ENSC 202 – 2004 Impervious Cover Impacts of Impervious Cover Lecture 6 – ENSC 202

ENSC 202 – 2004 Impervious Cover Urban Sprawl Sprawl is dispersed, automobile-dependent development outside of compact urban and village centers along highways and in rural countryside.

ENSC 202 – 2004 Impervious Cover Sprawl & Impervious Cover Center for Watershed Protection 2003

ENSC 202 – 2004 Impervious Cover Sprawl and Water Quantity Higher highs/lower lows Intensification/flashiness Center for Watershed Protection (2003)

ENSC 202 – 2004 Impervious Cover Runoff as a function of Imperviousness Center for Watershed Protection (2003) after Schueler (1987)

ENSC 202 – 2004 Impervious Cover Stream Enlargement due to IC

ENSC 202 – 2004 Impervious Cover Fine Sediment Deposition due to IC

ENSC 202 – 2004 Impervious Cover Center for Watershed Protection (2003) Impacts of Deposited Sediments

ENSC 202 – 2004 Impervious Cover Center for Watershed Protection (2003) Impacts of Suspended Sediments

ENSC 202 – 2004 Impervious Cover Stormwater contains more than sediments State of Maine (1995) …note the wide ranges

ENSC 202 – 2004 Impervious Cover Pollutant concentrations differ by land use Burton and Pitt (2002) Stormwater Effects Handbook A measure of variance in the data.

ENSC 202 – 2004 Impervious Cover National Event Mean Concentrations Center for Watershed Protection (2003)

ENSC 202 – 2004 Impervious Cover The ‘Simple Method’ for calculating runoff loading from stormwater Step 1 – What portion of the ‘effective’ rainfall becomes runoff? Rv = (0.9 * IA) where Rv = runoff coefficient IA = impervious area (%) from Impacts of Impervious Cover on Aquatic Systems, p. 61 (CWP 2003)

ENSC 202 – 2004 Impervious Cover The ‘Simple Method’ for calculating runoff loading from stormwater Step 2 – How much total runoff is there in a typical year? R = P * P f * Rv where R = runoff (inches) P = precipitation (inches) Pf = fraction of rain events that produce runoff (~0.9) Rv = runoff coefficient (Step 1) Note unfortunate mix of English and Metric units!

ENSC 202 – 2004 Impervious Cover The ‘Simple Method’ for calculating runoff loading from stormwater Step 3 – How much total loading occurs due to this runoff? L = U * R * C * A where L = loading in lbs U = unit conversion = R = runoff (inches, Step 2) C = concentration (EMC, mg/L) A = area (acres) Can be modified for bacteria

ENSC 202 – 2004 Impervious Cover Loss of LWD due to IC

ENSC 202 – 2004 Impervious Cover Biotic Impacts of Impervious Area Center for Watershed Protection (2003) as noted.

ENSC 202 – 2004 Impervious Cover Sprawl, impervious area, & impairment Center for Watershed Protection 2003

ENSC 202 – 2004 Impervious Cover Impaired Rivers Burton and Pitt (2002) Stormwater Effects Handbook

ENSC 202 – 2004 Impervious Cover Impaired Lakes Burton and Pitt (2002) Stormwater Effects Handbook

ENSC 202 – 2004 Impervious Cover Imperviousness and habitat quality Variation within a watershed Percent watershed impervious cover Index of Biotic Integrity (IBI) Fairfax County (2001) in CWP (2003)

ENSC 202 – 2004 Impervious Cover Variation among watersheds Total watershed impervious cover Index of Biotic Integrity (IBI) Horner and May (1999) in CWP (2003)

ENSC 202 – 2004 Impervious Cover Measuring Impervious Cover Total versus Effective or Net IC Direct measurements Inferred measurements – from land use – from road density – from population

ENSC 202 – 2004 Impervious Cover Stormwater management matters

ENSC 202 – 2004 Impervious Cover Mission of the Vermont Water Resources Board “To ensure that rules which guide the management of Vermont's water resources and wetlands are adopted and (on appeal) are interpreted, by a citizen board which is independent of the Agency of Natural Resources (ANR).”

ENSC 202 – 2004 Impervious Cover The WRB Stormwater ‘Docket’ “The purpose of the Docket is to create a forum for discussing the technical issues related to developing clean up plans for waters of the state impaired by stormwater in Vermont.” “The intended outcome of the Docket is …[to summarize] technical information…and to …provide recommendations for developing clean up plans for Vermont’s stormwater impaired waters…”

ENSC 202 – 2004 Impervious Cover Key Questions in the WRB Docket Is it feasible to use ‘source control’ as a primary option? Can improvements be achieved in 5 years? Can we separate and deal with natural vs man-made sources of pollutants? Is a TMDL approach the best way to address clean up streams impaired by stormwater? Are stormwater ‘offsets’ a reasonable approach to stormwater management? Can we predict how ‘indicators’ of impairment will respond to stormwater treatment strategies? What is the best way to evaluate progress toward desired goals? What are the best ‘targets’ to judge when we have attained desirable goals? If we can’t attain the standards we want, what should we do?

ENSC 202 – 2004 Impervious Cover Extra

ENSC 202 – 2004 Impervious Cover Redesigning the American Neighborhood Developing an Ecological & Socioeconomic Framework for Effective Stormwater Management Purpose: To develop tools that will allow stakeholders, regulators, and researchers to visualize alternative future environmental states that they imagine collectively and then to optimize the mix of interventions at various scales, that will best balance environmental and social, as well as economic, criteria.

ENSC 202 – 2004 Impervious Cover Why focus on scale? Effectiveness: uncertain Orientation: local protection Cost: known - medium Risk: uncertain - medium Effectiveness: unknown Orientation: source control Cost: uncertain – low? Risk: unknown – medium/high Effectiveness: known – depends Orientation: downstream protection Cost: known - high Risk: known - low

ENSC 202 – 2004 Impervious Cover Why focus on scale? Clearly, a mix of interventions is desirable. But what mix? For what purpose? Located where?

ENSC 202 – 2004 Impervious Cover Primary Goal Quantify the balances among environmental, economic, and social costs and benefits for storm water management at whole-watershed, neighborhood, and individual house scales in a typical New England landscape and climate.

ENSC 202 – 2004 Impervious Cover Key Objectives Assessment: What are the opportunities for intervention? Evaluation: What are the comparative cost/benefits of these interventions? Participation: How can we better involve community stakeholders to devise successful solutions? Implementation: Can we demonstrate the these approaches work?

ENSC 202 – 2004 Impervious Cover Project Focus Area

ENSC 202 – 2004 Impervious Cover Butler Farm Subdivision

ENSC 202 – 2004 Impervious Cover Key Collaborations US-EPA/SNR-UVM (McIntosh, Bowden, Todd, Voinov) Partnership with South Burlington (JB Hoover) Collaboration with key consultants (PEC, J Nelson) Advice from key stakeholders (Project Working Groups) EPA Demonstration grant (JB Hoover) NRCD implementation grant (A. Willard, B. Gabos)

ENSC 202 – 2004 Impervious Cover National and Vermont Standards Comparison to selected VT Water Quality Standards No TSS causing impairment – mg/L total phosphorus 2 and 5 mg/l nitrate for Class A and B waters 10 ug/L acute, 8 ug/L chronic* 23 ug/L acute, <1 ug/L chronic* 57 ug/L acute, 52 ug/L chronic* <<1 mg/L as pesticides and PCB’s No oil or grease causing impairment 18 E. coli cfu/100ml 3x in 30days (A1 and A2) 33 E. coli cfu/100ml once (A1 and A2) 77 E. coli cfu/100 ml (B) at hardness of 50 mg/L VT Stormwater Manual, Vol 2 VT Water Quality Standards