The impact of dredge spoil dumping on coastal morphodynamics monitored by high resolution acoustic measuring instruments (outer Weser Estuary, German Bight) [Elektronische Ressource] / vorgelegt von Claudia Wienberg

Cwberg

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2003
• Nombre de lectures: 27
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

The impact of dredge spoil dumping
on coastal morphodynamics monitored by
high-resolution acoustic measuring instruments
(outer Weser Estuary, German Bight)





Dissertation
zur Erlangung des
Doktorgrades der Naturwissenschaften

im Fachbereich Geowissenschaften
der Universität Bremen





vorgelegt von
Claudia Wienberg
Bremen, August 2003





Tag des Kolloquiums:
02. Oktober 2003



Gutachter:
1. Priv. Doz. Dr. Dierk Hebbeln
2. Prof. Dr. Burghard Flemming



Prüfer:
1. Prof. Dr. Rüdiger Stein
2. Prof. Dr. Katrin Huhn Table of contents
Table of contents
Abstract ................................................................................................................................................... 1
Zusammenfassung ................................................................................................................................. 3

1 General Introduction ........................................................................................................................ 5
1.1 Motivation and main objectives.............................................................................................. 5
1.2 Estuaries: a general overview .................................................................................................. 6
1.2.1 Geology and sedimentology of coastal plain estuaries.............................................. 7
1.2.2 Hydrodynamics of tide-dominated estuaries.............................................................. 8
1.2.3 Morphology of tide-dominated estuaries.................................................................... 9
1.3 A regional case: the Weser Estuary ...................................................................................... 11
1.3.1 The Weser River... 11
1.3.2 Geomorphology of the Weser Estuary ..................................................................... 12
1.3.3 Hydrodynamics of the Weser Estuary....................................................................... 13
1.3.4 Sediment transport in the inner German Bight ....................................................... 14
1.4 Human impact on the Weser Estuary.................................................................................. 17
1.4.1 Historical review of anthropogenic interferences.................................................... 17
1.4.2 Consequences of the human impact.......................................................................... 19
1.4.3 Dredging and dumping................................................................................................ 20
1.5 Acoustic measuring instruments........................................................................................... 21
1.5.1 Multibeam echosounder systems ............................................................................... 21
1.5.2 Seabed classification systems ...................................................................................... 24
1.6 Overview of own research..................................................................................................... 28

2 Manuscript I ..................................................................................................................................... 29

‘The fate of dumped sediments monitored by a high-resolution
multibeam echosounder system, outer Weser Estuary, German Bight’

2.1 Introduction............................................................................................................................. 30
2.2 Regional setting ....................................................................................................................... 31
2.2.1 Study site.......... 33
2.3 Methods.................................................................................................................................... 34
2.3.1 Data acquisition ............................................................................................................ 34
2.3.2 Data processing ............................................................................................................ 35
2.3.3 Difference grids.... 36
2.4 Results and Discussion............................................................................................................ 36
2.3.4 Bathymetric maps. 36
2.4.1 Scour holes .................................................................................................................... 39
2.4.2 Accumulation-erosion balance ................................................................................... 40
2.4.3 Net sediment transport................................................................................................ 42
2.5 Conclusions.............................................................................................................................. 43 Table of contents
3 Manuscript II................................................................................................................................... 45

‘Subaqueous dunes in the outer Weser Estuary (German Bight)
and the impact of dumped sediments’

3.1 Introduction ............................................................................................................................ 46
3.2 Study area................................................................................................................................. 47
3.2.1 Geomorphology and sedimentology......................................................................... 47
3.2.2 Hydrography................................................................................................................. 49
3.3 Methods ................................................................................................................................... 49
3.3.1 Multibeam echosounder surveys ............................................................................... 49
3.3.2 Cross-sections............................................................................................................... 50
3.4 Results and Discussion.......................................................................................................... 52
3.4.1 Morphological dune characteristics........................................................................... 52
3.4.2 Impact of dumping...................................................................................................... 56
3.4.2.1 Shallowing of the seabed .............................................................................. 56
3.4.2.2 Change of dune morphology ....................................................................... 57
3.4.3 Migrational trend.......................................................................................................... 63
3.5 Conclusions............................................................................................................................. 67
3.6 Appendix ................................................................................................................................. 68

4 Manuscript III ................................................................................................................................. 69

‘Acoustic seabed classification in a dynamic environment
(outer Weser Estuary, German Bight) – quality control of human impact

4.1 Introduction.............. 70
4.2 Study area................................................................................................................................. 70
4.3 Methods ................................................................................................................................... 72
4.3.1 Acoustic seabed classification .................................................................................... 72
4.3.2 Sidescan sonar .............................................................................................................. 74
4.3.3 Sediment samples......................................................................................................... 74
4.4 Results and discussion ........................................................................................................... 74
4.4.1 Acoustic classes and sediment types......................................................................... 74
TM4.4.2 Comparison of sidescan sonar and QTC View ................................................... 77
TM4.4.3 Time series of successive QTC View surveys...................................................... 79
4.8 Conclusions............................................................................................................................. 82

5 Conclusions and Perspectives....................................................................................................... 85
Interdisciplinary Graduate Program: ‘Living Environment North Sea Coast’........................... 88
References ............................................................................................................................................ 89
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