Streambank Stabilization Effectiveness and the Effect of Streambank Erosion on Regional Economy

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Information about Streambank Stabilization Effectiveness and the Effect of Streambank...

Published on November 13, 2017

Author: MattUnruh1

Source: slideshare.net

1. Streambank Stabilization Effectiveness and the Effect of Streambank Erosion on Regional Economy Kansas Natural Resources Conference January 31, 2014 Wichita, KS Matt Unruh – Kansas Water Office & Josh Roe – Kansas Dept. of Agriculture

2. What’s Sediment Source? • Streambank Aerial Photo Assessment – Tells us the portion of the mean annual sediment load coming from actively eroding SB in watershed • The remainder is assumed to come from land surface sources

3. Failing Streambank Hotspots

4. Typical Streambank Stabilization Project Concerns • SB stabilization projects don’t have a track record to establish their effectiveness – They fail – If they don’t fail, then they certainly don’t perform as well as advertised – They cause an increase to erosion immediately downstream of the project • Some projects have been in place on the Little Blue River for more than a decade – How have they performed?

5. Site 1 : Stateline

6. Soil Loss • 1991 – 2002 – Surface Area = 600,000 ft2 (13.8 acres) – SB Height = 17 ft – Soil Mass = 433,500 Tons • Little Blue R. alluvial soil bulk density = 85 lbs/ft3 – Reservoir Storage Loss = 407 AF • Sediment bulk density = 45 lbs/ft3 • Reservoir Trapping Efficiency = 92%

7. Dredging Cost Comparison • 407 AF of sediment = 656,500 yds3 • $4.37 Million to dredge – $6.66/yds3 dredge cost • SB Stabilization Cost = $210,000 – Design $20,000 – Installation $190,000 – C/B = $210,000/$4,370,000 = 1:21 • Dredge Benefit

8. Site 2 : B. Blue US L. Blue Confluence

9. Soil Loss Stabilized 1991-2005 2005-2012 Surface Area (AC) | SB Hgt (ft) 7.2 Ac | 17.4 ft 0.0 Ac | 17.4 ft Mass (Tons) 232,000 T 0 T Reservoir Stor Loss (af) 218 AF 0 AF Dredge Removal Cost ($) $2.3 M $ 0 M Install Cost ($) - Today $183,000 $0 Non-Stabilized (DS Site) 1991-2005 2005-2012 Surface Area (AC) | SB Hgt (ft) 5.9 Ac | 21.7 ft 2.0 Ac | 21.7 ft Mass (Tons) 490,000 T 79,000 T Reservoir Stor Loss (af) 222 AF 74 AF Dredge Removal Cost ($) $2.4 M $ 0.8 M Install Cost ($) - Today $223,000 $223,000 Erosion Rt 5.9/14= 0.42 ac/yr I 2.0/7 = 0.29 ac/yr

10. Site 3 : WS/MS Line

11. Soil Loss Stabilized 1991-2002 2002-2012 Surface Area (AC) | SB Hgt (ft) 10.8 Ac | 20.5 ft 0 Ac | 20.5 ft Mass (Tons) 410,00 T 0 T Reservoir Stor Loss (af) 385 AF 0 AF Dredge Removal Cost ($) $4.1 M $0 M Install Cost ($) - Today $174,000 $0 Non-stabilized (US Site) 1991-2002 2002-2012 Surface Area (AC) | SB Hgt (ft) 5.8 Ac | 20.5 ft 4.4 Ac | 20.5 ft Mass (Tons) 220,000 T 170,000 T Reservoir Stor Loss (af) 205 AF 155 AF Dredge Removal Cost ($) $2.2 M $1.7 M Install Cost ($) - Today $133,000 $133,000

12. Overall Impact 1991-2008 SB Cropland Sites Cropland Loss (acres) Streambank Stabilization Installation Cost Annual Dredge Cost Dredge Volume (af) 146 595 $23,255,680 $13,152,128 1,225 $23 Million : $224 Million = 1:10 Dredge Benefit Recall first site (at Stateline) had 1:21 Dredge Benefit

13. Summary/Next Steps • Streambank stabilization has excellent returns when compared to dredging costs • Streambank stabilization does have some regional economic benefit – What’s the impact of losing cropland acres to bank erosion?

14. Regional Economic Impacts • Acres lost to streambank erosion has direct income and net worth impacts to producer. • The regional economy (input suppliers, banks, insurance, and local business) also affected. • Streambank stabilization is expensive.

15. Types of Impact • Direct: Change in crop production. • Indirect: Changes in local spending from input suppliers. • Induced: Changes in household spending from both the direct and indirect impacts. • IMPLAN software utilizes local economy trade patterns to estimate these effects.

16. Three Sites Site Acres Land Value Total Impact (Annual) Installation Cost Benefit less installation (20 Year) 1 13.8 $69,000 $13,281 $210,000 $124,618 2 6.7 $33,500 $6,448 $182,000 -$19,540 3 8.3 $41,500 $7,988 $130,000 $71,256 • Corn and Soybean rotation • Expected 2013 market prices and typical yields • Land Value: $5,000/Acre • Impact multiplier 1.245

17. All Sites Site Acres Land Value Total Impact (20 Years) Installation Cost Benefit less installation (20 Year) 146 Sites (All) 595 $2,975,000 $12,077,893 $23,255,680 -$8,202,787 73 Sites (Top 50%) 497 $2,485,000 $10,088,593 $14,556,260 -$1,982,667 19 Sites (Top 13%) 183.5 $917,450 $3,724,660 $3,547,844 $1,094,266

18. 0 5,000,000 10,000,000 15,000,000 20,000,000 25,000,000 30,000,000 35,000,000 -$10,000,000 -$5,000,000 $0 $5,000,000 $10,000,000 $15,000,000 $20,000,000 $25,000,000 0 20 40 60 80 100 120 140 160 SoilLoss(Tons) Benefit/Cost($) Sites (#) Total Benefit Stabilization Cost Net Benefit Soil Mass Loss

19. Graphically 0 5,000,000 10,000,000 15,000,000 20,000,000 25,000,000 30,000,000 35,000,000 -$10,000,000 -$5,000,000 $0 $5,000,000 $10,000,000 $15,000,000 $20,000,000 $25,000,000 0 20 40 60 80 100 120 140 160 SoilLoss(Tons) Benefit/Cost($) Sites (#) Total Benefit Stabilization Cost Net Benefit Soil Mass Loss 1 Maximizes economic benefit (10%) 2 Maximizes environmental benefit with no economic penalty (38%) 3 Dual optimal solution with goal of maximizing economic benefit and environmental benefit (30%) 1 2 3

20. Summary/Next Steps • Erosion rate affects net impact. • Reservoir loss not factored into economic impact (dredging costs). • Streambank stabilization treated as a cost, does have some regional economic benefit.

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