Discover How Impervious Cover Works from a Commercial Real Estate Broker in San Antonio

  • February 27, 2023
Impervious Cover Image

Did you know that there are over 50 major trailheads in San Antonio? Greenways, which are outdoor spaces that connect people and places, are an important part of the city. They are considered pervious cover. Pervious cover is the areas of land that are occupied by trees, lawns, mulch, and other natural materials. They permit rainwater to permeate them, keeping from a build-up of stagnant water puddles and reducing the need for drain systems. Now, let’s dig into the opposite material type—impervious cover.

What is impervious cover?

Impervious cover is the total area of any human-made surface that prevents the infiltration of water into the ground, meaning it does not absorb rainfall. Examples include patios, driveways, rooftops, sidewalks, parking lots, and roadways. Even buildings or structures that are raised above the ground, such as pier and beam foundations, are considered impervious cover. A commercial real estate broker in San Antonio can help you determine what is considered impervious cover on your property.

Impervious cover allows stormwater to pick up more silt and pollutants (including fertilizers, gasoline, and oil). The velocity and force of stormwater are increased, as well. This results in greater storm damage, bank erosion, and flash flooding.

How is impervious cover data generated?

To generate impervious cover data, aerial photography is collected every two years. In these photographs, which can originate from satellite images or air photos, each pixel is representative of six inches of land. It is suitable for defining the edges of various types of impervious cover. Any properties that are modified or developed after the most recent aerial photography work with building permit data to determine impervious cover.

Thematic maps are also used for municipal governance applications and land management. These are single-top maps focusing on specific themes. In the case in point, these maps are land cover maps. Several types of classification systems are used to categorize land cover, and the complexity of the map is dependent on the anticipated use of the data. But a typical land cover map includes buildings, roads and railroads, and other impervious surfaces.

Why are there impervious cover limitations?

When a property is subdivided, impervious cover limitations may be established. These limitations are adopted to minimize negative flooding effects that come from stormwater runoff. They also control water pollution that results from runoff, whether it be rainwater or other sources. When submitting an application for a commercial development project, you need to demonstrate that your property will not exceed maximum impervious cover limitations.

Impervious cover limitations are crucial for a number of reasons. For San Antonio properties, these limitations specifically protect the Edwards Aquifer from chemicals. This is a unique groundwater system that is one of the most prolific artesian aquifers in the world. Note that appropriate impervious cover limitations may differ in other parts of the city, outside of the aquifer recharge zone. Make sure to talk to a commercial real estate broker in San Antonio if you have any questions about your subdivision.

How is impervious cover calculated?

For mixed-use projects, impervious cover is calculated with the following simple formula:

Total Impervious Cover = A*60% + B*80%

A = % of multifamily residential ground floor

B = % of commercial ground floor use

60% = multifamily residential impervious cover allowance

80% = commercial impervious cover allowance


In impervious cover calculations, the following are excluded (but not limited to):

  • Multi-use trails that are open to the public
  • Drainage swales and conveyances
  • Sidewalks in a public right-of-way
  • Solar screen tents
  • Uncovered horse corrals
  • Detention basins (does not include subsurface detention basins)
  • Water quality controls (does not include subsurface water quality controls)
  • Weed screens
  • Areas with gravel over pervious surfaces
  • The water surface area of ground-level pools, ponds, and foundations

What are transferable development rights?

Transferable development rights are programs that are designed by local governments to allow for the free market transfer of development or subdivision rights. This transfer moves from rural zones to a jurisdiction’s designated development zone. A land developer purchases rights at market value from a landowner. Common attributes of successful programs include working in conjunction with other preservation programs, inter-jurisdictional cooperation, and embracing a healthy level of development activity.

Essentially, with transferable development rights, the land is permanently protected with conservation value. It is a flexible tool that can fit many different types of land and growth management scenarios. Commercial real estate brokers in San Antonio understand that transferable development rights programs are only effective when designed around real estate market forces.

Are there other site development standards?

There are site-specific challenges anywhere you go. On top of a site’s geographic location, development plans can be complicated by local zoning and land-use requirements. With that in mind, it is critical that you understand the circumstances surrounding your unique San Antonio site so that you can create a comprehensive strategy to overcome any challenges. It is a good idea to utilize the expertise of real estate professionals. Here are three things that every commercial real estate broker in San Antonio will consider.

Traffic Impact

Local leaders and residents alike have concerns regarding traffic. Many development projects impact roadways, resulting in increased traffic and ultimately more frustrated drivers. You must plan for this by conducting a traffic implant analysis. A traffic impact analysis is an engineering study that evaluates if nearby transportation infrastructure is able to accommodate the proposed development. Either the applicant or their consultant must identify their jurisdiction and consider project location, phases of construction, land use, density, and access points. Because each jurisdiction has its own guidelines, applicants are expected to receive approval for their scope of work prior to completing their traffic impact analysis.

Environmental Regulations

You likely already understand that development impacts the environment. However, if this is your first time executing a land development project, you must take the time to familiarize yourself with local ecosystems. Are there any open-space requirements, for instance? A large portion of San Antonio sits on top of the Edwards Aquifer, so a geological assessment might be necessary, as well. Because Edwards Aquifer is a vital drinking water supply aquifer, you must be considerate of the Texas Commission on Environmental Quality. This is responsible for approving water-quality protection plans. Environmental setbacks and development requirements, including impervious cover, vary based on local watersheds.

Utility Entitlements

Essential concerns around water continue with water and wastewater capacity. In the majority of cases, this is provided by the San Antonio Water System. Created in 1992, this is a public utility owned by the city of San Antonio. The mission of the San Antonio Water System is to provide sustainable, affordable water services. Going into a development project, you must determine whether your property’s needs are met by the water systems. If your existing infrastructure cannot meet those needs, a commercial real estate broker in San Antonio will tell you that budgeting for utility upgrades is a must.


Commercial Industrial Properties has been serving Texas since 1975. We have longtime brokers who are highly experienced in recommending and implementing strategies for businesses. With our expertise, you are sure to get the best deal possible with your real estate investment, whether it’s retail, office, land, or industrial. Get in touch with our team of commercial real estate brokers today to start diversifying your portfolio.


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