U.S. Army Corps of Engineers Investigation on the Implementation of Nautical Depth Tim Welp, Steve Reid, and Dennis Webb Tim Welp Research Hydraulic Engineer ERDC Coastal and Hydraulics Laboratory 25 October 2012
Definition of Fluid Mud Fluid mud is a high concentration aqueous suspension of fine-grained sediment in which settling is substantially hindered by the proximity of sediment grains and flocs, but which has not formed an inter-connected matrix of bonds strong enough to eliminate the potential for mobility, leading to a persistent suspension. McAnally et al. 2007
What is Fluid Mud?
Problem Statement Why Is It A Problem? Sounding pole, lead line, and acoustic echo sounding will generally not correlate with one another, or give consistent readings from one time to the next when the same type of instrument is used in fluid mud (Hydro EM). Measurement ambiguity has hindered optimization of Corps management of Gulfport Ship Channel.
Source: Kirby and Parker 1978
$1,000,000 $181,455
Nautical Bottom Definiton PIANC-IAPH 1997: the level where physical characteristics of the bottom reach a critical limit beyond which contact with a ship s keel causes either damage or unacceptable effects on controllability and manoeuvrability Nautical Bottom Approach Requires: practical fluid mud criterion & critical value practical, continuous survey method minimum underkeel clearance value knowledge about ship behaviour
Fluid Mud Field Drop 10 0 2 4 6 8 10 12 14 Admodus 10A Admodus 10B Admodus 10C BV Rheotune 10 (9/19) Rheotune 10 comp (9/21) SILAS Water/Silt interface SILAS 1.150 g/ml boundary SILAS 1.195 g/ml boundary SILAS seafloor CTD 1 (9/19) Depth (ft) 16 18 20 22 24 26 Water / Silt Interface 28 30 32 34 24 khz Depth 36 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 Density (g/ml)
Practical Continuous Survey Method Rheotune Density Probe SILAS
Practical Continuous Survey Method SILAS DIGITAL RECORDING LINE 17 LEGEND TOP SILT LAYER 1.200kg\liter DENSITY LEVEL TOP CONSOLIDATED MATERIAL SILAS SURVEY GULF PORT DIGITAL RECORDING OF ODOM ECHOTRACK MK III 24 khz FEQUENCY
World Wide Nauical Depth Criterion Critical Limits Density (g/cm 3 )
Economic Impact Study Results - 800,000 yd 3 /9 months, $2.1M -$5.6M - Estimate that if fluid mud layer excluded could reduce dredging in excess of 250,000 yd 3 - annual savings $550,000 to $1.4M - 50 year project life potential savings $28 to $70M - build 200 300 acre new CDF $28 -$49M - extend CDF life 10 years
SAM Hydro Survey Using SILAS & Rheotune
Nautical Bottom Definiton PIANC-IAPH 1997: the level where physical characteristics of the bottom reach a critical limit beyond which contact with a ship s keel causes either damage or unacceptable effects on controllability and manoeuvrability Nautical Bottom Approach Requires: practical fluid mud criterion & critical value practical, continuous survey method minimum underkeel clearance value knowledge about ship behaviour
Implementation Plan Upgrade SAM with state-of-practice fluid mud surveying equipment and train personnel on its use to determine where nautical bottom is (1.2 gm/cm 3 horizon). Develop hydrodynamic model for ERDC ship simulator to calculate ship response to the variety of forces (Gulfport-specific environmental and mariner controlled) being exerted upon the vessel w/o fluid mud. Modify ship simulator with Ghent University/Flemish Hydraulics Institute fluid mud/ship maneuverability hydraulic coefficients. Have Gulfport Pilots drive simulator with fluid mud, then with different fluid mud densities and underkeel clearances to accept nautical depth criteria. Monitor dredging to optimize maintenance dredging contract management.
Dr. Marc Vantorre EXPERIMENTAL PROGRAM Source: Dr. Marc Vantorre 2005 Towing tank for maneuvers in shallow water co-operation Flanders Hydraulics Laboratory & Belgium Ghent University, Belgium
ERDC Ship Simulator Collection & Rendering of Visuals
Implementation Plan Upgrade SAM with state-of-practice fluid mud surveying equipment and train personnel on its use to determine where nautical bottom is (1.2 gm/cm 3 horizon). Develop hydrodynamic model for CHL ship simulator to calculate ship response to the variety of forces (Gulfport-specific environmental and mariner controlled) being exerted upon the vessel w/o fluid mud. Modify ship simulator with Ghent University/Flemish Hydraulics Institute fluid mud/ship maneuverability hydraulic coefficients. Have Gulfport Pilots drive simulator with fluid mud, then with different fluid mud densities and underkeel clearances to accept nautical depth criteria. Monitor dredging to optimize maintenance dredging contract management.
Atchafalaya Bar Channel
Atchafalaya Bar Channel
High Resolution Density Profiler