Integration Of Stormwater Master Plans with Watershed Plans The Link between Flooding and Development September 23, 2008 Bob Murdock, P.E., CFM

The Nexus of Watershed Planning with Stormwater Management  The interconnection of flood management actions within broader water resources management and land use planning;  The value of coordinating across geographic and agency boundaries  The need to evaluate opportunities and potential impacts from a system perspective  The importance of environmental stewardship and sustainability. Why consider the watershed within our stormwater planning? Specific Benefits:

 Floods  Water Quality  Environment - Quality of Life Why consider the watershed within our stormwater planning? Central Message: What you do in one part of the watershed affects the rest…..stormwater management and development

s 1980s 1970s 1960s 1950s 1940s 1930s 1920s 1910s BILLIONS (adjusted to 1999 dollars) Trends in Flood Damages  $6 billion annually  Four-fold increase from early 1900s  Per Capita Damages increased by more than a factor of 2.5 in the previous century in real dollar terms $ $ 2.2 $ $ 2.0 $ $ 2.9 $ $ 2.4 $ $ 3.4 $ $ 2.2 $ $ 4.9 $ $ 3.3 $ $ 5.6

Demographic Trends: The Future  As We Move Into the Next Generation Things Will Be Much More Challenging For Floodplain and Stormwater Managers  Dr. Arthur “Chris” Nelson, FAICP  Leadership in a New Era  “More than half of the built environment of the United States we will see in 2025 did not exist in 2000” Journal of the American Planning Association, Vol. 72, No. 4, Autumn 2006 © American Planning Association, Chicago, IL

As printed in

USA Today April 29, 2008  Chris Nelson Tells APA Convention That:  In the Next One Hundred Years the US Population Will Grow To:  Any Guesses?

So consider….. Even if we perfectly implement current standards, damages and flood heights will increase Remember, we have done a number of positive things, both non-structural and structural, but… We’ll discuss why that is…

Components of Impervious Cover in the Urban Landscape Roads Parking Buildings Sidewalks Driveways Center for Watershed Protection 6

Agriculture Undeveloped Existing Development 1940s Undeveloped 7 Center for Watershed Protection

Agriculture Undeveloped Existing Development 1950s Undeveloped 8 Center for Watershed Protection

Agriculture Undeveloped Existing Development 1960s Undeveloped 9 Center for Watershed Protection

Agriculture Existing Development 1970s Developed 10 Center for Watershed Protection

Existing Development 1990s Under Construction Developed Center for Watershed Protection 11

10%40% 25% Good Fair Poor Watershed Impervious Cover Stream Quality 60% 100% Sensitive Impacted Non-Supporting Impervious Cover Model Urban Drainage

10% IC

30% IC 18

IC and Stream Habitat % 20 20% 30% > 65% < 5%

Questions for your Plan Development What kind of practices do you want consider and encourage within your master plan and ordinance, given what we know about impervious cover and its effect on watershed health? 1 st - Conservation

Existing Commercial Existing Low Density Residential Existing Medium Density Residential Currently Zoned Medium Density Residential Propose changing zoning to Residential Cluster Development 58

Photo Copyright 1999, Center for Watershed Protection

Buffer Width

Questions for your Ordinance Development What kind of practices do you want consider and encourage within your master plan and ordinance, given what we know about impervious cover and its effect on watershed health? 2 nd : Site Specific Low Impact Development

Cul-de-Sacs Not so good. Good. 72

Street Width Not so good. Good. 73

Not so good. Good. Conventional Subdivision Open Space Subdivision

Parking lots are often underutilized and can be minimized through better site design techniques. Copyright 2000, Center for Watershed Protection

3 rd: For the Engineering Geeks Central Message  Your ordinance actions do affect others in the watershed

Hydrographs for Pre and Post Development Conditions Source: California State Water Resources Control Board Stormwater Program And The Water Board Academy, 2007 Q

Post-Development with Conventional Detention Source: California State Water Resources Control Board Stormwater Program And The Water Board Academy, 2007 Traditional Stormwater Detention Practice Q

Watershed with Combined Flows at Tributaries Source: Georgia Stormwater Manual, 2001

Volume Effects at Downstream Tributaries Source: Georgia Stormwater Manual, 2001 QQ

Q Post-development hydrograph response to LID controls Source: California State Water Resources Control Board Stormwater Program And The Water Board Academy, 2007

Establish Hydromodification Management Plans (HMPs)  HMPs are now a requirement of various regional regulatory programs including:  San Francisco Bay Area (discharge rates and flow durations maintained from 0.1 x Q2yr to Q10yr; erosion potential evaluation)  San Diego County (Permit requires LID measures and HMPs)  New Jersey (requires 100% of pre-construction groundwater recharge, and HMPs for various events)  Portland (incentives for green infrastructure, reduced utility rates for green onsite stormwater management)  Washington DC – Anacostia River (On-site retention of 1-in rainfall and Wtr Qual treatment for 2-yr storm)

Some Closing Points:  No Watershed Study – No Big Deal  Reach out to other communities and watershed organizations  EPA and other agencies do offer grants for watershed studies  Remember – A community’s stormwater actions affects the entire watershed, so ask if the actions will make a difference….

Integration Of Stormwater Master Plans with Watershed Plans QUESTIONS? Bob Murdock, P.E., CFM