Urban Stormwater Management : Challenges and Opportunities. Darryl Dormuth, Ph.D. Water Resource Specialist Associated Engineering

Transcription

1 Urban Stormwater Management : Challenges and Opportunities Darryl Dormuth, Ph.D. Water Resource Specialist Associated Engineering 1

2 Outline Urbanization Urban Drainage Design Challenges to Urban Drainage Opportunities 2

3 Urbanization The percentage of the world s population that live in urban areas is constantly increasing. 3 Image from City-data.com

4 Urbanization Canada Canada 1961 Total Population 18,238,247 Population Trends Saskatchewan Saskatchewan 1961 Total Population 925,181 30% Urban Rural 57% 43% Urban Rural 70% Canada 2011 Total Population 33,476,688 Saskatchewan 2011 Total Population 1,033,381 20% 80% Urban Rural 34% 66% Urban Rural 4 Source: Statistics Canada. Rural population refers to persons living outside centres with a population of 1000 or greater and outside areas with 400 persons or more per square kilometre.

5 Urbanization As a consequence of the increasing urbanization of our population, there is the potential for more people (and their businesses and property) to be affected by localized flooding. 5

6 Urbanization Image by the United States Environmental Protection Agency 6

7 Urban Drainage Design Drainage from residential lots Images from City of Winnipeg 7

8 Urban Drainage Design Once the water drains from our lots, the storm sewer system conveys it to the nearest water body. Image from City of Moose Jaw Image from the US Environmental Protection Agency 8

9 Urban Drainage Design Engineering practices such as the Rational Method and Computer modelling are used to size the storm sewer system. Rational Method Hydraulic Modelling 9

10 Urban Drainage Design The storm sewer system is designed to handle runoff for fairly frequent events. Typically storms that occur once every five years to once every ten years. In the case of a 1-in-5 year event, this means there is a 20% probability in a given year that there will be a storm of sufficient size that the sewer will back up and water will remain on the ground for a period of time. 10

11 Urban Drainage Design The major (overland) drainage system is designed to handle storms that are larger than 1:5 to 1:10 events. Grading and curbing so that ponding occurs in desirable areas. Streets are graded and curbed to provide an overland flow path to the nearest drainage channel or natural water body. 11 Image from Blogspot.com

12 Challenges to Managing Urban Drainage Despite our best efforts to design drainage systems that protect the built environment we can t predict everything that will happen once the drainage system is in place. 12

13 Challenges to Managing Urban Drainage Design Post Development Landscaping Natural settling War of the High Ground among neighbours 13

14 Challenges to Managing Urban Drainage Design Post Development 14

15 Challenges to Managing Urban Drainage Design Post Development City of Ottumwa 15 Image from Wikipedia

16 Challenges for Managing Urban Drainage Re-zoning from the original plan Emerging water quality regulations Smaller communities find it difficult to develop and administer drainage standards. 16

17 Challenges for Managing Urban Drainage Once drainage systems are constructed and in place, they are seldom looked at again unless unexpected flooding occurs. Is there a way to be more pro-active and to look at post-development systems so that potential flooding events can be anticipated and mitigated? 17

18 Opportunities More GIS and remote sensing data readily available. Radarsat Constellation Google Street View of the Gallagher Centre 18

19 Opportunities More cost-effective sensor technologies. Low power Easily integrated into SCADA and Wi-Fi systems Image from the National Research Council Image from SonTek 19

20 Opportunities More sophisticated computer models have been developed that: Have better couplings between the minor and major systems. Are capable of modelling overland flow in two dimensions. 20

21 Opportunities 2-D flood modeling in urban areas. 21 Courtesy of Computational Hydraulics International

22 Opportunities 2-D flood modeling in urban areas. 22 Courtesy of Computational Hydraulics International

23 Opportunities 2-D flood modeling in urban areas. 23 Courtesy of Computational Hydraulics International

24 Opportunities Current System Conditions Advanced Computer Models Scenarios and Responses Flood Mitigation Strategies for Urban Areas 24

25 Opportunities Radar data available in real-time for tracking weather systems. 25

26 Opportunities Current System Conditions Advanced Computer Models Weather System Tracking Flood Forecasting and Response 26

27 Opportunities There will be a lot of effort initially required to assemble and process the data needed to perform these activities. However, once this is done a few times the process should become streamlined and take much less time to perform subsequent analyses. Recommend that municipalities, along with the province, work together on a couple of pilot projects. 27 Move forward on a priority basis.

28 Summary The percentage of the population that is living in urban areas is steadily growing even in Saskatchewan. Localized flooding has an increasing potential to affect more people. Post-development urban drainage systems can be quite different than the original design. 28

29 Summary There are technologies that can be utilized to better prepare us for flooding in urban areas. Resources required to initially implement these technologies could be large and it is recommended that municipalities, along with the province, work together on pilot projects. 29

30 Thank You 30 A picture of Regina taken by Chris Hatfield from the International Space Station on March 2, 2013

31 Challenges to Managing Urban Drainage Flood protection of the built environment Protection of the watershed 31

32 Challenges to Managing Urban Drainage Combined and Separate Storm Sewer Systems 32 Image from the City of Philadelphia

33 Challenges to Managing Urban Drainage Drainage Policies for the City of Regina RED ( ) Combined Sewer System and some separate systems for street runoff BLUE ( ) Storm street and roof runoff Domestic weeping tile drainage and domestic sewage BLACK (1965-present) Storm street runoff Domestic weeping tile drainage and domestic sewage *Roof runoff is discharged to the ground surface 33

34 Challenges to Managing Urban Drainage Stormwater runoff from the built environment remains one of the great challenges to modern water pollution control. U.S. National Research Council (2008) 34

35 Challenges to Managing Urban Drainage Green Roofs Low-Impact Development Technologies Infiltration Trenches Evapotranspiration Infiltration Photo from Wikipedia Runoff Permeable Pavement Cisterns and Rain Barrels Infiltration Infiltration + Evapotranspiration + Harvesting 35 Image from Lake County, Illinois

36 Here is where we ll start Image from NASA 36