Climate Change Implications for Stormwater Management in Massachusetts. Thomas Maguire, MassDEP March 2014

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1 Climate Change Implications for Stormwater Management in Massachusetts Thomas Maguire, MassDEP March 2014

2 Temperature ( o F) Boston, MA: Temperature Average Annual 1873 to 2013 R² = Avg: 51.7 o F Avg: 50.7 o F Avg: 49.4 o F Average Compiled from Boston WSFO and NCDC data

3 Precipitation Depth (inches/year) 70 Boston MA: Precipitation, Annual Depth R² = Avg: Avg: Annual Total and Averages Compiled from MassDCR and NCDC data

4 Precipitation Depth (inches/day) 8.00 Boston, MA: Precipitation, Annual Maxima Daily R² = Avg: Annual Maxima Series compiled from NCDC data

5 Number of Daily Storms/year 45 Boston, MA: Precipitation, Storms 1.5 in/day R² = Storms 1.5 Compiled from NCDC data

6 Precipitation (inches) 10.0 Boston, MA: Precipitation Return Period Frequency 1961 TP 40 versus 2011 Cornell NRCC % change TP NRCS-Cornell Cornell NRCC yr 24 hr 10 yr 24 hr 25 yr 24 hr 50 yr 24 hr 100 yr 24 hr Precipitation Return Period Frequency

7 , Massachusetts Peak Annual Maxima from USGS Gage # Data

8 , MA Temperate Climate Log Pearson Type III Analysis of USGS Gage # Data

9 Discharge (ft 3 /second) 40 Quaboag River near West Brimfield: Average Annual Minima Discharge R² = Annual Minima and Average compiled from USGS Gage # Daily Data

10 Mean Tide Data from NOAA Tide Station R 2 =0.9

11 Runoff Rate (feet 3 /second) 120 EFFECT ON RUNOFF RATE INCREASE IN FLOW RATE FROM 1961 EXISTING 2011 (Cornell NRCC) 60 HISTORIC 1961 (TP40) Return Period (years) Based on hypothetical 10-acre parking lot in East Boston location

12 Runoff Rate (feet 3 /second) PROJECTED ADDITIONAL INCREASE IN FLOW RATE PROJECTED 2050 EXISTING HISTORIC Return Period (years) Based on hypothetical 10-acre parking lot in East Boston location, with CLIMB projection of 0.31% precipitation increase each year

13 Runoff Rate (feet 3 /second) 120 PROJECTED EXISTING HISTORIC Return Period (years) Based on hypothetical 10-acre parking lot in East Boston location, with CLIMB projection of 0.31% precipitation increase each year

14 Runoff Rate (feet 3 /second) 120 PROJECTED EXISTING HISTORIC Return Period (years) Based on hypothetical 10-acre parking lot in East Boston location, with CLIMB projection of 0.31% precipitation increase each year

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16 Stormwater Management Implications Probable Cause More runoff - pipe capacity exceeded More runoff - pipe capacity exceeded More runoff - detention basin capacity exceeded Less snowpack melt/more runoff/higher ET Snow/Rain mix change in winter Elevated runoff temperatures Elevated temperature in stormwater treatment systems combined with greater time between storms in summer Collection and end-of-pipe Stormwater Treatment Systems in Floodplains (e.g. Detention Basins) Possible Effect CSO/SSO Discharge Frequency Increase Urban street flooding increase Upstream and downstream river flooding increase, increased scour to stream channels and stream culverts Less infiltration to groundwater seasonally: impact to drinking waters, wetlands, aquatic life Impacts to drinking water and aquatic life from increased salt use on roads Reduced cold water fishery Algae blooms & bio-magnification of pathogens in stormwater treatment systems, effect on downstream wetlands Reduced stormwater treatment on more frequent basis due to inundation from coastal and river flooding

17 Adaptation Current stormwater collection and treatment practices in Massachusetts are based on hydrology (TP40, published in 1961) Stormwater sizing methods currently in use rely on a design storm approach - static assumptions. Current actual as well as projected future hydrology for Massachusetts are greater than TP40. Low Impact Development and Environmentally Sensitive Site Design practices provide greater flexibility with lack of stationarity to reduce physical impacts to streams and wetlands, reduce impact to aquatic life, induce recharge, lag runoff, and provide stormwater treatment.