Loxahatchee River Management Coordination Council Meeting, January 30, 2012
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Transcript of Loxahatchee River Management Coordination Council Meeting, January 30, 2012
Saltwater Barrier: Is it a Restoration Alternative for the Northwest Fork of
the Loxahatchee River?
Loxahatchee River Management Coordination Council Meeting, January 30, 2012
Patricia Walker
Loxahatchee River
Watershed
Northwest Fork of the Loxahatchee River
THE 1975 PROPOSAL
Jupiter Inlet District (JID) and Florida Department of Natural Resources (FDNR) applied to the U.S. Army Corps of Engineers for a permit to construct a saltwater barrier weir in the Northwest Fork near River Mile 6.0.
Construction of a weir at an elevation 4 feet below mean sea level within the south boundary of Jonathan Dickson State Park (JDSP) and near an existing power line crossing.
THE 1975 PROPOSAL
The U.S. Fish and Wildlife Service (FWS) expressed concern that there was no hydrologic study that could confirm the effectiveness of such a weir structure in preventing saltwater intrusion.
FWS Recommendations -Deny the permitStudies to show other salinity management
alternatives
THE 1986 FEASIBILITY STUDY
Jupiter Inlet District (JID) initiated the study
Feasibility of placing one or more submerged weir(s) to limit the salinity intrusion
THE 1986 FEASIBILITY STUDY
The literature search found that “little published information exists on the use or performance of submerged weirs for salinity control.”
The feasibility report concluded that design of a submerged structure on the Loxahatchee River would require comprehensive study to verify its performance.
2005 SFWMD MODELING EVALUATION
Chapter 9 of the Restoration Plan
Using a calibrated 3-D hydrodynamic model (CH3D)
2005 SFWMD MODELING EVALUATION
Barrier Location
2005 SFWMD MODELING EVALUATION
2 Barrier Types
Crest elevation = 1.0 ft NGVD29Crest elevation = +0.1 ft NGVD29Crest elevation = 1.0 ft NGVD29
0 10 20 30Ju lia n da y
-0.4
0
0.4
0.8
Tida
l ele
vatio
n (m
, NGV
D29)
Tide elevation at the Inlet
Elevation Change with a Barrier
8 8.4 8.8 9.2 9.6 10
-1
0
1
2
Sur
face
Ele
vatio
n (ft
NG
VD
29)
WATER QUALITY CONCERNS
Nutrient concentrations and possible algal problems occurring behind the structure.
A saltwater barrier can cause both a temperature and dissolved oxygen imbalance in and around its vicinity.
Adding a dam structure to the river may increase the levels of fecal coliform bacteria as a result of reduced tidal flushing.
ECOLOGICAL CONCERNS
The barrier will have a negative impact on the spawning and nursery areas for fish.
Can lose the
entire floodplain due to inundation.
2005 SFWMD MODELING EVALUATION Conclusions
Type 1 barrier is unlikely to achieve the target of salinity reduction at River Mile 6.2 (2 ppt) without violating minimum channel width guidelines for small craft navigation
Type 2 barrier is more effective in reducing/preventing salt intrusion. Given sufficient crest height, Type 2 barrier can achieve the salinity target at River Mile 6.2.
Due to concerns about disruption of navigation and ecological impacts, saltwater barrier was not chosen as a viable option by the Restoration Plan
Saltwater Barrier – Not a Restoration Alternative for the Northwest Fork of the Loxahatchee River
Thank you for your interest in the Northwest Fork of the Loxahatchee River!