Full document / COSOC-W-86-002 - the National Sea Grant Library

we entertain their suggestions for judicious use of the dredge
material.
Southwest Pass. We first started creating marsh with dredged material
along Southwest Pass of the Hisslsslppi Elver. There we discovered that
If we kept the initial height of the material below six feet, it would
generally compact and settle into the Intertldal zone and marsh grasses
would colonize it. Moving the dredge pipe more often would probably
create more marsh. However, with our limited maintenance budget, this
Is not possible. We have chosen an enclosed area on the South side of
the pass and applied for money under Section 150 of the Water Resources
and Development Act of 1976. We would use the money to keep the initial
height at five feet and monitor this to see if more marsh is created.
We are presently dealing with the leasors of the land to attempt to work
out Institutional problens.
Harsh Creation. Table 1 indicates the acres of marsh we have created
by
TABLE 1
ACRES OF MARSH CREATED
Location Land Ownership Harsh Hud Flats !/
KR-GO jetties State 30 140
MR-GO inland Private 20
Tiger Pass State 230
Avoca Lake Private 600
Sweet Lake State 90
Sabine NWR Federal refuge 200
Atachafalaya Delta State mgmt area 60 300
V These will probably become marsh once we place dredged material on
them again.
carefully choosing disposal sites and moving the dredge pipe as often as
practical. As can be seen, we have tried to build marsh on public lands
as often as possible and have built it in state water bottoms in other
cases. Occasionally ve have no choice but to place the material in 4to
6-foot deep open water. It takes more than one dredging cycle to
create marsh In such areas and much material Is lost. The Ideal area
for marsh creation consists of nearly totally enclosed ponds that are
1-3 feet deep. The utilization of sediment Is more efficient In such
areas. In order to estimate the Initial height of the dredged material,
it is necessary to take into account such variables aa consolidation,
subsidence, erosion, accretion, water depth, and sediment type. As we
become more experienced we became more accurate in our estimates. In
1981, we created 600 acres of marsh in Avoca Lake by diking the area and
limiting Initial height to 3.0 HLG feet. Now over half of this marsh is
gone. In our maintenance dredging this year, we will increase initial
height of the material.
737