Hydromodification: a What, Why and How. A presentation to the KYTC - PowerPoint PPT Presentation

Hydromodification: a What, Why and How. A presentation to the KYTC Annual Partnering Conference September 9, 2014 Louisville, KY Matt Wooten, M.S. Aquatic Biologist, Sanitation District No. 1 (SD1) Bob Hawley, PhD, PE Principal Scientist, Sustainable Streams, LLC

Outline • Background • Monitoring • Hydromodification • Approach • Examples

Sanitation District No. 1 (SD1) Wastewater Utility • 31 cities and 3 counties • 176 square mile service area • 1700 miles of sewer • 130 pump stations • 3 Treatment Plans Storm Water Utility • 30 cities and 3 counties • 223 square mile service area • 400 miles of storm lines • 30,000 structures

Why do we manage storm water runoff ?

Why do we care about storm water runoff? • Flooding

Why do we care about storm water runoff? • Erosion • Infrastructure impacts • Excess sedimentation • Poor water quality, habitat loss, & biological degradation

What is Hydromodification? Activities that: • disturb natural flow patterns • alter stream geometry and physical characteristics • erode stream banks • can cause excess sedimentation Hydromodification is one of the leading causes of impairments in streams… EPA, 2007 …In the case of a stream channel, water…typically causing sedimentation.

Stream Assessment Program • ~75 sites: • Water Quality • Biology • Physical Habitat • Stream Stability (Hydromod)

Field Monitoring Program Revealed Significant Stream Degradation

70 ft Banklick Creek (N.KY) 2006 Aerial from SD1

Field Monitoring Program Revealed Significant Stream Degradation

Field Monitoring Program Revealed Significant Stream Degradation Even Concrete Walls Can Fail if Streams Continue Downcutting

Pre-failure

Bank Failure

Repair ~ $250,000 cost to fix

Why Is Hydromodification So Prevalent? Boone County - 1995

Change in Land Cover Impacts Hydrologic Cycle Boone County - 2007 315-acre development Estimated impervious surface: 190 acres Estimated increase in annual runoff volume: 103 million gallons

Sand Run

0.3” of rain in 1 hour

How Sensitive are the Systems to Improperly Managed Storm Water? Rain Event – 11/16/10 Magnitude – 0.45” Duration – 2 hours < 2-month storm (2-hour/2-month = 0.81”) ~100-acre basin

Undeveloped vs. Developed Watersheds Middle Creek (3.3 mi 2 ) Owl Creek (3.7 mi 2 ) Undeveloped (0.6% Impervious) Developing (9% Impervious)

Undeveloped vs. Developed Watersheds Owl Creek Middle Creek 103 102 101 100 Elevation (ft) 99 ~3’ 98 97 96 95 ~9’ 94 93 92 91 90 0 10 20 30 40 50 60 70 80 Station (ft)

Conceptual Framework of Channel Protection Controls Channel erosion likely begins in a range that is less than the 2-yr design storm Peak flow detention that focuses on the 2-yr storm has little to no attenuating effect on 97-99% of precipitation volume in a typical year ( Emerson et al., 2003, In Proceedings of ASCE’s Water and Environment Resources Congress) Typical year rainfall and recurrence probabilities for Northern Kentucky

Introduction of Q critical The Critical Flow (Q critical ) for Bed Material Mobility is both Geomorphically and Ecologically Relevant (Poff, 1992; Townsend et al., 1997; Holomuzki and Biggs, 2000; Suren and Jowett, 2006) t > t c

Example of Flow Control for Channel Protection from Bledsoe (2002) Analysis of the 2-yr, 2-hr storm from Fort Collins, CO by Bledsoe (2002), Journal of Water Resources Planning and Management

Example of Flow Control for Channel Protection from Bledsoe (2002) Analysis of the 2-yr, 2-hr storm from Fort Collins, CO by Bledsoe (2002), Journal of Water Resources Planning and Management

Example of Flow Control for Channel Protection from Bledsoe (2002) Analysis of the 2-yr, 2-hr storm from Fort Collins, CO by Bledsoe (2002), Journal of Water Resources Planning and Management

Frequency of Q critical in Developed vs. Undeveloped Conditions (developed land cover with no detention) Predeveloped: Pleasant Run 50-year Simulation 10000 Q critical exceeded • Existing (no detention) Existing Q critical = 20 cfs Hours Exceeding Q critical : 1 hour every 2 Pre-Developed Existing (no detention) 275 hrs 1000 years Pre-developed 25 hrs Excess 250 hrs ( + 1,000% ) 100 Duration (hours) Developed: 10 Q critical exceeded • 1 hour every 2 1 months 0.1 0.01 3 8 13 18 23 28 33 38 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215 225 235 245 255 265 275 Flow (cfs) Hawley et al. (2012)

Preferred Approach Focuses on All Flows > Q critical Match the Pleasant Run 50-year Simulation 10000 Cumulative Qcritical Detention Proposed Q critical = 20 cfs Duration and Hours Exceeding Q critical : Pre-Developed Q critical detention 13 hrs 1000 Erosion Potential of Pre-developed 25 hrs Excess -12 hrs those Flows that ( - 50% ) 100 Duration (hours) Exceed Q critical (to the extent possible/practical) 10 1 0.1 0.01 3 8 13 18 23 28 33 38 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215 225 235 245 255 265 275 Flow (cfs) Adapted from Hawley et al. (2012)

What is the connection? Biological Physiochemical Geomorphology Hydraulics Hydrologic Stream Function Pyramid (CWP)

Shorter Riffles Deeper and Longer Pools DRC 1.0 Profiles 2008 2009 2011 27 Survey Pool Riffle Pool/Riffle Maximum Date Length (m) Length (m) Ratio Pool Depth (m) 7/18/08 61.3 9.7 6.3 0.52 7/28/09 68.1 6.4 10.6 0.48 7/27/11 68.8 1.2 59.7 1.05 26 Elevation (m) 25 24 23 0 25 50 75 100 125 Station (m) Hawley et al., Geomorphology, July 2013

Shorter Riffles Deeper and Longer Pools Hawley et al., Geomorphology, July 2013 Hawley et al., Geomorphology, July 2013

Findings of Stream Monitoring Effort Channel Enlargement Lodor’s Creek Imperviousness causes: 31.0 • Channel Enlargement 30.5 • Bed Coarsening Top of Bank • Shorter Riffles 30.0 Elevation (m) • Bankfull Longer/Deeper Pools Elevation 29.5 • Stream Instability 2010 29.0 2011 28.5 28.0 p ≤ .05 except for bed 0 5 10 15 20 25 coarsening ( p = 0.15) Station (m) Hawley et al., Geomorphology, July 2013

Similar Trends with Hydromodification as measured by stream stability 160 10 SI = -1.41ln(Imp) + 1.99 R² = 0.30 140 p = 0.03 8 (Calibration Sites) Habitat Score 120 Stability Index 6 100 4 80 HS = 4.22 SI + 91.9 R² = 0.26 2 60 p<0.0001 40 0 0 2 4 6 8 10 1% 10% 100% Stability Index Watershed Imperviousness (Validation Sites)

Bed Coarsening 2008 2010 Site: BLC 8.1 2011 100% Survey d50 Date (mm) 11/4/08 56.7 5/18/10 119.6 Percent Passing 8/2/11 90.0 50% 0% 1 10 100 1000 Diameter (mm) Hawley et al., Geomorphology, July 2013

Biological Survey Findings Biological integrity decreases with watershed imperviousness: • Overall Taxa Richness • Sensitive Taxa (EPT) Richness • Macroinvertebrate Biotic Index • Community Structure 25 60 70 60 20 50 50 15 40 EPT_G G_TR MBI 40 10 30 30 5 20 20 0 10 10 0 10 20 30 40 0 10 20 30 40 0 10 20 30 40 PERC_IMP PERC_IMP PERC_IMP (Wooten and Hawley, In prep) p<0.01 for each

What are the Overall Impacts? Decreased biotic integrity, Biological dominance of ‘weedy’ species Physiochemical Increased Suspended Solids and Sedimentation Geomorphology More homogeneous & unstable habitat Hydraulics More frequent, severe, & prolonged Hydrologic disturbance events Conventional Stormwater Controls / Hydromodification Stream Function Pyramid (Adapted from Harmon et al., 2012 )

So, How Do We Implement? • New Roads • Resurfacing/Widening • Urban Corridors

Case Studies • Watershed Scale – Dry Creek Concept Plan • Project Scale – Road extension

Dry Creek • 12.4 square miles • 30% impervious

Condition of Dry Creek • Storm water runoff: – Pre-development: ~1.8 billion gallons – Post-development: ~3.4 billion gallons • Monitoring at 4 sites – Rapid downcutting – Severe bank erosion

Stream Bank Failure SITE 4: DRC 1.0 SITE 3: • Geotechnical instability DRC 4.4 – Failure by its own weight SITE 1: SITE 2: WFD 1.5 DRC 5.9

Bank Failure Likely to Continue • Active incision and weathering of bedrock • Continued incision  more bank instability