Options we are no longer considering

These are the options we were previously exploring but have now been confirmed to not be taken forward as stand-alone options.

Flood storage

Cross section graphic showing an above ground flood storage area. Water enters through an inlet pipe from the main river. The "normal storage zone" is shown partly filling the area. Water is stored for irrigation or water resource purposes. In the "flood control zone" flood water would only be stored during flooding. Outlet pipes can transport water back to the river or on for use elsewhere.

Above-ground storage: This wouldn’t work well to reduce flood risk because there isn’t enough space available in the project area to hold the large volume of floodwater over a long period. Underground aquifer storage: This isn’t practical because when river levels are high, groundwater levels are also high, leaving little extra storage capacity. It could also increase the risk of groundwater flooding and affect water quality.

Underground aquifer storage: This isn’t practical because when river levels are high, groundwater levels are also high, leaving little extra storage capacity. It could also increase the risk of groundwater flooding and affect water quality.

Natural Flood Management

Graphic depicting natural flood management measures. This is shown as a before and after, where river meanders are restored, green buffer zones implemented next to the river and trees planted. This helps to slow the flow of water into the river, provide new habitats for animals and plants, and make the river channel more structurally stable.

Each action that slows down the water flow or stores water could have a small positive effect on our project area. The more of these actions that are taken, the bigger the impact is likely to be. However, there isn’t enough land available to do so which means it’s not sufficient as a stand-alone option.

The Environment Agency and partner organisations are delivering natural flood management elsewhere and working to change farming practices.

Channel improvements Graphic showing a before and after scenarios of channel improvements. Without channel improvements, low channel capacity can result in less water being moved in the river and a larger flood zone. In the after image, a wider deeper channel results in increased channel capacity results in more water being conveyed and a smaller flood zone.

Dredging is part of options known as channel conveyance improvements, which also include:

Channel widening: This is not practical because there isn’t enough space, as there are buildings on both sides of the river.

Modifying existing structures: We are still looking at this option to support the other options we are considering.

Dredging can increase a river’s ability to convey water by only a modest amount. During flood events, when river conveyance has exceeded the normal channels’ capacity and is using the floodplain to flow, deepening of a river channel often makes little difference to water levels as the amount of water trying to enter the channel far exceeds the small additional capacity dredging would provide (as shown on the picture below).

For dredging to work as a main option, it would need to deepen the river over most of the Datchet to Hythe End stretch and be repeated regularly. This would be very disruptive to river users and residents, extremely expensive, and harmful to the river’s ecosystem.

Cross section depiction of a river channel, flood level, and floodplain. The river channel is not large enough to contain floods, even after dredging. Dredging does not prevent flooding during extreme river flows.

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