Sediment Management Technologies W. H. McAnally PhD, PE, D.CE, D.NE, F.ASCE Research Professor of Civil & Environmental Engineering Mississippi State University, USA. R. Kirby BSc, PhD, C.Geol, Dist.D.NE, Director & Board Member Sediment Innovation Centre (SICEM) Emden, Germany.

Port & Channel Sedimentation Sediment accumulation reduces available depth Dredging & disposal are expensive Dredging & disposal are often environmentally disruptive Environmental windows limit dredging Placement sites are limited

Engineering Solutions Krone’s 3 ways to address sediment deposition: Keep sediment out Keep it moving Remove it Photos courtesy of Corps of Engineers

PIANC WG 102: Minimizing Harbor Siltation Six Methods Taxonomy METHODDESCRIPTION 1. Keep Sediment Moving (KSM) and mainly passive: Locate/relocate port to deeper water, locate berths alongside channels rather than on waterway margin, apply equilibrium regime theory concepts, dredge channels parallel to natural flow, etc. 2. KSM and passiveLongitudinal/perpendicular training walls/groins, dikes, or sills. 3. KSM and activeBed -mounted, automatic pumps fed by water injection, and applicable at impounded or semi-enclosed basins; early stage (i.e. before consolidation) water injection alone; bar/shoal removal, scour/propeller jets, etc. 4. Keep Sediment Out (KSO) and active For impounded docks, adopt low solids, surface water intakes, or resort to intermediate settlement basins, etc. 5. KSO Through Passive Structures: For impounded docks, adopt low solids, surface water intakes, or resort to intermediate settlement basins, etc. 6. Keep Sediment Navigable (KSN) and passive/active Adopt Passive or Active Nautical Depth and Conditioning

COPRI: Sed Solutions Taxonomy CATEGORYSTRATEGYEXAMPLES Prevention KSP – Keep Sediment in Place Erosion control on land and/or bed and banks KSO – Keep Sediment Out Sediment Traps, Gates and Dikes, Channel Separations KSM – Keep Sediment Moving Training Structures, Agitation, Flocculation Reduction, Flows Treatment KSN – Keep Sediment Navigable Nautical Depth Definition, Aerobic Agitation DRS – Dredge and Remove Sediment Placement in confined disposal facilities or offshore, Permanent beneficial uses DPS – Dredge and Place Sediment Bypass sediment (KSM), Temporary beneficial uses AccommodationAdapt (to Changing Sediment Regime) Flexible infrastructure, opportunistic agriculture, coastal setbacks

Fine, Cohesive Sediments Diameter < 20 – 40 μm Form flocs – low density, mostly water Form Fluid Mud in high concentrations False acoustic “bottom” fathometer signals Require dredging large volumes of muddy water Photos courtesy of Chris Zabawa, EPA

Nautical Depth Firm Bottom Fluid MudCOUNTRYPORT The Netherlands Rotterdam BelgiumZeebrugge ChinaYangtze China Liang yungang China Tianjing xingang UKAvonmouth FranceDunkirk FranceBordeaux France Nantes - Saint Nazaire GermanyEmden ThailandBangkok SurinamParamaribo French GuianaFrench GuianaCayenne

Fluid Mud in Sediment Profiles Sediment concentration or density Mixed layer mobile suspension Stratified mobile suspension Lutocline shear layer Fluid mud Deforming bed Stationary fluid mud Stationary bed Depth below water surface Primary lutocline Secondary lutocline Zero velocity plane Sediment transport depth Suspension (zero effective stress) Bed (measurable effective stress) X X X Sediment concentration or density Depth below water surface Fluid Mud

Passive Nautical Depth Map Fluid Mud Density Dredge to keep 1.2 kg/cu m below channel prism Zeebrugge Harbor entrance density contours at project depth

Active Nautical Depth Create and maintain fluid mud in channel/port by oxygenation & stirring Presence of fluid mud prevents entry of new sediment Vessels sail through muddy water Example: Emden Port

Emden: Self-propelled hopper with low power underwater pump for infrequently fluidising, raising, oxidising and redepositing fluid mud. (Wurpts, 2005).

Maintenance dredging reduced from 4X10 6 cu m/yr to 0 Costs reduced from €12.5M to €2M/yr Chemolithotrophic bacteria break down the Tri-butyl Tin Formerly intractable problem has disappeared Emden Active Nautical Depth

Gulf Ports Project PURPOSE: –Find feasible, affordable engineering solutions to reduce or eliminate port maintenance dredging requirements. APPROACH: –Identify sedimentation problems and causes –Devise approaches to decrease dredging costs.

Pascagoula Two harbors Deep draft port ~ 40+ ft Both local and federal channels Top 20 largest U.S. ports Fluid mud Dredged every 18 months About $450,000 per cycle Limited disposal space Nautical depth would work

Conclusions Sediment Management: – Can reduce dredging costs – Is sustainable – Comes in many different forms Nautical Depth is a proven solution –Used ~40 years in Rotterdam & worldwide –Should be used in U.S.