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| POTENTIAL
IMPLICATIONS OF SHORTLISTED OPTIONS The images below are provided to help you in formulating feedback for all the shortlisted options. The images of No Active Intervention throughout the whole Estuary (Option A) and Hold the Line throughout the whole Estuary (Option C) represent the two ends of the range of options being considered. In addition, an image has been provided of an example of the implications of managed realignment in the Upper and Lower Estuary (Option I). These images present a 'birds eye' view of the Deben Estuary, showing where the high tide and low tide will extend under these options on a day-to-day basis, based on tide levels today. The area covered by the low tide (the blue areas) shows the land that will be underwater at all times. The area covered by high tide (the brown areas) shows the land that will be periodically under water i.e. the intertidal area. These images do not show the extent of flooding that would occur under an extreme event; we will investigate this during the next stage of the study, once we have confirmed which options should be taken forward for detailed assessment. OPTION A – NO ACTIVE INTERVENTION THROUGHOUT THE WHOLE ESTUARY Option A would involve ceasing all maintenance; repair and renewal work on the defences throughout the Deben Estuary. The defences would continue to be monitored and assessed until they eventually failed. Areas of land currently protected from tidal flooding would no longer be protected. Under this option all land would experience intermittent flooding. Due to the reduction in erosion and water speeds in the Upper Estuary there would be a gain of intertidal habitats in front of the defences upstream of Ramsholt. Navigation may become more difficult due to the increased water speeds at the estuary mouth.
OPTION C – HOLD THE LINE THROUGHOUT THE WHOLE ESTUARY This option would involve maintaining and eventually rebuilding the existing flood defences on their current alignment throughout the estuary. Under this option all land and assets would continue to be protected. As sea levels rise, this option would result in an increase in water levels, water speeds and erosion pressure on the defences. The intertidal habitats in front of the defences would also experience increased erosion. To account for the increased pressure on the defences and rise in water levels, the existing defences would need to be raised and strengthened to provide the same standard of protection as today.
OPTION I – MANAGED REALIGNMENT IN THE UPPER AND LOWER ESTUARY This option would involve either naturally allowing the defences to deteriorate or deliberately breaching the defences in a controlled manner. This would result in a change from the current land use at the managed realignment sites to intertidal habitats. Figure 3 shows an example of managed realignment at 2 sites in the Upper Estuary and at Falkenham North Marshes in the Lower Estuary. Managed realignment at selected sites in the estuary could have a combination of effects, such as reducing water speeds, levels and erosion. The overall effect would depend on the number of managed realignment sites.
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