Storm Water Management Norman W. Garrick CE 4410 Spring 2017 Lecture 9

In a natural environment, soil and plants absorb rain In a natural environment, soil and plants absorb rain. But when streets, buildings, and parking lots cover the ground, rain washes over these hard surfaces.  The resulting stormwater runoff carries dirt, oil and other pollutants to rivers and streams and can also cause erosion and flooding that harm properties and wildlife habitat. City of Portland, OR Green Infrastructure https://www.portlandoregon.gov/bes/34598 https://www.portlandoregon.gov/bes/34598

In the near past the philosophy of storm management was to move water off-site as quickly and efficiently as possible Little consideration was given to the downstream impact of this approach

Sandy Gully, Kingston, Jamaica

Los Angeles River

Los Angeles River Proposed Restoration

Portland uses green streets, eco-roofs, trees, and other green infrastructure to manage stormwater, protect water quality and improve watershed health. Urban streams, forests, and wetlands manage stormwater naturally and are part of Portland's green infrastructure. City of Portland, OR Green Infrastructure https://www.portlandoregon.gov/bes/34598

Quantity and Quality Effective stormwater management needs to consider both the Quantity and Quality of the runoff entering the natural drainage system

Quantity of Runoff Urban construction often results in smoother, more impervious surfaces which reduce the storage capacity of the land and increase the speed of stormwater run off. This increased volume AND rate of runoff can overwhelm existing drainage systems and results in a variety of problems including Flooding Decreased groundwater supply Increased soil erosion and sedimentation

Quality of Runoff Urban construction not only affect the volume and rate of run off but also results in degradation of the quality of the runoff in a number of ways. Some of the major issues include Petrochemical pollutants Winter sand and salts Sediments Herbicides, pesticides and fertilizers Organic matter (leaves, animal droppings that results in increase nutrient and bacterial loads) Higher water temperatures

Over one-third of Portland's 2,500 miles of sewer pipes are more than 80 years old. Green infrastructure protects the aging sewer system and makes it operate more efficiently by keeping stormwater out of sewers. City of Portland, OR Green Infrastructure https://www.portlandoregon.gov/bes/34598

Green infrastructure brings nature into the city, which can improve both mental and physical health, increase property value, conserve energy, enhance wildlife habitat and save money on more costly pipe infrastructure. City of Portland, OR Green Infrastructure https://www.portlandoregon.gov/bes/34598

Effective stormwater management requires more than just site/project based action but also action at the regional/watershed level

Stormwater Management Strategies Regional/watershed Stormwater Management Strategies Zone for compact, walkable development Eliminate minimum parking requirements in zoning codes

Case Study of Tippecanoe County, Indiana Parking Case Study of Tippecanoe County, Indiana Purdue University researchers found that parking spaces outnumbered drivers 3-to-1 and total parking area was larger than 1,000 football fields, covering more than two square miles. http://www.purdue.edu/uns/x/2007b/070911PijanowskiParking.html

Case Study of Tippecanoe County, Indiana Parking Case Study of Tippecanoe County, Indiana "The problem with parking lots is that they accumulate a lot of pollutants – oil, grease, heavy metals and sediment – that cannot be absorbed by the impervious surface," Engel said. "Rain then flushes these contaminants into rivers and lakes." Heavy metals accumulate on parking lots from car batteries and even from airborne fumes, a phenomenon called dry deposition. Also, since rainfall cannot penetrate parking lots, they generate large amounts of flowing water, worsening flooding and erosion – and water pollution, Engel said. Parking lots also help add to the "urban heat island effect," which can raise local temperatures 2 to 3 degrees Celsius, according to Indiana state climatologist Dev Niyogi. http://www.purdue.edu/uns/x/2007b/070911PijanowskiParking.html

Stormwater Management Strategies Site/Project Level Stormwater Management Strategies Modern storm water practices are evolving to better take advantage of natural processes to reduce the amount of runoff, reduce the rate of runoff and to reduce the amount of pollutants and other toxic shocks entering the natural drainage system Modern storm water practices draw inspiration from the hydrologic cycle

Hydrological Cycle

Stormwater Management Strategies Site/Project Level Stormwater Management Strategies Various site/project level stormwater management systems have been developed that use some combination of mechanism such as bioretainment, infiltration, and capture Some of the more well know approaches include Low Impact Development (LID) Best Management Practices (BMP) Light Imprint Design

Stormwater Management Strategies Site/Project Level Stormwater Management Strategies Low Impact Development and BMP focuses and site specific factors. The problem is that some of the measures used on an individual site might actually contribute to more sprawl and less walkable, less appealing places. For example, requiring rain gardens in front of every house lead to houses being further back from the road. In this case, walkability and urban compactness suffers. In other words, some LID practices may lead to more SPRAWL which defeats the stormwater management gains from the LID Light Imprint takes a more holistic approach than attempts to use solutions that integrate stormwater management with good placemaking and does not sacrifice one for the other. Here is a great article by Laurence Aurbach discussing these issues in more details: http://pedshed.net/?p=270

Stormwater Management Strategies Site/Project Level Stormwater Management Strategies The main phenomena that are employed in site design include Evapotranspiration Bioretainment Evaporation Detention Infiltration Capture These phenomena are used to reduce runoff volume and rate but some also contribute to treatment of water quality.