research project details
Project Title: Data Set Acquisition to Model Storm Water Runoff
Investigator(s): David Beattie
Sponsor: U.S. Environmental Protection Agency
Research project summarized by student intern Ruth Gilbert
Environmental Problem Addressed:
Increased storm water runoff due to impervious surfaces and its associated impact on watersheds.
Research Project Objectives:
Acquisition of information needed to evaluate the effectiveness of green roofs in retaining and detaining storm water runoff. This includes determining which plants to use and the makeup of engineered soil.
Summary:
As North America becomes more developed, increasingly large areas of land are being covered with impervious surfaces such as buildings, roads, and parking lots. When storms occur, runoff from these impervious surfaces can impose a significant threat to water quality both locally and regionally. Green roof technology is a method that can be applied to reduce storm runoff.
Green roofs are thin plantings on the roof of a building, which are used to reduce roof runoff and watershed damage by retaining water after a rain storm. There are myriad benefits to the installation of green roofs. They not only retain water thereby reducing storm water runoff they also:
- Are aesthetically pleasing;
- Reduce city "heat island" effect;
- Reduce carbon dioxide impacts;
- Reduce summer air conditioning costs;
- Reduce winter heat demand;
- Lengthen roof life two to three times;
- Remove nitrogen pollution deposited in precipitation;
- Neutralize acid rain effects;
- Reduce noise; and
- Provide songbird habitat.
Germany has developed extensive green roof technologies. Industry figures suggest that approximately 10% of all roofs in Germany are greened and between 1989 and 1999, German roofing companies installed almost 550 million square feet of green roofs. Although green roofing methods have been developed and put into practice in Germany, there is little information available in English. Also, there is no infrastructure within the U.S. to provide materials, plants, and high quality blended media. Therefore, data must be acquired before the United States can effectively put green roofs into place.
Methods:
The Center for Green Roof Research at the Russell Larson Research Center has six buildings that will be used for tests: three will have green roofs with Sedum album and Delosperma planted in a clay-based medium composed of 85% mineral and 15% organic matter; two control roofs will be covered in rolled, black asphalt. The last roof will be used to retain and release water at a controlled rate using a catch basin water storage/retention system. All buildings are instrumented to determine detention and retention characteristics and runoff data will be collected continuously for all rain events and inter event intervals. Runoff quality of the green and asphalt roofs obtained from grab samples will be compared by examining pH, turbidity, total suspended solids (TSS), and nitrogen content.
To improve the reliability and precision of data model development, a series of tests will be conducted under controlled conditions in the Penn State Horticulture greenhouses. Beds with and without plants will receive simulated rainfall. The results from these simulated rainfall trials will provide water storage and retention and detention characteristics of the soil media. Rehydration, evapotranspiration, and plant growth rates under controlled environmental conditions of temperature, light, and vapor pressure deficit will be determined.