What is a Rain Garden?

January 5, 2016 by Chance Terrian

(Answer specific to the City of Austin)

Simply put, a Rain Garden is a shallow depressed landscape feature designed to capture and hold storm water runoff with the end goal of providing both filtration of pollutants and decreased runoff.

Rain gardens work by using the natural filtration properties of native plants and biofiltration media to remove pollutants. Microbial action is provided by bacteria and microorganisms in specially selected soil media.

Figure 1.6.7.H-3 from City of Austin Environmental Criteria Manual detailing a Full Infiltration Rain Garden
Figure 1.6.7.H-3 from City of Austin Environmental Criteria Manual detailing a Full Infiltration Rain Garden

Uptake, absorption, and transpiration are provided by native plants. Soil particles and roots systems inhibit the movement of pollutants, keeping them from reaching our creeks and rivers. And since storm water does not immediately enter a conventional hard-piped storm system, sudden surges of runoff are limited which is associated with flooding and erosion. Generally, the combined efforts of plants and media in providing water quality measures is referred to as Bioretention.

rain garden 1
Rain Garden near Cell Phone Lot at Austin Bergstrom International Airport

 

The City of Austin uses three different types of Rain Gardens. Design and construction requirements can be found in the City of Austin Environmental Criteria Manual, Section 1.6.7.H.

  •   full infiltration (no underdrain);
  •   partial infiltration (filtration system with raised outlet or partial underdrain); and
  •   filtration system with no infiltration.

Detailed sizing and calculation requirements can be found in appendix R-11, of the City of Austin Environmental Criteria Manual.

Rain Garden under construction at Multnomah Village. Portland Oregon.
Rain Garden under construction at Multnomah Village. Portland Oregon.

When designed properly, rain gardens serve as both infrastructure and amenity. BIG RED DOG can design a rain garden on your next project like we did for many of these clients. We look forward to hearing from you.

Written by Chance Terrian

Chance Terrian

Chance Terrian takes pride in being one of the top CAD designers working in Texas. He has over 16 years of professional experience in civil engineering design, permitting and construction administration. That experience includes roadway design, water & sewer design, grading, drainage, pond design, cut & fill analysis, exhibits, details, sections, and everything else required for completing retail, multi-family, single family, and commercial projects in both public and private sectors. He’s also known around town for his unwavering attention to detail, natural talent for problem solving, and superior designs. In addition to his accomplishments in fully designed and breathtaking construction plans, he is also responsible for BIG RED DOG’s CAD standards, CAD training and implementation programs. With the help of our other Principal CAD experts, he has created the template that makes all of BIG RED DOG’s plans “The best looking plans in Land Development.”