IDENTIFYING THE LONG LIST OF OPTIONS
There are thousands of possible permutations of combined estuary options. So, to develop a manageable ‘long list’ of options for the Estuary we have used a number of tools, including:

• professional judgement;
• comments received during the previous round of consultation (Stage 1);
• preliminary estuary modelling including analysis of historical, current and predicted future changes in the estuary.

As a result we have been able to divide the estuary into upper and lower ‘sections’ (see Map 1) based on the characteristics of estuary channel, the flood embankments and the marshes they protect. The Upper Estuary is characterised by a narrower estuary channel with flanking mudflat, saltmarsh and flood embankments protecting relatively small freshwater marshes. The Lower Estuary channel (including the estuary mouth) is characterised by a wider channel and expansive mudflats bordered by flood embankments which offer protection to the extensive and low-lying areas of the Bawdsey, Falkenham and Felixstowe Marshes. Preliminary analysis has shown that whilst the individual management options for the Upper Estuary marshes have little impact on estuary processes, alteration of defences in the Lower Estuary will have more significant impacts.

Rather than model every possible managed realignment site throughout the estuary, we have modelled representative marshes from each of the two sections of the estuary. This allows us to understand how changes in defence alignment at other sites within these sections of the estuary might affect estuary processes.

Widening the estuary mouth has also been given consideration in formulating the long list of options; preliminary analysis of this option shows that the hard defences on either side of the estuary mouth provide an essential control point to the processes within the estuary. Any widening of the mouth would trigger a massive change in the existing dynamics of the estuary which, amongst other effects, would result in the loss of the ‘Knolls’. The Knolls currently reduce water levels within the estuary and feed the down drift coastline with sediment. For this reason, it is proposed that widening of the estuary mouth is only considered as part of a No Active Intervention option, the baseline against which all other options must be compared.

Map 1. The Deben Study Area

The long list of options for the Deben Estuary
Click here to see the long list of options developed for the Deben Estuary.