Conservation landscaping stormwater credits

​Engineer Resources
Download Excel worksheet to calculate water quality volume and the size of permanent water quality management features under the Highland Lakes Watershed Ordinance.

 

conservation_landscaping2_1.jpgNew residential and commercial development projects located near the Highland Lakes can avoid the construction and maintenance of costly water-quality basins by limiting impervious cover to 15 percent or less of the development.  (See the Highland Lakes Watershed Ordinance for specifics.)

Developers can achieve this 15 percent target, and help maintain the region's water quality, through the use of this stormwater credit program — the only one of its kind in Texas.

Here's how it works:

Developers and builders use native landscaping, improved soils and other innovative techniques to limit stormwater runoff.
They then earn stormwater credits that can help gain compliance with the alternative standards in the Highland Lakes Watershed Ordinance. These alternative standards allow them to avoid constructing expensive water-quality basins to capture runoff.

An example of a 100-acre development
For the purposes of calculating a stormwater credit, conservation landscaping is applied to all lots within a development. For example, consider a 100-acre planned development that has 20 percent impervious cover. Here are the steps to obtain the credit:

  1. By planting native vegetation throughout the project area and following the guidance in the technical manual the project's impervious cover is reduced 5 percent — to a total of 15 percent.
  2. Next, the designers plan the development with flow paths and open-section roadways that mimic natural drainage patterns to satisfy the alternative standards design requirements.

​Q&A
​What is impervious cover?
It is impermeable surfaces, such as pavement, sidewalks and rooftops that prevent the infiltration of water into the soil.

Why limit impervious cover?
By limiting impervious cover, water runoff is reduced because more water is absorbed into the ground. Water runoff is the single largest source of pollution in the Highland Lakes. So, by limiting impervious cover we are working together to maintain water quality.

What is conservation landscaping?
Conservation landscaping is one of the chief ways to earn stormwater credits. It involves using limited turf area, preserving natural vegetation, and planting native trees, shrubs, and perennials to filter stormwater runoff and minimize the use of chemicals. These practices are well-known ways to reduce stormwater runoff and to improve the quality of the water running off a development.

There are four major components that increase landscape sustainability:

  • Adequate quantity of high quality soil
  • Implementation of efficient irrigation
  • Appropriate turf and plant choice
  • Proper installation

Are there other ways of obtaining stormwater credits to help gain compliance with the LCRA Watershed Ordinance?
Yes. Other methods to obtain stormwater credits include using porous pavement, preservation of natural areas, rainwater harvesting and other techniques. For more information on these and other stormwater credits see section four of the LCRA technical manual.

waterqualitybasinspring2010_t.jpg The bottom line: By using such techniques, costly and maintenance intensive water-quality basins are not required to gain compliance with the Highland Lakes Watershed Ordinance.

Vegetation best suited to local climate, soils
Conservation landscaping relies on native vegetation that is best suited to local climate and soils. Native vegetation requires less water and is more adaptive to semi-arid Central Texas and the Texas Hill Country. Using native plants will increase plant survival and decrease the cost of subsequent plant replacement.

Saving time and money
Homeowners save time and money. The initial costs of native plants, trees, shrubs, and soil amendments are recouped through significant reductions in water, fertilizer and pesticide use, as well as increased plant survival within the first few years after planting. Moreover, conservation landscapes require less time to maintain a high-quality lawn when compared with more typical landscapes. Learn more about Hill Country landscapes.

​Drawings
​Click on thumbnails to see larger views of drawings.
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Example showing one-half acre lot.

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Example showing one-fifth-acre lot.

The drawings (in box to right) provide color schematics with examples of how conservation landscaping can be applied to lots of one-fifth and one-half acres. By using good land practices, following natural drainage paths and limiting impervious cover to 15 percent or less, a residential development is not required to construct water-quality basins.

Conservation and native landscaping is not only useful in residential landscapes, it is appropriate in other landscapes, such as parks, schools, commercial sites, parking lots and apartment complexes.

More examples of conservation landscaping
Click on these images for larger views:

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For more information on stormwater credits contact us through Ask LCRA or call (512) 473-3200 Ext. 2091.