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2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas 6 October, 2005 Minimization Of Sedimentation In Harbors.

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Presentation on theme: "2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas 6 October, 2005 Minimization Of Sedimentation In Harbors."— Presentation transcript:

1 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas 6 October, 2005 Minimization Of Sedimentation In Harbors And Marinas 2 nd Annual Dredged Material Management Summit Eric Smith and John Headland, Moffatt & Nichol

2 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas PRESENTATION TOPICS Why do We Dredge? Why Does Sedimentation Happen? How Can We Minimize Sedimentation? Examples Conclusions

3 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas To Deepen Waters For Vessel Access (New Work Dredging To Maintain Depths Subject To Sedimentation (Maintenance Dredging) Dredged Material Can Be Managed By Managing Sedimentation Reducing Sedimentation Keeps Sediment In The Natural System WHY DO WE DREDGE?

4 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas Sediment Movement and Tidal/Wave Conditions Are Balanced in Most Natural Systems Many Natural Systems Are Equilibrated And Free of Sedimentation or Scour Sedimentation Occurs When: There Is Sediment (Mud, Silt or Sand) In The Water Column Flow Velocities Are Not Strong Enough To Keep Sediment Moving (Usually a result of deepening for navigation/harbor development) WHY DOES SEDIMENTATION HAPPEN?

5 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas Build Marine Facilities In Naturally Deep Water (i.e. Dont Deepen) Otherwise, Simply: Keep Sediment Moving (KSM) Through The Harbor Keep Sediment Out (KSO) of the Harbor Both Strategies Involve Controlling Flow Conditions HOW CAN WE MINIMIZE SEDIMENTATION?

6 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas FLOW-THROUGH HARBORS/MARINAS Berths Parallel To Flow Newark Bay, NJ Wilmington, DE

7 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas SEDIMENTATION IN DEEPENED CHANNELS Q s in = u in c in h in Q s out = u out c out h out h in h out Because Q s out < Q s in Sedimentation Q s in, u in Sediment Transport InSediment Transport Out Q s out, u out Dredged Area Un-Dredged Area

8 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas Sedimentation = Sediment In – Sediment Out ΔQs = Q s in – Q s out ΔQs = c in U in d in – c out U out d out Where: ΔQs = Sedimentation Rate, c = sediment concentration No Sedimentation When U,d are constant Sedimentation When U out d in ) SIMPLIFIED PHYSICS OF SEDIMENTATION FOR FLOW THRU HARBORS & CHANNELS

9 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas Strategy is to: Place harbor & channels within naturally deep water Increase velocity in deepened area by engineering works Flow Training Structures That Maintain Velocities By flow augmentation with jets or injection dredging KSM IN FLOW-THRU HARBORS & CHANNELS

10 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas KSM- FLOW TRAINING STRUCTURES MAINTAIN VELOCITY IN A DEEPENED AREA Yangtze River, China Shooters Island, NY

11 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas KSM- FLOW TRAINING STRUCTURES Delaware Bay Mississippi River

12 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas KSM- FLOW AUGMENTATION WITH SCOUR JETS

13 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas KSM- FLOW AUGMENTATION WITH PROPELLOR JETS Propeller Jet System, Scour Systems

14 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas Systems Have Been Installed: Kings Bay, GA Savannah, NC Linden, NJ Grays Harbor Each Installation Has Eliminated Dredging Best-Suited For Berthing Areas System Keeps Sediment In The Natural System KSM- PROPELLOR/SCOUR JETS

15 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas HARBOR/MARINA BASINS Port Elizabeth Channel, NJ Manten, Holland Quiescent Basins

16 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas SIMPLIFIED PHYSICS OF SEDIMENTATION IN IN BASIN HARBORS

17 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas ΔQs = c p x Q e Where: c = sediment concentration outside of harbor p = basin trapping efficiency Q e = exchange rate through entrance of harbor Best Way To Reduce Sedimentation is To Reduce Q e SIMPLIFIED PHYSICS OF SEDIMENTATION IN IN BASIN HARBORS

18 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas FLOW PHENOMENA IN HARBOR BASINS Q e Depends on 3 Mechanisms: Horizontal Eddy Exchange (Can Be Reduced) Tidal Filling (Cannot Be Changed) Density Currents (Can Be Reduced)

19 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas HORIZONTAL EDDY EXCHANGE- HARBOR BASINS

20 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas SALT/FRESH WATER DENSITY CURRENTS- HARBOR BASINS Saltier Water Fresher Water Harbor Basin Channel Fresher Water Saltier Water Harbor Basin Channel Incoming Tide: Brings Saltier/Heavier Water To Basin Outgoing Tide: Brings Fresher/Lighter Water To Basin Even A Small Change In Salinity (i.e., 1-2 ppt) Can Exchange A Tremendous Volume Of Water, More Than Tide Or Eddy Exchange!!

21 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas METHODS TO REDUCE FLOW VOLUME EXCHANGE- IN HARBOR BASINS Narrow Entrance Use Only 1 Entrance Change Entrance Orientation Use Structures to Reduce f h Pile Groin Current Deflecting Wall (CDW) Modified CDW For Density Currents

22 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CLOSE SECOND ENTRANCE PORT OF BREMEN, GERMANY SECOND ENTRANCE

23 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas IN-SITU TREATMENT- PORT OF EMDEN, GERMANY SEDIMENTATION REDUCTION 67%

24 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas GROIN PILE FIELD- REDUCES f h By 30% CAN INTERFERE WITH NAVIGATION!

25 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CURRENT DEFLECTING WALL- REDUCES f h By 30% Kohlfleet Harbor Basin Hamburg, Germany

26 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CURRENT DEFLECTING WALL- KOHLFLEET BASIN

27 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CURRENT DEFLECTING WALL- PRINCIPLES Without CDW With CDW CDW

28 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CURRENT DEFLECTING WALL- FLOW PATTERNS

29 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas KOHLFLEET BASIN CDW REDUCES f h By ~35%

30 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CURRENT DEFLECTING WALL FOR DENSITY CURRENTS

31 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CURRENT DEFLECTING WALL FOR DENSITY CURRENTS Creates A Vortex Over The Width of The Basin Entrance CDW Decreases Water Exchange In Lower Layers By 40% During Flood Tide CDW & Sill Reduce Same to 70% Directs More Flow Into The Basin In Top Layers Not Yet Tested in Field Conditions

32 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CURRENT DEFLECTING WALL FOR DENSITY CURRENTS- PHYSICAL MODEL TESTS TIME (Sec) Dye Mass In Basin (g) Without CDW With CDW & Sill

33 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas Mobilize Sediments Near the Bottom Under Low Pressure Used Extensively In Europe To Move Sediments From Quiescent Areas To Areas of High Velocities Sediment Is Lifted Only A Few Feet Off Bottom Creating Little Turbidity Can Be Used To Move Sediments Up to 1000m 2 M m 3 Are Managed This Way in Port of Hamburg KSM- WATER INJECTION DREDGING

34 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas KSM- FLOW AUGMENTATION WITH WATER INJECTION DREDGING (WID) European Water Injection Dredger

35 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas KSM- FLOW AUGMENTATION WITH WATER INJECTION DREDGING (WID) BREMERHAVEN, GERMANY FAST-MOVING RIVER QUIESCENT BASIN

36 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas Historical Sedimentation 350,000 m 3 per year WID Used For 11 Years WID Reduced Sedimentation Rate To Zero Eliminated Need For Upland Placement Keeps Sediment In The System KSM- WID, PORT OF BREMERHAVEN, GERMANY

37 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas IN-SITU TREATMENT- PORT OF EMDEN, GERMANY FAST-MOVING RIVER QUIESCENT BASIN

38 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas In-Situ Treatment, PORT OF EMDEN, GERMANY Harbor Area Fronting Lock Subject To 2.5 cubic meters Per Year (deposited upland and/or offshore) The Deposit Starts As Fluid Mud & Eventually Consolidates Into Mud IST Consists of Removing Sediment From the Bottom into a Dredge Hopper, Exposing it to Oxygen (Oxygenating it), and Then Depositing it Back on the Bottom Sediment Is Not Removed Or Suspended Above Bottom Ships Sail Right Thru The Fluid Mud! IST, Performed Every 3 Months, Eliminated the Need For Dredging

39 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas IST, PORT OF EMDEN, GERMANY Suspend Sediment: While Alive, Organisms Act as Parachutes to Keep Sediment Suspended Fluid Mud: Organisms Form a Slime That Binds Particles To Form A Dense, Stable Suspension Mud: Results From Consolidation In Absence of In-Situ Treatment, Organisms Die Owing To Lack Of Oxygen IST Oxygenates Organisms In Order To Maintain Fluid Mud In Suspension

40 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas FLUID MUD THICKNESS- PORT OF EMDEN, GERMANY 3.3 m thick

41 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas FLUID MUD THICKNESS PORT OF EMDEN, GERMANY 210 kHz 15 kHz 210 kHz 15 kHz m Thick 3.5 m Thick April July FLUID MUD IS IN EQUILIBRIUM WITH RIVER/SEDIMENT CONDITIONS THICKNESS REMAINS CONSTANT OVER TIME!

42 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas IN-SITU TREATMENT- PORT OF EMDEN, GERMANY DEPTHS FLUID MUD THICKNESS

43 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas IN-SITU TREATMENT (IST)- PORT OF EMDEN, GERMANY

44 2 nd Annual Dredged Material Management Summit Minimizing Sedimentation In Harbors and Marinas CONCLUSIONS Dredged Material Can Be Managed Thru Sedimentation Management There Are A Number of Strategies For Reducing Sedimentation Including New Developments Proven in Europe These Strategies Keep Sediment In The System These Systems Can Be Very Cost-Effective and Are Equally Applicable To Large and Small Harbors


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