Reusing Dredge Material on a Tidal Wetland
Alison Rogerson1, Andy Howard 1, Bart Wilson2
1 Delaware Department of Natural Resources and Environmental Control2 U.S. Fish and Wildlife Service
December 12, 2016
Project origin
• Delaware Wetland Conservation Strategy goal
• DNREC desire to find alternate uses
• Funded task under EPA wetland grant
• Goal:– Test the efficacy of restoring tidal wetland with dredge
material
– Investigate techniques, equipment, logistics, results
– Work towards developing a DNREC program
– Share as much information as possible
Project Site
Piney Point Tract of Assawoman Wildlife AreaDagsboro, DE
Background
- multi agency and partner project- tidal marsh restoration via thin layer application of dredge material-raise elevation to 1.05’ NAVD88- supply sediment and boost surface elevation-22 acres-10,000yd³
Upland Disposal
Aerial Application
Sediment sills: straw bales and waddles
Demonstration:February 25- March 25, 2013
Continuation:September 9-December 21, 2013
Southwest (SW)
Southeast (SE)
RTN Survey transects
elevation goal was 1.05 ft
Plant Regrowth
Biomass and Bearing Capacity
0
1
2
3
4
5
6
7
8
9
10
275
325
375
425
475
525
575
2012 2013 2014 2015B
ear
ing
Cap
acit
y
Bio
mas
s (g
)
Year
DemonstrationBiomass SW
ContinuationBiomass SE
DemostrationBearing SW
ContinuationBearing SE
2016
Feldspar marker horizons
Plot 1
Plot 4
Feldspar marker horizons
0
20
40
60
80
100
120
140
160
180
200
Mat
eri
al T
hic
kne
ss (
mm
)
Plot 1 Demonstration Plot 2 Demonstration Plot 3 Demonstration
Plot 4 Continuation Plot 5 Continuation
Lessons Learned:
• Site specific conditions will vary greatly!
• Aerially broadcasting material is possible
• Spray distance is limited by debris and wind
• Difficult to measure precisely how much is being applied
• Limit sediment to 10-15 cm
• Do not apply before heavy freeze
• Vegetation prevents major sediment runoff
• More feldspar plots
• Monitor mussels
Thanks for listening!
Alison Rogerson
Wetland Monitoring and Assessment Program
DNREC
302-739-9939
Cryogenic coring for feldspar horizon markers
measuring accretion thickness and surface movement
