Joint Presentation with Josh Roe from the Kansas Department of Agriculture at the Kansas Natural Resources Conference on January 31, 2014. An evaluation of the effectiveness of streambank stabilization projects within the Tuttle Creek Lake near Manhattan, KS and the impacts addressing these sites can have on the local regional economy.

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.