6.2 Integrated Estuary Management
147
of the European Water Framework Directive and, of course, prior to that over decades
based on the development in Member States.
The main issues in estuaries are the tidal amplification together with morphological
changes and salt water intrusion, as it has been identified in the EMOVE project – see also
Gregory (2006); Ducrotoy (2010) and EMOVE Project Consortium (2015a). Therefore,
selected approaches will be provided on how estuarine managers or administrative bodies
are trying to deal with these challenges. The ideas to counteract tidal amplification of an
estuary will be exemplified for the Elbe river. Tidal range doubled (tidal gauge St. Pauli)
since human interference in the river Elbe started, and the tidal characteristic is disturbed.
The flood current is stronger than the ebb current resulting in a net import of sediment into
the estuary. Dredging is essential in estuaries to keep the fairway to the desired draft. Thus,
the dredged sediment has to be handled either by extracting it from the river system or relocating it within the system. Different approaches exist depending on the characteristic
and the shape of the estuary. Here, the example of the Schelde river will illustrate that
traditional sediment management, that is, dredging and disposal of the material outside
the system, might show undesirable effects. Deepening and straightening of river channels
led to an increased flow velocity, hence, to an upstream shift of the brackish water zone.
Different types of land use adjacent to the estuary may depend on fresh water abstraction
from the river. If the brackish water zone is moving upstream abstraction of fresh water
might be limited or impossible. The situation of salt water intrusion, the consequences and
possible solution options will be exemplified for the river Weser in Germany.
6.2.2 Ideas to Influence Tidal Amplification
Over centuries the way of adapting rivers to an increasing demand by transport was
deepening and straightening of river channels (see Sect. 5.4.3 and Fig. 5.22). As major
consequence tidal range increased up to twice as high as it was under natural conditions.
Furthermore, the normally ebb-dominated turned to flood-dominated estuaries which
means that sediment is imported into the upper reaches of the river. For example, the harbor of Hamburg suffers sedimentation of fine grained material in the harbor area (Fig. 5.33)
which lead to the reduction of the possible draft and worsened the turbidity of the water
column. Instantaneous measures were and still are high efforts in maintenance dredging
and the implementation of artificial river conservancy measures. The closure of former
tributaries to the Elbe river and side channels aimed at concentrating the current in the
fairway and to increase the flow velocity for an aspired self-sustaining effect. Finally, the
current cross-section of a river looks like shown in Fig. 5.22 (bottom). Continuously high
efforts and to some extend an even increasing demand in dredging result in developing
new ideas and to some extend to scrutinize the existing measures.
Today, the way of dealing with estuaries is to almost return to the picture like in
Fig. 5.22 (top) shown. The width of the cross section should be enhanced rather than the
draft should be reduced, because container vessels show a constantly increasing size. Dike
relocation where possible and feasible and the re-connection of former side channels are
147
of the European Water Framework Directive and, of course, prior to that over decades
based on the development in Member States.
The main issues in estuaries are the tidal amplification together with morphological
changes and salt water intrusion, as it has been identified in the EMOVE project – see also
Gregory (2006); Ducrotoy (2010) and EMOVE Project Consortium (2015a). Therefore,
selected approaches will be provided on how estuarine managers or administrative bodies
are trying to deal with these challenges. The ideas to counteract tidal amplification of an
estuary will be exemplified for the Elbe river. Tidal range doubled (tidal gauge St. Pauli)
since human interference in the river Elbe started, and the tidal characteristic is disturbed.
The flood current is stronger than the ebb current resulting in a net import of sediment into
the estuary. Dredging is essential in estuaries to keep the fairway to the desired draft. Thus,
the dredged sediment has to be handled either by extracting it from the river system or relocating it within the system. Different approaches exist depending on the characteristic
and the shape of the estuary. Here, the example of the Schelde river will illustrate that
traditional sediment management, that is, dredging and disposal of the material outside
the system, might show undesirable effects. Deepening and straightening of river channels
led to an increased flow velocity, hence, to an upstream shift of the brackish water zone.
Different types of land use adjacent to the estuary may depend on fresh water abstraction
from the river. If the brackish water zone is moving upstream abstraction of fresh water
might be limited or impossible. The situation of salt water intrusion, the consequences and
possible solution options will be exemplified for the river Weser in Germany.
6.2.2 Ideas to Influence Tidal Amplification
Over centuries the way of adapting rivers to an increasing demand by transport was
deepening and straightening of river channels (see Sect. 5.4.3 and Fig. 5.22). As major
consequence tidal range increased up to twice as high as it was under natural conditions.
Furthermore, the normally ebb-dominated turned to flood-dominated estuaries which
means that sediment is imported into the upper reaches of the river. For example, the harbor of Hamburg suffers sedimentation of fine grained material in the harbor area (Fig. 5.33)
which lead to the reduction of the possible draft and worsened the turbidity of the water
column. Instantaneous measures were and still are high efforts in maintenance dredging
and the implementation of artificial river conservancy measures. The closure of former
tributaries to the Elbe river and side channels aimed at concentrating the current in the
fairway and to increase the flow velocity for an aspired self-sustaining effect. Finally, the
current cross-section of a river looks like shown in Fig. 5.22 (bottom). Continuously high
efforts and to some extend an even increasing demand in dredging result in developing
new ideas and to some extend to scrutinize the existing measures.
Today, the way of dealing with estuaries is to almost return to the picture like in
Fig. 5.22 (top) shown. The width of the cross section should be enhanced rather than the
draft should be reduced, because container vessels show a constantly increasing size. Dike
relocation where possible and feasible and the re-connection of former side channels are