WHY IS STORMWATER MANAGEMENT IMPORTANT?

Grandview Heights NCP Area 5a Presentation to CAC Members, Oct.20, 2009 By May Phang, P.Eng. – Drainage Planning Division, City of Surrey

The Hydrologic Cycle -Describes the continuous movement of water on, above, and below the surface of the earth.

-Precipitation (Rainfall) -Snowmelt -Runoff -Infiltration -Subsurface Flow -Evaporation -Transpiration -And many more processes…

WHAT HAPPENS TO RAIN WATER WHEN URBANIZATION AND DEVELOPMENT OCCUR?

DEVELOPMENT IMPACTS NATURAL PROCESSES EVAPOTRANSPIRATION EVAPOTRANSPIRATION

RUNOFF

RUNOFF INFILTRATION INFILTRATION

How Much Impact?

Zoning: ALR, Parks

Zoning: RA, RA-G, RH, RH-G

Zoning: RF-9, RF-12, Commercial, Industrial

How Do We Manage Storm Water Runoff? Methods such as: - Pipes - Storm Drains - Curbs and Gutters - Detention Ponds - Ditches and Creeks

Factors We Look At: 1) PEAK FLOW RATE: A higher peak flow rate requires larger and more expensive storm pipes and drains. Higher peak flow rates mean more frequent floods and more intense floods. 2) VOLUME: A larger volume means more energy that scour and erode creek beds leading to bank instability, increase sediment deposition in the lower reaches, and loss of habitat. 3) GROUNDWATER: If groundwater is not allowed to recharge, baseflows are reduced leading to longer, drier durations in ditches and streams. 4) WATER QUALITY: Poor management of runoff could result in increased contamination and pollution in our waters, impacting fish and wildlife.

WHAT HAPPENS WHEN WE DON’T MANAGE STORMWATER PROPERLY?

Flooding of Transportation Corridors

Damage to Properties

Erosion in streams and creeks

Pollution enters the drainage system

What We Are Trying To Protect

SO WHAT HAVE WE LEARNED ABOUT MANAGING STORMWATER?

Recognizing Goals For Better Design - Capturing and detaining stormwater runoff as close to the source as possible. - Reducing the volume of stormwater to minimize erosion. - Attenuate peak flow rates to reduce flooding. - Filtering stormwater to remove pollutants before the runoff enters groundwater, streams, or wetlands. - Using and promoting methods that provide multiple environmental benefits. - Using cost effective techniques in order to reduce life-cycle costs and environmental costs.

Sustainable Storm Water Management - To mimic nature by integrating storm water management into building and site developments to reduce the impacts that urbanization has on our natural resources. - Typical Best Management Practices (BMPs): - Increasing topsoil - Infiltration trenches - Porous pavement

- Typical Low Impact Development Concepts (LIDs): -

Cluster housing Bio-retention areas (rain gardens) Bio-swales Vegetation retention

EXAMPLE – Low Impact Development Site Plan Integrating LID concepts Site Plan Independent of LID concepts

Example Design – Large Lot

Implemented on this one lot: -Bio-swale -Rain Garden -Infiltration -Splash pads -Pervious deck -Pervious walkway -Cistern/Rain Storage -Vegetation Retention -Native shrub plantings

LIDs on Medium to High Density Lots

EXAMPLES

GREEN STREETS

DRAINAGE CORRIDORS

GREEN STREETS AND DRAINAGE CORRIDORS - Converts storm water from a waste directed into a pipe to a resource that replenishes groundwater supplies. - Provides attractive greenscapes and enhances neighbourhood livability while providing natural habitat and protecting water quality. - For severe events we still need to handle peak flows and protect people from flooding.

Benefits of green streets and drainage corridors: • Cleans and cools air and water • Enhances neighborhood livability • Increases community and property values • Enhances pedestrian and bicycle access and safety • Protects valuable surface and groundwater resources • Adds urban green space and wildlife habitat • Helps meet watershed management objectives

Examples

More Examples

WHAT DO WE WANT?

IN SUMMARY… - Storm water cannot be ignored! It doesn’t just go away! - We want the most value out of what we build. Multifunctional systems save money and land. - Need to provide properly designed BMPs and LIDs to manage impacts of storm water downstream. - There is liability associated with unmitigated downstream impacts.

THANK YOU QUESTIONS?