Updating Salem’s Stormwater Master Plan Presentation to South Gateway Neighborhood Association October 10, 2019
Introductions Robert Chandler, PhD, PE Assistant Public Works Director Glenn Davis, PE, CFM Chief Development Engineer Robin Dalke, CFM Floodplain Program Manager Hans Hadley, PE, CFM WEST Consultants, Inc. 2
One cannot start with a river valley… “The Walhamette River from a Mountain” by Paul Kane, 1847 (Royal Ontario Museum, Toronto) 3
replace it with a major metropolitan area… Google earth (Imagery Date 12/13/2015) 4
…and not irrevocably alter how the landscape responds to rainfall. December 1964 (Photo Credit: Statesman Journal) 5
Happening…. Flooding => Historic/Future New development => Continuous Creeks & habitat impacts => Historic/Future Stormwater Master Plan => 2020 Battle Creek Park Master Plan => 2020 Plans, policies, procedures => Ongoing 6
Agenda How is the City involved in this basin? ➢ What we’re doing now – Examples ⚫ Community Rating System (CRS) ⚫ Floodplain Management ⚫ Stormwater Programs ➢ Battle Creek Basin Plan ⚫ Data & modeling methodology and results ⚫ Detention & other measures to reduce flood risks ➢ Questions/Discussion ➢ Next Steps 7
Floodplain/Stormwater ➢ Community Rating System (CRS) ⚫ 2008 – Class 8 (10% reduction) ⚫ 2009 – Class 7 (15%) ⚫ 2012 – Class 6 (20%) ⚫ 2016 – Class 5 (25%) – 1 of 3 Best in Oregon ⚫ 2020-21 – Class 3 Goal (35%) – Top 10 Nationwide ➢ Floodplain Stormwater 8
Floodplain/Stormwater Key Elements: ➢ Floodplain management plan 41 Action Items in 2018 Plan ⚫ • Preventive Activities (12) • Property Protection (5) • Natural Resource Protection (7) • Emergency Services Measures (8) • Structural Projects (3) • Public Information (6) 1 st Year Annual Review ⚫ • 23 items complete or on-going • 18 items remaining
Floodplain/Stormwater Stormwater Program ➢ Stormwater Management Plan ⚫ 66 Best Management Practices ➢ Operations and Maintenance ➢ Flood Warning System ➢ Development Codes/Standards ➢ Stormwater Master Plan 10
Stormwater Master Plan Flood Improvement Simulations Plans Assumptions/ Financial Policies Strategies Stormwater Master Plan 11
Assumptions/Policies ➢ Based on Existing Land Use Laws ⚫ Development rights within UGB ⚫ Plan does not establish new regulations ➢ Maximize Cost Effectiveness ⚫ Establishes total costs needed ⚫ Does not generate new revenue ➢ Minimize Flood Damage ⚫ Project prioritization ➢ Downstream Effects ⚫ Does not merely move problems downstream 12
Hydrologic Model
Model Calibration/Verification
January 2012 Storm Calibration (~ 100-yr 48-hr / ~50-yr 72-hr)
January 2012 Storm Calibration (~ 100-yr 48-hr / ~50-yr 72-hr)
Design Storm Development (Normalized to 1-inch depth) SCS Type 1A (24-hr) November 1996 (48-hr) January 2012 (72-hr) February 1996 (72-hr)
Storm Duration & Distribution Selection 24-hr = 5.1 inches 48-hr = 7.2 inches 72-hr = 8.6 inches
Existing Development Conditions 100-yr (48-hr) Storm
Existing Development Conditions 100-yr (48-hr) Storm
Existing Development Conditions 100-yr (48-hr) Storm
Full Build-out Assumptions • Based on land use classification in July 2015 Salem Area Comprehensive Plan • City’s green infrastructure requirements not considered (worst -case) • Existing impervious surface = 12%, Full build-out impervious surface = 21% • Between 14% and 19% increase in peak basin discharges Existing % Full Build-Out % Primary Subbasin Name Impervious Impervious Battle Creek (Upstream of I-5) 12 21 Jory Creek 5 14 Powell Creek 7 25 Scotch Creek 11 17 Waln Creek 31 42
Full Build-out Conditions 100-yr (48-hr) Storm
Full Build-out Conditions 100-yr (48-hr) Storm
Full Build-out Conditions 100-yr (48-hr) Storm
Project No. BA-BC2 Description: Project creates two large storage areas downstream of the Waln Creek-Battle Creek confluence and installs two floodgates to retain water before reentering Battle Creek. A combined 19.5 acres of floodplain grading is split into a 12 acre parcel north of Battle Creek and a 7.5 acre parcel south of Battle Creek. Cost Estimate = $3,140,000 Annual Maintenance = $15,900
Project No. BA-BC3 Description: The project includes approximately 1,000 linear feet of Battle Creek channel grading to increase the channel size and create overflow benches similar to Waln Creek just upstream of the Battle Creek confluence. Cost Estimate = $330,000 Annual Maintenance = $2,200
Project No. BA-BC4 Description: The project includes approximately 1,800 linear feet of Battle Creek channel grading to increase the channel size and create overflow benches similar to Waln Creek. Properties and easements will need to be acquired by the City to provide room for channel grading. Cost Estimate = $1,000,000 + Real Estate Costs Annual Maintenance = $2,900
Project No. BA-BC5 Description: The project includes approximately 1,300 linear feet of Battle Creek channel grading to increase the channel size and creates overflow benches similar to Waln Creek. Easements will need to be acquired by the City to provide room for channel grading. Cost Estimate = $290,000 + Real Estate Costs Annual Maintenance = $1,600
BA-BC2 + BA-BC3 + BA-BC4 + BA-BC5 100-yr (48-hr) Storm - Existing Development
BA-BC2 + BA-BC3 + BA-BC4 + BA-BC5 100-yr (48-hr) Storm - Existing Development
BA-BC2 + BA-BC3 + BA-BC4 + BA-BC5 100-yr (48-hr) Storm - Existing Development
BA-BC2 + BA-BC3 + BA-BC4 + BA-BC5 100-yr Full Build-out
BA-BC2 + BA-BC3 + BA-BC4 + BA-BC5 100-yr Full Build-out
BA-BC2 + BA-BC3 + BA-BC4 + BA-BC5 100-yr Full Build-out
Summary 1. Reducing risks of flooding is: In progress Expensive Requires tradeoffs Inexact 2. Stormwater master planning is: In progress Complex Long-term Inexact 3. Actions you can take are: Be informed Be involved Be prepared Have flood insurance 36
Thank You 37
Discussion 38
Further Information Glenn Davis, PE, CFM Robert Chandler, PhD, PE Chief Development Engineer Assistant Public Works Director gdavis@cityofsalem.net rchandler@cityofsalem.net Robin Dalke, CFM Floodplain Program Manager rdalke@cityofsalem.net City of Salem Public Works Office: 503-588-6211 Stormwater Master Planning Website [In Progress] https://www.cityofsalem.net/utilities/stormwater + click on “Stormwater” Battle Creek Park Master Planning Website https://www.cityofsalem.net/Pages/park-planning-and-development.aspx 39
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