A Review of WaveInduced Resiliency
Studies
Presented by: William Miller, Ph.D., P.E.
June 2015
PRESENTATION OUTLINE
1. Motivation
2. Purpose of Review
3. Formulating the Problem
4. Review of Testing/Literature
5. Summary
2
MOTIVATION
• Existing grass-covered clay & sand levee
enclosing reservoir
• Rezoning area around levee  residential
• Increase the hazard rating  increased
design storm strength (state requirements)
• Freeboard still exceeded storm SWL, but
not wave runup
3
WAVE RUNUP & FREEBOARD
• New wave runup exceeded existing freeboard
• Not sufficient footprint to raise freeboard
enough
waves break
freeboard
runup
SWL
Levee
4
REDUCE WAVE RUNUP
• Elaborate modifications to levee to meet
freeboard requirements for wave runup

e.g. riprap
SWL
Levee
5
PROBLEM
• Setting the freeboard above the maximum
possible wave runup (or measures to
reduce runup)
Result in significantly higher costs
 Small return on investment:
o Avoid conditions which may not pose a
threat to the integrity of the levee

6
ALTERNATIVE
“For economic efficiency, the amount of freeboard is
typically balanced against an acceptable amount of
overwash which does not pose a threat to the integrity
of the dam.”
Bruce Phillips et al. (2008)
Concerning the South Florida Water Management District
(SFWMD) Comprehensive Everglades Restoration Program
(CERP)
7
WAVE OVERWASH
• Periodic overwash of the levee crest by water from breaking
waves
 Still water level is below levee crest
 Intermittent flow
 Small volume of water
Wave Overwash
SWL
Levee
8
OVERWASH IS NOT OVERFLOW
• Overflow: Continuous flow over water over the levee crest
 Water level is above the levee crest
 Larger volume of water
 Steady flow
OVERFLOW
Water Level
Levee
9
OVERWASH IS NOT OVERFLOW
• Overflow: Continuous flow over water over the levee crest
 Water level is above the levee crest
 Larger volume of water
 Steady flow
OVERFLOW
Water Level
Levee
10
PURPOSE OF THE REVIEW
Answer the question:
What is an “acceptable amount” of overwash?
Specifically for
grass covered clay and sand levee
11
PROBLEM FORMULATION
Two ways to formulate the acceptable overwash:
• Specify threshold overwash rate
 Little to no damage expected for very long duration

Lower risk
• Specify a combination of overwash rate & duration



Allow acceptable level of damage
Overtopping stops before levee failure
Higher risk
12
PRESENT STUDY
Specify threshold overwash level
What is an acceptable threshold overwash rate?
13
THRESHOLD LEVEL
• Hughes (2007, USACE Coastal and Hydraulics
Laboratory)
• Summarized guidelines and tests to date
Source
Type/Condition
CEM Guidelines for
Irregular Average Wave
Grass Sea Dikes
Overtopping Damage
Criteria
Dutch Guidelines for
Sandy soil, poor turf
Average Wave Overtopping
for Grass-Covered Sea
Clayey soil with relatively good grass
Dikes
Goda (1985)
Back slope of embankments & seawalls
Overtopping Rate
(cfs/ft) at Start of
Damage
0.01 – 0.1
0.001
0.01
0.2 – 0.5
14
HUGHES (2007) CONCLUSIONS
• 0.1 cfs/ft quite conservative on grass covered
clay dikes
• Recent tests indicated 0.25 cfs/ft “might be okay
under ideal conditions”
15
HOW MUCH IS 0.1 cubic feet?
• 0.1 cubic feet just over 2 liters = 1 soda bottle ≈ 3 qts
≈ ¾ gal
• 0.01 cubic feet ≈ 10 oz. = small water bottle ≈ ½ pint
0.07 cubic feet
10 oz. ≈ ½ pint
≈ 0.01 cubic feet
2 liter ≈
½ gal.
16
THRESHOLD LEVEL VALUE
• How good is 0.1 cfs/ft?
• Review existing literature to determine level
17
Review of Testing
Literature
18
OVERWASH TESTS
• Data compiled and analyzed by various agencies



Academic
Government
U.S., Japan, and Europe
• Goal to determine maximum discharge that will not
cause damage to the given levee (threshold)


Interested in damage caused by overwash
Damage to the landward-side/”inner slope”/”back
slope”
19
LOCATION OF DAMAGE
seaward side
lake side
reservoir side
“outer slope”
Wave Overwash
landward side
“inner slope”
“back slope”
SWL
Levee
20
SMITH ET AL. (1994)
•
•
•
•
Smith, Seiffert, Van der Meer (Netherlands)
“Delta Flume” (wave flume, 7 m crest, depth ~5 m)
Primarily testing the sea-side of the dike (levee)
Grass and clay blocks on slopes
21
SMITH ET AL. (1994)
• Erosion Zone 3: crest and back slope
• Up to 0.27 cfs/ft, no erosion (0 mm) after 10 hours
Erosion rate
0 mm/hour
22
MÖLLER ET AL. (2002)
• Möller, Weissmann, Schüttrumpf, Grüne, Oumeraci,
Richwien, Kudella (Germany)
• Large scale tests to look at erosion from wave
overtopping for specific soil conditions (different clays)
23
MÖLLER ET AL. (2002)
• Determined the time to initiate erosion on the landward/inner
slope due to overwash (duration limit)
• Time to cause damage reduced as sand content increased
• 60% sand content lead to drastic reduction in resiliency
Clay
Silt
Sand
q (cfs/ft)
time
Clay 1
35%
53%
12%
0.01
2 hours
Clay 2
20%
45%
35%
0.01
1 hour
Clay 3
10%
30%
60%
0.005
10 min
24
TESTING SUMMARY
Source
Levee Type
Finding (erosion threshold
unless indicated)
Smith et al. (1994)
3:1 slope, grass & clay blocks
0.27 cfs/ft 10 hrs
3:1 slope, bare clay
0.01 cfs/ft 2hrs
3:1 slope, mostly sand
0.005 cfs/ft 10 min
Möller et al. (2002)
25
PULLEN ET AL. (2007)
EUROPEAN OVERTOPPING MANUAL
• Chapter 3 of the European Overtopping Manual
• Report of tests conducted in 2007 on a real dike (levee)
in the Netherlands
Levee Type
Overwash Rate
Landward slope of 3:1
“fairly good clay” (sand content < 30%)
grass covered
Little erosion up to 0.5 cfs/ft
Same dike
Grass removed  bare clay
Erosion at 0.001 cfs/ft
Near breach after 6 hours at 0.1 cfs/ft
26
TESTING SUMMARY
Source
Levee Type
Finding (erosion threshold
unless indicated)
Smith et al. (1994)
3:1 slope, grass & clay blocks
0.27 cfs/ft 10 hrs
3:1 slope, bare clay
0.1 cfs/ft erosion at 2 hrs
3:1 slope, mostly sand
0.005 cfs/ft erosion at 10 min
3:1 slope, grass & clay
0.5 cfs/ft no erosion
3:1 slope, bare clay
Erosion at 0.001 cfs/ft
Möller et al. (2002)
Pullen (2007)
27
PHILLIPS ET AL. (2007 AND 2008)
• Phillips, Hachenburg, Clark, Kivett (U.S.)
• Research for SFWMD Comprehensive
Everglades Restoration Program
• Tests on three levees with special
apparatus
C-43
C-44
EAA A-1
28
PHILLIPS ET AL. (2007 AND 2008)
C-43
Reservoir
Material
Finding
C-43
fine – silty sand, grass
significant erosion at
0.01 cfs/ft
C-44
fine sand, sod
(better sod than C-43)
minimal erosion up to
0.1 cfs/ft
EAA A-1
bare limestone + silty
carbonate sands
only surficial erosion up
to 0.23 cfs/ft
(self-armoring)
C-44
EAA A-1
29
TESTING SUMMARY
Source
Levee Type
Finding (erosion threshold
unless indicated)
Smith et al. (1994)
3:1 slope, grass & clay blocks
0.27 cfs/ft 10 hrs
3:1 slope, bare clay
0.1 cfs/ft erosion at 2 hrs
3:1 slope, mostly sand
0.005 cfs/ft erosion at 10 min
3:1 slope, grass & clay
0.5 cfs/ft
3:1 slope, bare clay
0.001 cfs/ft
Grass & clay
0.01 – 0.1 cfs/ft
Bare limestone & carbonate sand
0.23 cfs/ft
Möller et al. (2002)
Pullen (2007)
Phillips et al. (2008)
30
VAN DER MEER ET AL. (2009)
• Van der Meer, Schrijver, Hardeman, Hoven, Verheij,
Steendam (Netherlands)
• Wave overtopping simulator
31
VAN DER MEER ET AL. (2009)
• Wave overtopping simulator
• Grass on clay dike
• No failure up to 0.3 cfs/ft
32
TESTING SUMMARY
Source
Levee Type
Finding (erosion threshold
unless indicated
Smith et al. (1994)
3:1 slope, grass & clay blocks
0.27 cfs/ft 10 hrs
3:1 slope, bare clay
0.1 cfs/ft erosion at 2 hrs
3:1 slope, mostly sand
0.005 cfs/ft erosion at 10 min
3:1 slope, grass & clay
0.5 cfs/ft
3:1 slope, bare clay
0.001 cfs/ft
Grass & clay
0.01 – 0.1 cfs/ft
Bare limestone & carbonate sand
0.23 cfs/ft
Grass & clay
0.3 cfs/ft no failure
Möller et al. (2002)
Pullen (2007)
Phillips et al. (2008)
Van der Meer (2009)
33
THORNTON ET AL. (2012)
• Thornton, Scholl, Hughes, Abt (U.S.)
• Tests at Colorado State University (CSU) Wave
Overtopping Test Facility
34
THORNTON ET AL. (2012)
• Tests at CSU for New Orleans USACE
• Clay with various grasses
Total Time Max. Overtopping
End Result
(hours)
Rate (cfs/ ft)
Bare Clay
1.3
0.2
Severe Erosion
Bermuda Grass
24
4.0
No Damage
Bahia Grass
17
3.0
No Damage
Bermuda w/TRM
9
4.0
No Damage
Bermuda w/HPTRM
9
4.0
No Damage
Bermuda w/Wheel Ruts
9
4.0
Minor Erosion
Lime-Stabilized Clay
2
4.0
Severe Erosion
Articulated Concrete Block
3
4.0
Minor Erosion
Dormant Bermuda Grass
3
2.5
Significant Erosion
Levee Slope Surface
35
TESTING SUMMARY
Source
Levee Type
Finding (erosion threshold
unless indicated
Smith et al. (1994)
3:1 slope, grass & clay blocks
0.27 cfs/ft 10 hrs
3:1 slope, bare clay
0.1 cfs/ft erosion at 2 hrs
3:1 slope, mostly sand
0.005 cfs/ft erosion at 10 min
3:1 slope, grass & clay
0.5 cfs/ft
3:1 slope, bare clay
0.001 cfs/ft
Grass & clay
0.01 – 0.1 cfs/ft
Bare limestone & carbonate sand
0.23 cfs/ft
Grass & clay
0.3 cfs/ft no failure
Grass & clay
3 – 4 cfs/ft 17+ hrs
Bare clay
0.2 cfs/ft erosion < 2 hrs
Möller et al. (2002)
Pullen (2007)
Phillips et al. (2008)
Van der Meer (2009)
Thornton et al. (2012)
36
USACE (2013)
GREATER NEW ORLEANS HURRICANE AND STORM
DAMAGE RISK REDUCTION SYSTEM (HSDRRS)
• Reviewed CSU tests for HSDRRS
• Recommended



Rate related to calculation formula confidence
Mean rate: 0.01 cfs/ft
90% non-exceedance confidence rate: 0.1 cfs/ft
37
THORNTON ET AL. (2014)
• 12 full-scale wave overtopping tests of grass sod placed
atop sandy soils
• Grass resiliency was found to be a function of


cumulative wave overwash volume
grass root parameters
38
TESTING SUMMARY
Source
Threshold Overwash Rate
(cfs/ft)
USACE (2013) HSDRRS
0.01
Phillips et al. (2008)
0.01 – 0.1
Smith et al. (1994)
0.27
Van der Meer (2009)
0.3
Pullen (2007)
0.5
Thornton et al. (2012)
3 – 4 (17+ hrs)
Pullen (2007)
0.001
Möller et al. (2002)
0.1 (2 hrs)
Thornton et al. (2012)
0.2 (< 2 hrs)
sand
Möller et al. (2002)
0.005 (10 min)
Bare limestone & carbonate sand
Phillips et al. (2008)
0.23
Levee Type
Grass covered clay
Bare clay
39
GENERALIZED RESULTS FOR ALL TESTS
• Grassed clay slopes



Damage threshold ~ 0.01 – 0.1 cfs/ft
Known to resist erosion up to 0.3 – 0.5 cfs/ft
Clay (sand ‹30%) with grass  “highly erosion resistant”
• Grassed sand or bare clay slopes

Damage threshold ~ 0.001 cfs/ft
• Grass resiliency a function of


cumulative wave overwash volume
Extent & quality of grass root system
40
THANK YOU
Questions?
41
REFERENCES
Allsop, W.; T. Bruce; T. Pullen; J.W. Van der Meer. 2008. Direct Hazards From Wave Overtopping
– The Forgotten Aspect Of Coastal Flood Risk Assessment? Proceedings of 43rd Defra Flood and
Coastal Management Conference, 1-3 July 2008, Manchester University.
Dean, R.G.; J.D. Rosati; T.L. Walton; B.L. Edge. 2010. Erosional equivalences of levees: Steady
and intermittent wave overtopping. Journal of Ocean Engineering, No. 37, pp.104 – 113.
Hughes, S.A. 2007. Evaluation of Damage Thresholds for Levees. Presentation at Coastal and
Hydraulics Laboratory, U.S. Army Engineer Research and Development Center Technical Review
Workshop, 8 February 2007.
Hughes, S.A. 2008. Combined Wave and Surge Overtopping of Levees: Flow Hydrodynamics and
Articulated Concrete Mat Stability. U.S. Army Corps of Engineers, Engineering Research and
Development Center/Coastal Hydraulics Laboratory (ERDC/CHL) TR-08-10, August 2008.
Möller, J.; R. Weissmann; H. Schüttrumpf; J. Grüne; H. Oumeraci; W. Richwien; M. Kudella.
2002. Interaction of Wave Overtopping and Clay Properties for Seadikes. Proceedings of 28th
International Conference on Coastal Engineering, Cardiff, Wales, July 2002.
42
REFERENCES
Phillips, B.A.; B.J. Hachenburg; J.R. Kivett. 2008. Results from Overwash Testing on Earthfill
Embankments in South Florida. 28th Annual U.S. Society on Dams (USSD) Conference Portland,
Oregon, April 28 - May 2, 2008
Phillips, BA, B.J. Hachenburg; K.C. Clark; J.R. Kivett. 2007, Over the top – results from overwash
testing on embankment dams in south Florida, Proceedings from the U.S. Association of State
Dam Safety Officials Dam Safety Conference.
Pullen, T., Alsop, N.W.H., Bruce, T., Kortenhaus, A., Schuttrumpf, H., and van der Meer, J.W.,
2007. Wave Overtopping of Sea Defences and Related Structures: Assessment Manual. (EurOtp
Manual) .
Shewbridge, S. 2014. Personal communication with Stephen Whiteside, September 30, 2014.
Scott E. Shewbridge, Ph.D., P.E., G.E. U.S. Army Corps of Engineers, Institute for Water
Resources, Risk Management Center, Lakewood, Colorado.
[email protected].
43
REFERENCES
Smith, G.M.; J.W.W. Seijffert; J.W. Van der Meer. 1994. Erosion and Overtopping of a grass dike –
Large Scale Model Tests. Proceedings. 24th Int. Conf. On Coastal Engineering. pp. 2639-2652.
Steendam, G.J.; Y. Provoost; J.W. Van der Meer. 2012. Destructive Wave Overtopping And Wave
Run-Up Tests On Grass Covered Slopes Of Real Dikes. Proceedings of 33rd Conference on
Coastal Engineering, Santander, Spain, 2012.
Temple, D.M., and W. Irwin. 2006. Allowable Overtopping of Earthen Dams. Dam Safety 2006.
Proceedings of the Association of State Dam Safety Officials Annual Conference, Boston,
Massachusetts, September.
Thornton, C.I.; S.A. Hughes; J.S. Beasley. 2014. Full-Scale Wave Overtopping Resiliency Tests of
Grass Established on Sandy Soils. Proceedings of 3rd International Association for HydroEnvironment Engineering and Research (IAHR) Europe Congress, Porto, Portugal, April 14-16,
2014.
Thornton, C.; B. Scholl; S. Hughes; S. Abt. 2012. Full-Scale Testing of Levee Resiliency during
Wave Overtopping. Proceedings of 6th International Conference on Scour and Erosion, Paris,
France, August 27-31, 2012.
44
REFERENCES
Tucker, R,C.; M.J. Reynolds; E.K. Landowski. 2013. Dynamic Wave Overtopping Tests for Sandy
Reservoir Embankments Exposed to Tropical Cyclones. Proceedings of Tenth ICE Coasts, Marine
Structures and Breakwaters, Edinburgh, UK, 18-20 September 2013.
USACE, 2011. Coastal Engineering Manual. U.S. Army Corps of Engineers, Engineering Manual
1110-2-1100, Coastal Hydraulics Laboratory, Vicksburg, MS.
Van der Meer, J.W.; B. Hardeman; G.J. Steendam; H. Schüttrumpf; H. Verheij. 2010. Flow depths
and velocities at crest and inner slope of a dike, in theory and with the Wave Overtopping
Simulator, Proceedings International Conference on Coastal Engineering, Shanghai, ASCE.
China.
Van der Meer, J.W.; R. Schrijver; B. Hardeman; A. Van Hoven; H. Verheij; G.J. Steendam. 2009.
Guidance on erosion resistance of inner slopes of dikes from 3 years of testing with the Wave
Overtopping Simulator. Proceedings of ICE, Coasts, Marine Structures and Breakwaters 2009,
Edinburgh, UK.
USACE. 2013. Greater New Orleans Hurricane and Storm Damage Risk Reduction System.
HSDRRS Resiliency Presentation, U.S. Army Corps of Engineers, July 18, 2013.
45