Green Infrastructure Lab

Auburn University

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Stormwater temperature is an essential but overlooked aspect of the urban stormwater condition. As urbanization increases, the thermal regime (surface, air, and water) of the surrounding environment is altered. Heated stormwater runoff flows into receiving waters where it mixes and potentially increases the base temperature of surface water in lakes, streams, bays and estuaries.  Fish and other aquatic life in particular, are sensitive to thermal pollution.  Mobile Bay is home to Alabama's seafood industry and provides estuary service (a place to grow) for many fish, crustaceans and wildlife. The main stormwater outfall for downtown Mobile, AL flows directly into Mobile Bay. The temperature of stormwater runoff (first inch of flow) flowing over impervious surfaces in downtown Mobile has been recorded as high as 50oC (122oF) during the month of July.

 

Low impact development (LID) are stormwater control measures (SCMs) that utilize strategies to reduce the negative impact of stormwater runoff on receiving waters and watersheds. These strategies include pervious pavement and rain gardens. Pervious pavement materials have been used in place of an impervious paved surface to both reduce and potentially treat stormwater runoff. This construction technology is well known as an urban stormwater mitigation practice, but has not been adequately evaluated for thermal heat removal effectiveness. Rain gardens manage stormwater through bioretention. Sediment, nutrient, and pollutant removal occurs as runoff comes in contact with the soil, bacteria, and roots of shrubs or other vegetation within the rain garden. The ability of rain gardens to mitigate thermal

pollution in runoff has not been quantified. The objective of this research is to evaluate the ability of multiple pavement types (impervious concrete, pervious concrete, pervious brick pavers), and rain gardens in mitigating thermal pollution in stormwater runoff. Results from this project will be used to establish a baseline measurement of heat removal effectiveness of pervious paving and rain gardens when used alone or in combination (SCM Trains).

 

Microcosms have been designed and constructed to test the hypothesis that pervious pavement and rain gardens can mitigate thermal pollution in stormwater runoff individually or in combination. This research is conducted in the Green Infrastructure Laboratory at the Mike Hubbard Center for Advanced Science, Innovation and Commerce (CASIC) Building in the Auburn University Research Park, Auburn, AL. Here pavement cells receive simulated sun (infrared lamps), and rain (water sprinkler) events. Impervious pavement cells and turfgrass cells are used as controls. Data collected includes microcosm cell surface, internal cell temperature, and water temperature exiting cells. Multiple scenarios of these SMCs are tested. The importance of this research is that it has the potential to impact estuary conditions and receiving waters in Mobile Bay and beyond. Thermal pollution to receiving waters is an urban stormwater problem throughout the world that negatively impacts fish and wildlife habitat.

CVs

Charlene M. LeBleu, FASLA, AICP

Mark Dougherty

Amy Wright

Keith Rahn

Rui Wang

GALLERY

Mitigating Heat Transfer

From Impervious Surfaces to Stormwater Design Using Alternative Methods & Pavement Types

 

Stormwater temperature is an essential but overlooked aspect of the urban stormwater condition. As urbanization and build-out occurs, the thermal regime (surface, air, and water) of the surrounding environment is altered. Heated stormwater runoff flows into receiving waters where it mixes and potentially increases the base temperature of surface water in lakes, streams, bays and estuaries. The amount of heat transferred, and the degree of thermal pollution is of great importance for fisheries management and the ecological integrity of receiving waters. Fish and other aquatic life in particular are most sensitive to thermal pollution. (Galli, 1990) This video demonstrates controlled laboratory test to assess low impact development (LID) stormwater control measures as a way to reduce the negative impact of the thermal characteristics of stormwater runoff.  This project hypothesizes that pervious surfaces and rain gardens/bioretention can be used to mitigate ground level thermal loads in stormwater runoff. This research is important because very little has been published on the mitigation of thermal pollution using LID strategies. Data collected will help establish the role of pervious pavement and rain gardens/bioretention to mitigate thermal pollution in stormwater runoff to our nation’s receiving waters.

 

Contributors:

Keith Rhan, Assistant Professor, Building Science, College of Architecture, Design & Construction, Auburn University

Charlene LeBleu, Associate Professor, Landscape Architecture, College of Architecture, Design & Construction, Auburn University

Dr. Amy Wright, Associate Dean for Instruction & Professor of Horticulture, College of Agriculture, Auburn University

Dr. Mark Dougherty, Associate Professor, Biosystems Engineering, College of Engineering, Auburn University

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Email: greeninfralab@gmail.com

Phone Number: 334-844-0192

 

GREEN INFRASTRUCTURE LAB

559 DeVall Dr.

Lab RM 132

Auburn University, AL 36849