Re-plumbing Roadside Ditch Networks

Transcription

1 Re-plumbing Roadside Ditch Networks Ditches Improving management to reduce flooding, water pollution, and in-stream erosion and habitat degradation Rebecca Schneider Dept. Natural Resources Cornell University, NY PA Dirt and Gravel Roads Conference 27 September 2017

2 Watersheds determine the quantity and quality of water available Precipitation = Runoff + Groundwater + Evaporation/transpiration

3 Naturally dynamic stream flow patterns rain Runoff Groundwater contribution base flow Runoff - High flow Groundwater - Low flow

4 PRE-development POST-development Center for Watershed Protection 1995

5 Human activities have shifted the balance increase in frequency and magnitude of floods increase in stream dry out, water table decline POST-development stream height PRE-development time (hrs/days/weeks)

6 Roadside Drainage Networks What role do they play in: Floods? Droughts? Water pollution? Stream ecosystem health?

7 Roadside Ditch Team Faculty: D. Orr, Cornell Local Roads Program T. Walter, Dept. Biological and Environmental Engineering D. Buckley, P. Bergholz, Dept. Crops and Soils R. Marino, R. Howarth, K. Sparks, Dept. Ecology S. Allred (Dept. Natural Resources) Graduate Students: K. Falbo, B. Buchanan, J. Diaz-Robles, J. Archibald, L. McPhillips, S. Davis, W. Pluer, T. Johnson, J. Kimchi

8 Study Sites NY PA

9 Approaches (1) GPS and ARC-GIS MAPPING Ditch lengths Connections to streams Management types (2) MONITORING Total water flow Suspended sediment Dissolved chemicals Bedload Fecal coliforms

10 Ditch Study Sites vegetated exposed, scraped

11 Results - Drainage Mapping Characteristic Watershed area Road length Roadside ditch length* Total ditch length connected to strms Total # of direct connections to strms % road surface area of wtshd Area of basins draining to ditches % of watershed draining to ditches Stream channel length (no ditches) Stream channel density w/o ditches Stream channel density with ditches Average value 42.3 km 2 (16.3 sq. mi) 54.3 km 81.4 km* (50.6 miles) 51.0 km (31.7 miles) % 8.1 km 2 (3.1 sq. mi) 22.0 % 66.0 km 1.55 (km/km 2 ) 2.73 (km/km 2 ) * 23% is exposed scraped or eroded

12 Results Drainage Mapping Ditch drainage basins potentially intercept ~22 % of the surface runoff and shallow groundwater from each watershed and rapidly shunt it to the nearest stream. Ditch drainage basins Stream Road ditches Ditch outflows

13 Results Hydrology Doolittle Creek Watershed 8 ditch monitoring stations and Doolittle Crk 10 storms ; cm total rain/event Each ditch captured avg of 51% of rainfall in the ditch s basin Diaz-Robles 2007

14 Methods Hydrologic Model INPUTS: Slope Soils Land use Runoff Routing Methods Buchanan et al. 2012

15 Results Hydrologic Model Entire Modeled Ditch Drainage Networks: Doolittle: transported 45,400 m 3 water / storm = 3.6% (+/- 1.4%) of incoming precipitation and 19.5% (+/- 9.7%) of total stream flow measured in each storm Paine s Creek: 22% of total stream flow in spring storm event and 29% of total stream flow in a summer storm event.

16 Results - Hydrology 7 ditches 34 storms mm rain April Dec Paine s Creek Watershed Buchanan et al. 2012

17 Results Hydrology spring summer Ditch discharges contribute to increased peak flows (avg 78%) and total flows (avg 57%) in streams. Buchanan et al. 2012

18 Results: Ditches alter the Natural Flow Regime, Aka Environmental Flows Ditches stream height No ditches time (hrs/days/weeks)

19 Results Sediment 6.00E-03 Discharge ( TSS concentration Discharge 0.03 Ditches are a source of sediment and associated contaminants to downstream waters, especially when scraped. TSS concentration 5.00E E E E E (m^3/sec) Discharge (m3/sec) 0.00E Duration of storm (hrs) Diaz-Robles, 2007 Photo Bill Hecht

20 Results Nutrients, Cations A diversity of chemicals dissolved in the water and adsorbed on the sediment particles are transported by ditches downstream. Nutrients Trace Metals Cations Element Total load (kg) Ortho-Phosphates 1.43 Total P NO 3- + NO Al Mn 1.48 Fe Ni 6.39 Cu 1.28 Pb 0.25 Cr 3.79 Zn 2.90 Na + 11, Mg K Dissolved Chemical Loads over 10 storms De-icers Ca 2+ 3, Anions As Diaz-Robles 2007

21

22 Methods - Microbes E. coli quantification Idexx s Colilert/Quantitray Method Positive for Total Coliforms Manure spread on farm fields Positive for E. coli Falbo et al. 2012

23 Results - Microbes Manure spreading, livestock pasturing microbes move via tile drains to roadside ditches E. coli concentrations (MPN/100mL) Manure spreading Manure spreading 0 7/08 8/08 9/08 10/08 11/08 12/08 1/09 2/09 3/09 4/09 5/09 6/09 7/09 EPA STD

24 Results Bedload Large quantities of gravel, rocks and other bedload move out of ditches and form deltas in the streams.

25 Results Bedload + Discharge Stream Geomorphology Moose River, Adirondacks High velocity discharges, bedload deltas impact stream at ~94 locations in each watershed.

26 Results Hydraulic Radius and Substrate Average Bankfull Width (m) Upstream 30 m Ditch Width (m) Stream Number Upstream Downstream Average Grain Size Distribution Flow direction %Total Upstream Downstream 15 Downstream 30 m < Grain Size (mm) Kimchi 2010

27 Streams are in chronic disequilibrium with a stormdriven geomorphology upstream downstream

28 On-going Research: Conduits/ filters of Nitrogen from manure? NO 3 ~20 mg/l N 2 O ~50 ug/m 2 -hr Marino 2017 in prep Groundwater Exchange NO kg/ 6 mo

29 On-going Research: wood chip bioreactors to filter N? 2016 Will Pluer

30 Summary Roadside Ditch Impacts Intercept, capture and shunt ~20% of watershed runoff to streams Contribute to flooding in streams Contribute to headwater stream dry-outs and probably lowering of water table Rapid conduit, and source, of sediments, pathogens, de-icers and nutrients Contribute to in-stream erosion and stream ecosystem degradation

31 Extension Program on Re-plumbing Ditches Presentations to ~2,800 town highway staff Cornell Local Roads Highway School, Town govts Chesapeake Bay Watershed Conference and Report 2016

32 Re-plumb our watersheds to reduce floods, droughts and pollution Strategies to Reduce Flooding /Droughts Disconnect ditches from streams. Use infiltration basins, constructed wetlands, or detention ponds that allow for groundwater recharge. Catch and save the rain to buffer the impacts of climate change!

33 Strategies to Reduce Pollution Mow ditches, instead of scraping. Hydroseed immediately after ditching. Ditches as opportunity for a watershed-wide filtration system.

34 Questions?