1. NHACC Annual Meeting 2014 New Approaches to Restoring NH’s Rivers Natural Channel Design and Dam Removal Peter J. Walker

2. “CROOKED STREAMS are a menace to life and crops in the areas bordering on their banks.”

6. NHACC 2014 Annual Meeting Stream Problems Past Channelization & Damming Watershed Changes – Imperviousness Hydro-modification – In-stream Flows Stormwater & Sediment Loading Lack of Riparian Buffers Floodplain Encroachment Barriers to Aquatic Organisms

7. NHACC 2014 Annual Meeting Fluvial Geomorphology Rosgen – Stream Classification Natural Channel Design Fluvial Erosion Hazard Mapping Watershed Approach Not just the stream, but the upland too Stream Solutions

8. NHACC 2014 Annual Meeting Fluvial Geomorphology Lane’s Relationship Schumm’s Channel Evolution Model Rosgen’s Stream Classification Stream Solutions

9. NHACC 2014 Annual Meeting

13. Uses of Stream Geomorphic Assessment Fluvial Erosion Hazard (FEH) Assessment – Land Use Management Approach Natural Channel Design – Restoration Measures to Address Instabilities

14. NHACC 2014 Annual Meeting FIRM vs. FEH

15. NHACC 2014 Annual Meeting Fluvial Erosion Hazard – Meander Belt Width

16. NHACC 2014 Annual Meeting Fluvial Erosion Hazard Zoning Resources Innovative Land Use Planning Techniques: A Handbook for Sustainable Development, Chapter 2.9 Shane Csiki, NH Geological Survey (NHDES) Model Ordinance

17. NHACC 2014 Annual Meeting Natural Channel Design – The Mission To return the stream to a natural state of dynamic equilibrium by: Stabilizing the banks and the bed of the stream. Optimizing the stream’s ability to transport and utilize its sediment effectively.

18. NHACC 2014 Annual Meeting What is a stable stream? Ability of the stream over time in the present climate to be able to transport flow and sediment in such a manner to maintain dimensions, pattern, slope, and profile with out aggrading or degrading. Must include the whole stream system. Still have scour and sediment transport.

19. NHACC 2014 Annual Meeting Natural Channel Design Structures Channel Stability Bank Stability Habitat Enhancement

21. NHACC 2014 Annual Meeting Stone Cross Vanes – Ashuelot River

22. NHACC 2014 Annual Meeting Natural Channel Design – Log Vanes

23. NHACC 2014 Annual Meeting Natural Channel Design – Log Vanes

24. NHACC 2014 Annual Meeting Natural Channel Design – Root Wad Revetment

25. NHACC 2014 Annual Meeting Natural Channel Design – Root Wad Revetment

26. National Inventory of Dams (NID) = 625 NID + Remaining Active Dams = 2,624 NID + Active + Inactive Dams = 4,549 Source: NH Dam Bureau Database Selective Dam Removal

27. NHACC 2014 Annual Meeting Why Remove Dams? Nationwide thousands of dams (large and small) are at or near the end of their useful, safe and economical life. Historically, dams were built with little, if any, consideration of their impact to the river system. We’ve learned:  Dams can be environmentally damaging  Free-flowing rivers play vital roles in ecosystem health  Growing public appreciation for rivers and desire to restore them

28. Dam DAM! Impoundment - Decreased Water Quality (decreased circulation) - Pollutants Accumulate (concentrate) - Oxygen Depletion (may become anoxic) - Reservoir Stratifies(loss of turbulent flow) Downstream - Water Quality is Reduced - Altered Flow Regime Original Riverbed Level Habitat/Substrate Buried by Sediment Free Flowing River at Dynamic Equilibrium epilimnion metalimnion hypolimnion Debris Jam Impounded Sediment Spawning Habitat - Traps Sediment - Traps Debris - Blocks Nutrient Transport - Algae Blooms - Blocks Fish Movement - Sediment Starved - Riverbed Degrades - Nutrient Starved - Increased Temperatures - Temperatures modified Slide by Laura Wildman, P.E.

29. NHACC 2014 Annual Meeting Photo Courtesy of VHB

30. NHACC 2014 Annual Meeting Homestead Dam Facts Timber Crib with Concrete Abutments Current Dam Built in 1910 (1860?) 1992-1993 Repairs 12 ft high X 167 feet long 1998 Inspection found deficiencies 2004 Inspection found significant concerns

31. Thompson Bridge Dam Sawyer Crossing/ Cresson Bridge Keene/Swanzey Boundary

32. NHACC 2014 Annual Meeting

39. Ecophotography Production

40. NHACC 2014 Annual Meeting NHDES Dam Removal and River Restoration Program Webpage

41. NHACC 2014 Annual Meeting Key Issues – Bid and Construction Pre-Qualify!!!!! (Then Low Bid) Well-planned and executed water diversion – Big Bid Item! Cross-Vanes are like a puzzle so take your time! Full-time construction observation with experienced inspector!

42. NHACC 2014 Annual Meeting Thank You! Pete Walker 391-3900 pwalker@vhb.com