Student number: 5821797 Effects of dredging and dumping in laboratory scale experiments of estuaries Cox, J.R. (Jana) Student number: 5821797 Utrecht University, Department of Physical Geography Faculty of Geosciences March 2018 – final version Master: Earth Surface and Water Track: Coastal and fluvial morphodynamics Supervisors: J.R.F.W Leuven & Prof. 0 M.G. Kleinhans Contents Table of figures ............................................................................................................................................. 3 Abstract ........................................................................................................................................................ 8 1. Introduction ......................................................................................................................................... 9 1.1 Review of the effects of dredging and dumping on estuaries & suggested mechanisms ................... 9 1.2 Description of the Western Scheldt estuary ..................................................................................... 11 1.2.1 Geological history of the estuary ............................................................................................... 11 1.2.2 Morphological development of the Western Scheldt estuary ................................................... 12 1.3 Current morphology of the Western Scheldt ................................................................................... 13 1.4 Sediment balance of the Western Scheldt estuary........................................................................... 14 1.5 History of dredging in the Western Scheldt ................................................................................ 14 1.5.1 Introduction to dredging in the Western Scheldt ...................................................................... 14 1.5.2 History of dredging in the Western Scheldt ............................................................................... 15 1.5.3 Volumes of dredged sediment .................................................................................................. 16 1.6 Effects of dredging on morphology evident in DEMs of the Western Scheldt ............................ 19 1.7 History of dumping in the Western Scheldt ................................................................................ 23 1.7.1 Introduction to dumping in the Western Scheldt ...................................................................... 23 1.7.2 Dumping locations: how to choose?.......................................................................................... 24 1.7.3 1990s: The East-West strategy .................................................................................................. 24 1.7.4 The 2010 Strategy: flexible dumping ......................................................................................... 24 1.7.5 Sediment exchange between cells in the Western Scheldt ....................................................... 28 1.7.6 Sandbar (shoal) dumping ........................................................................................................... 28 1.7.7 Secondary (side) Channels ......................................................................................................... 28 1.7.8 Deep parts of the fairway – scours ............................................................................................ 29 1.8 Effects of dumping on morphology evident in the DEMs of the Western Scheldt ........................... 29 1.9 Future plans for the Western Scheldt............................................................................................... 32 1.9.1 The Long-Term Vision ................................................................................................................ 32 1.9.2 Building with Nature .................................................................................................................. 32 1.9.3 Future plans for sediment management ................................................................................... 33 1.10 Summary of different dredging and dumping techniques: how do they dredge and dump? ......... 33 1.11 Hypotheses of the effects of dredging and dumping ...................................................................... 33 2. Methods and materials .......................................................................................................................... 35 1 2.1 Western Scheldt data collection & analysis ...................................................................................... 35 2.2 Designing experiments for the Metronome ..................................................................................... 35 2.2.1 What is the Metronome? .......................................................................................................... 35 2.2.2 Experimental setup and settings – creating the shipping fairway ............................................. 24 2.2.3 Dredging the shipping fairway ................................................................................................... 25 2.2.4 Dumping locations ..................................................................................................................... 26 2.3 Data collection.................................................................................................................................. 26 2.3.1 DEMs & orthophotos ................................................................................................................. 26 2.3.2 Time lapse imagery & blue colour photos ................................................................................. 29 2.3.3 Water levels & Particle Image Velocimetry (PIV) measurements .............................................. 29 2. 3.4 Intertidal area calculation methods .......................................................................................... 29 2.3.5 Control experiment ................................................................................................................... 29 3. Results .................................................................................................................................................... 31 3.1 Large scale effects of dredging and dumping ................................................................................... 31 3.1.1 Estuary width and morphological composition ......................................................................... 33 3.1.2 Estuary stability ......................................................................................................................... 36 3.1.3 Intertidal area, subtidal area and supratidal area ..................................................................... 38 3.2 Medium scale effects of dredging and dumping .............................................................................. 39 3.2.1 Main channel dimensions .......................................................................................................... 39 3.3.1 Water levels ............................................................................................................................... 42 3.3.2 High water, low water and tidal range ...................................................................................... 43 3.5 Small (feature) scale effects of dredging and dumping .................................................................... 46 3.5.1 Response of the shoals .............................................................................................................. 46 3.5.2 Average heights of the shoals .................................................................................................... 46 3.5.3 Cross sections of shoals ............................................................................................................. 46 3.5.4 Summary of the morphological response of the shoals & effect of sedimentation................... 48 3.5.5 Reaction of the side channels .................................................................................................... 53 3.5.6. Scours and rate of infilling ........................................................................................................ 56 3.6 A note on experimental issues and drawbacks................................................................................. 59 4. Discussion & implications ................................................................................................................... 61 4.1 Typical dredging and dumping volumes and location ...................................................................... 61 4.2 Dredging the crosses ........................................................................................................................ 62 2 4.3 Estuary shape and stability ............................................................................................................... 64 4.4 Response of main channel to dredging and dumping ...................................................................... 66 4.5 Velocity and tidal propagation ......................................................................................................... 67 4.6 Changing water levels....................................................................................................................... 68 4.6.1 High water and low water ........................................................................................................