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

2. 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

3. 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

4. Sandy Gully, Kingston, Jamaica

5. Los Angeles River

6. Los Angeles River Proposed Restoration

7. 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

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

9. 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

10. 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

11. 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

13. 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

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

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

16. 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.

17. 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.

18. 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

19. Hydrological Cycle

20. 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

21. 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:

22. 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.