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IDENTIFYING THE LONG LIST OF OPTIONS
Initially, a long list of options for the estuary was developed by considering a range of general flood management options that could potentially be applied to any stretch of defence to manage the flood risk in the estuary. These options are: 1. No Active Intervention, 2. Do Minimum, 3. Hold the Line, 4. Advance the Line and 5. Managed Realignment. The General Flood Management Options page discusses each of these options in more detail.
These options form the basic building blocks for developing a strategy for the Estuary. We have
therefore used these building blocks to develop a long list of options for the Estuary, by considering the following:

  • The options of Hold the Line and No Active Intervention each applied across the whole of the
    Estuary;
  • The general flood management options applied to specific locations (flood management units) along the Estuary;
  • The general flood management options in combination with a breach at Slaughden. A breach
    at Slaughden Bend has been considered so that possible scenarios for Slaughden Bend can be
    accounted for in both the Alde and Ore Estuary Strategy and the Thorpeness to Hollesley Coastal
    Strategy.

Given that there are five general flood management options and 15 flood management units within the study area, there are a staggering 30,517,578,125 possible different combinations of options that could be considered for the Alde and Ore Estuary! To develop a more manageable ‘long list’ of options for the Estuary, we therefore used a number of tools including:

  • professional judgement;
  • comments received during the previous round of consultation (Stage 1);
  • preliminary analysis of ‘top down’ modelling results – ‘Top down’ analysis involves using historical patterns of estuary changes to predict what might happen in the long term (50-100 years); and
  • preliminary analysis of ‘bottom up’ modeling results – ‘Bottom up’ analysis involves using a
    computer model built on the existing conditions in the estuary which is used to predict what might
    happen in the short term (0-20 years) to medium term (20-50 years).

We have also divided the estuary into upper, middle and lower ‘sections’ (see Map 1). Rather than model every possible managed realignment site throughout the estuary, we have modelled representative marshes from each of these sections of the estuary.
This allows us to understand how managed realignment at other sites within these sections of the
estuary might affect estuary processes.

Map 1. The Alde and Ore Estuary Study Area

The long list of options for the Alde and Ore Estuary
Table 1 shows the long list of options developed for the Alde and Ore Estuary:

General Flood Management Option
No Active Intervention Options No Active Intervention throughout the whole Estuary
(Maintain Slaughden sea defences)
No Active Intervention throughout the whole Estuary
(No maintenance of Slaughden sea defences)
Hold the Line Options Hold the Line throughout the whole estuary
Hold the Line + Bypass channel across the top corner of Sudbourne Marshes (Ferry Point Corner) by dredging a channel. The purpose of the bypass channel is to force the water to follow the route of the new channel, reducing pressure on the outside bend at Slaughden.
Advance the Line Options Barrier* at Estuary mouth, or upstream at Orford, or at Slaughden
Barrage** at Estuary mouth, or upstream at Orford, or at Slaughden
Managed Realignment + Hold the Line Options Hold the Line + No Active Intervention/ Managed Realignment at one or more sites in the Upper Estuary:
  • Snape Marshes
  • Blackheath Marsh
  • Iken Marshes
  • Hazelwood Marshes
  • Aldeburgh Town Marshes
Hold the Line + No Active Intervention/ Managed Realignment at one or more sites in the Middle Estuary:
  • Sudbourne Marshes
  • Orford Town Marshes
  • Kings Marshes
  • Lantern Marshes
Hold the Line + No Active Intervention/ Managed Realignment at one or more sites in the Lower Estuary:
  • Chillesford Marsh
  • Stonebridge Marsh
  • Chantry Marshes
  • Gedgrave Marshes
  • Boyton Marshes
  • Hollesley Marshes
Managed Realignment + Bypass Channel + Hold the Line options Managed Realignment at Aldeburgh Town Marshes + Bypass Channel across top corner of Sudbourne Marshes (Ferry Point Corner) by dredging a channel + Hold the Line elsewhere
Managed Realignment at Sudbourne Marshes + Bypass Channel across top corner of Sudbourne Marshes (Ferry Point Corner) by dredging a channel + Hold the Line elsewhere
Breach at Slaughden Management Options
Breach at Slaughden + Hold the Line + Open Estuary Mouth
(this option assumes that the existing estuary mouth remains open)
Breach at Slaughden + Hold the Line + Closed Estuary Mouth
(this option assumes that as the breach at Slaughden becomes the dominant mouth for the estuary, the existing estuary mouth closes as a result of natural build up of silt from the coast).
Breach at Slaughden + Managed Realignment at sites in Upper / Middle/ Lower Estuary + Hold the Line elsewhere