DREDGING THE PASS. 1999 Ten-Year Permit vs New Proposed Permit 1999 10-Yr Permit, Clam Bay...
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Transcript of DREDGING THE PASS. 1999 Ten-Year Permit vs New Proposed Permit 1999 10-Yr Permit, Clam Bay...
DREDGING THE PASS
1999 Ten-Year Permit vs New Proposed Permit
1999 10-Yr Permit, Clam Bay Restoration and Management Plan
The primary objective was environmental restoration of the ecosystem in particular the restoration of approximately 20 hectares of mangroves that died off in the northern end of the system along the strand road and upper clam bay
Today’s Proposed Permit, Clam Pass Maintenance Dredging
The primary objective is inlet maintenance to aid in flushing and improve environmental resources.
1996
Upper Clam Bay
Reminder of where we used to be…
Development Adjacent to Mangroves
Alteration of Natural
Hydrology
Change in Tidal Flow
Increased Freshwater
Runoff
Altered Hydroperiod Reduced Sheetflow
- Extended Surface Water Retention
- Surface Water Levels Increase
- Tidal Circulation in the Mangroves becomes stagnant
Prolonged Stress of
submerged aerial roots
Black Mangrove
Die-off
Below Ground Decay
Subsidence
Change in Avian Species UseDecline in Avian Populations
Decline in Benthic Invertebrate Community
Decline in Fisheries
Conceptual Model of a Black Mangrove Die-off
REMEMBER THIS
01-Aug-2002
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29-Aug-2002
30-Aug-2002
Rain
Rain
Full Moon
Rain
2"
6"
8"
(Reference) Surface Water Fluctuations During the Wet Season: Tidal Influence at a Station Situated Near the Gulf
01-Aug-2002
02-Aug-2002
04-Aug-2002
06-Aug-2002
08-Aug-2002
10-Aug-2002
12-Aug-2002
14-Aug-2002
16-Aug-2002
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20-Aug-2002
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24-Aug-2002
25-Aug-2002
27-Aug-2002
29-Aug-2002
31-Aug-2002
Full Moon
Rain Rain
1"
4"
7"
(Die-off) Surface Water Fluctuations During the Wet Season: Muted Tidal Signatures and Predominant Influence of Rain and Runoff
inch
esin
ches
Clam Bay 2002
NEED A COMPREHENSIVE PLAN TO PROTECT THE ESTUARY WHICH CONSISTS OF ENVIRONMENTAL RESOURCES THAT ARE FOUND IN THE PASS, BAYS AND TRIBUTARIES AND THE LANDWARD HABITATS INCLUDING THE MANGROVE FORESTS , SCRUB AND DUNES
Dredging Clam Pass Inlet ALONE is not answer to maintaining the health of the estuarine waterways and mangrove forest
When to Dredge?
Dredging should occur only when the hydrologic exchange between the Gulf and the Clam Bay estuary has been reduced to the point where the biological integrity of the entire system (water and forest resources) are at risk.
Clam Pass
1953
Clam Pass 1962
Cla
m P
ass
1995
Cla
m P
ass
2003
Inlet Dynamics are influenced by a variety of factors such as:
Inlet Current patterns driven by tides, waves, wind, severe weather, etc.
Constantly variable inlet hydrodynamics are influenced by tidal prism, channel and estuary morphology, slope, elevation, sediment type(s) and geological features, fresh water inflow, gross geometric variation, flow velocity, tidal phase and amplitude and phase, shoaling and scouring, etc…..
Clam Pass 2009
Clam Pass 2008
Circumstances that could necessitate dredging:
1)Pass completely closes due to a storm or other natural event
2)Inlet has lost hydraulic efficiency that is not recoverable through natural processes
Tide Gauges, Mangrove, Seagrass and other
Ecological IndicatorsMonitoring Plan
Purpose: To evaluate inlet characteristics and tidal dynamics within the entire Clam Bay system on a comprehensive long-term basis.
CLAM PASS
Proposed Dredging Template
HYDROLOGIC EFFICIENCY OF THE ENTIRE CLAM BAY
SYSTEM
ECOLOGICAL CONDITIONS OF
THE ENTIRE CLAM BAY SYSTEM
THERE IS NO CUT AND DRIED DECISION OF WHEN TO DREDGE
THE DECIESION SHOULD BE BASED UPON THE BEST SCIENTIFIC HYDROLOGIC AND ECOLOGIC DATA AVAILABLE AND BY WEIGHING THE BENEFITS OF DREDGING VS THE DETRIMENTS OF DREDGING IN
RELATION TO THE ENVIRONMENT