How can you incorporate low impact development to your design?

December 18, 2014 by Amanda Saldivar

Low impact development (LID) is a site planning and engineering design approach to managing stormwater runoff.  Unlike traditional methods of storm water design, LID emphasizes conservation and use of on-site natural features to protect water quality.  This approach implements engineered small-scale hydrologic controls to replicate the pre-development hydrologic features of watersheds through infiltration, filtering, sorting, evaporation, and detaining.

Bio Swale
Bio Swale

Low impact development (LID) is a site planning and engineering design approach to managing stormwater runoff.  Unlike traditional methods of storm water design, LID emphasizes conservation and use of on-site natural features to protect water quality.  This approach implements engineered small-scale hydrologic controls to replicate the pre-development hydrologic features of watersheds through infiltration, filtering, sorting, evaporation, and detaining.

Traditional approaches of mitigating storm water includes conveying stormwater quickly from the site to a detention pond or managing peak flows from the development into a regional storm system. These large scale systems may require large land area or expensive construction costs. When implementing LID, the approach of managing storm water includes treating storm water on-site and using it as a resource upon being treated. Instead of focusing on diverting storm water quickly off of the site, LID increases the time storm water is able to remain on site thus promoting infiltration and reuse of water. This new approach reduces the level of pollutant loads to the local bodies of water and utilizes the storm water for irrigation or other onsite uses. In certain cases these options may even be more cost effective than traditional storm water measures.

Rain GardenRain Garden 

LID designs may take on many forms to minimize and help prevent concentrated flows of storm water leaving a site. They integrate green space, native landscaping, natural hydrologic functions and other various techniques to generate less runoff from developed land. This involves strategic placement of permanent controls that are customized to address specific pollutants and storm water timing, flow rate, and volume issues. LID development can also add value and flexibility to a site’s landscape areas and green space and often appears to be planting beds, usable grassy areas onsite, or trees used to soak up water.

The ten common practices of LID are below:

1. Permanent BMPs that promote infiltration:

    a. Bio-Retention
    b. Bio-Swales
    c. Permeable Pavement

2. Permanent BMPs that promote filtration

    a. Planter Boxes
    b. Green Roofs
    c. Sand Filter

3. BMPs for storage and reuse

    a. Stormwater Wetlands
    b. Rainwater Harvesting

4. BMPs that treat and convey stormwater

    a. Vegetated Swales
    b. Vegetated Filter Strips

Tree planter boxesTree planter boxes

Low Impact Development is still a new concept, one that has not been incorporated into the City of San Antonio’s drainage code and is therefore not mandatory. The San Antonio River Authority (SARA) has taken a strong position toward using these methods, going so far as to build a LID design handbook for San Antonio. When developing in and around the San Antonio River it is likely that SARA will request that LID methods be used by developers. SARA is pushing for this handbook to be adopted into the City of San Antonio Unified Development Code in 2015.

Although this option is new, it is likely that as our City continues to expand, LID will become a more common option for new development in urban and suburban sites. BIG RED DOG has significant experience in LID design and techniques and have designed permanent LID structures in various projects.

We’re happy to help you design and incorporate LID in your development design. You can contact us at (210) 860-9224 or email us at [email protected]

Written by Amanda Saldivar

Amanda Saldivar

Amanda Saldivar is an Assistant Project Manager in the San Antonio office. Amanda’s experience includes storm water management and conveyance design, storm water quality treatment methods and utility design. She is active in the American Society of Civil Engineers, Engineer’s Week and the Hispanic Chamber of Commerce. Her biggest projects include In-N-Out Burgers, CVS Pharmacy and Valero Corner stores.