which means modeling conditions well past the site itself. This is a frequent sticking point in review.
Detention Standards
Detention ponds temporarily hold runoff and release it slowly so downstream channels and storm sewers aren’t overwhelmed. The DCM requires detention facilities to reduce post-development peak discharge rates to pre-development levels for the 2-year, 10-year, 25-year, and 100-year storm events at each discharge point from the site.6Austin, TX. Drainage Criteria Manual – Section 8 Stormwater Management Matching all four return periods prevents the common failure where a pond sized only for the 100-year event actually makes smaller, more frequent floods worse.
Freeboard (the safety margin above the 100-year water surface) scales with drainage area, and ponds must drain completely within 24 hours of peak storage. That drawdown limit stops standing water from becoming a mosquito problem while still holding runoff long enough to shave the flood peak. Parking lot detention is allowed, but ponding depth during a 100-year storm is capped at an average of 8 inches with a 12-inch maximum.6Austin, TX. Drainage Criteria Manual – Section 8 Stormwater Management All detention facilities must be physically accessible for maintenance, and where off-site flows pass through a pond, the outlet has to safely convey 100-year fully developed flows from those off-site areas independently of the on-site detention function.
Water Quality Controls
Flood control isn’t the whole picture. The city also requires treatment of runoff to pull pollutants out before water reaches creeks and the Colorado River. The core strategy is capturing a minimum volume of the initial runoff, often called the first flush, which carries the heaviest pollutant load off parking lots, rooftops, and construction surfaces. The baseline capture starts at the first half-inch of runoff and scales up with impervious cover above 20 percent. Captured water has to be treated and released within 48 hours.
The Environmental Criteria Manual carries the detailed specifications for water quality best management practices, including bioretention filters, constructed wetlands, sand filters, and vegetated buffer strips. Water quality requirements can significantly affect site layout and grading, so the ECM should be on the desk alongside the DCM from the earliest design sketches.
The Drainage Report and the Review Process
Every project requiring drainage review submits a Drainage Report with the permit application. This is the single document reviewers use to decide whether the project meets DCM standards, and incomplete submittals are the most common cause of delay.
A complete report includes existing and proposed topographic maps, soil data and infiltration characteristics, the full hydrologic calculations with Atlas 14 rainfall data, delineation of all contributing drainage areas on-site and off-site, the downstream analysis, detention facility design with sizing calculations and freeboard verification, and drainage plan exhibits showing pipe sizes, flow directions, and outfall locations. The Watershed Protection Department publishes checklists that itemize every required data point, and the smart move is to use those checklists as the table of contents for the report rather than assembling it from memory. Completed reports become part of the public record and serve as the legal documentation that the project meets municipal drainage standards.
Submittals go through the Development Services Department, with technical review by Watershed Protection Department staff. Expect at least one round of review comments. Most projects go through two or three rounds before every issue is resolved, and ignoring or incompletely addressing a comment guarantees another round. Once Watershed Protection signs off, the drainage approval becomes a prerequisite for the building permit. No drainage approval, no building permit, regardless of how far along the rest of the project is. Timelines vary with complexity and current application volume, so treating the drainage submittal as a critical-path item from day one is the most reliable way to protect the schedule.
Maintenance Obligations After Approval
Approval and construction are only half the obligation. Ongoing maintenance of private stormwater infrastructure typically falls on the property owner. Detention ponds collect sediment, outlet structures clog, and vegetation can overtake engineered slopes. A pond that functioned perfectly on opening day can become a flooding liability within a few years without upkeep.
The city often requires a recorded maintenance agreement as a condition of approval. These agreements run with the property, meaning they bind future owners, and they spell out inspection schedules, maintenance tasks, and reporting requirements. Anyone buying a site with an existing detention facility should locate and read this agreement before assuming they know what they’ve inherited.
Practical maintenance means removing sediment and debris from inlet and outlet structures, inspecting embankment slopes for erosion or animal burrows, keeping emergency spillways clear, and confirming that any gates, valves, or trash racks still operate. Underground detention systems can require vacuum truck services and confined-space entry performed by trained professionals.
Neglect isn’t just a regulatory risk. A failed private detention facility that floods neighboring property can create significant legal liability for the owner. Regular maintenance costs a fraction of a structural failure or a flood damage claim, and it belongs in the operating budget for the life of the property.