Issue - meetings
Protecting, Preserving and Promoting the River Itchen in Southampton - Flood Risk Management
Meeting: 19/01/2023 - Scrutiny Inquiry Panel - Protecting, Preserving and Promoting The River Itchen in Southampton (Item 10)
PDF 312 KBReport of the Scrutiny Manager outlining the
focus of the fourth meeting of the inquiry and requesting that the
Panel consider the comments made by the invited guests and use the
information provided as evidence in the review.
Additional documents:
Minutes:
The Panel considered the report of the Scrutiny Manager detailing the issues concerning flood risk management and the River Itchen Flood Alleviation Scheme (RIFAS).
The Panel received the following joint representations from Sam Foulds, Flood Risk Management Team Leader at Southampton City Council; Cara Brims, Flood Risk Officer at Southampton City Council; Blake Jones, Project Executive River Itchen Flood Alleviation Scheme at the Environment Agency; Dave Martin, Flood and Coastal Risk Management Partnership and Strategic Overview Team Leader for New Forest, Test and Itchen at the Environment Agency who summarised the key issues about flooding in Southampton around the River Itchen as:
Tidal Flooding
o The key flood risk is tidal. The Environment Agency is responsible for management of the flood risk from Main Rivers and the sea.
o The greatest risk is to the River Itchen west bank as land levels are lower.
o Southampton has a unique tidal pattern with a double high water – this extends the period where high water may occur with a surge. Rainfall and high tide can cause ‘tide locking’ of surface water sewers.
o Southampton has a number of areas that are vulnerable to flooding with a greater than 0.5% chance of flooding in any given year. The city has been very fortunate that a 0.5% event has not occurred.
o There are currently no formal raised flood defences in Southampton. There is currently a mix of engineered high ground, quay walls, low flood walls and embankments of varying condition and standard of protection.
o Where standard of protection is lower than a potential flood level, water is likely to overtop, resulting in flooding to the ground behind.
o The majority of the Itchen frontage is privately owned – landowners are responsible for maintenance of assets.
o Through the impact of climate change and rising sea levels vulnerability to tidal flood risk will increase over time – more land areas, property and critical infrastructure will become at risk or experience more regular flooding.
o Greatest increase will be seen in Northam and the City Centre – large areas are flat, low lying and reclaimed land.
o Increased risk includes flood extent (areas impacted) and depths of flooding. By 2120, flood depths during a 0.5% AEP (Annual Exceedance Probability) flood could reach up to 1.8m in some areas.
o Southampton Coastal Flood and Erosion Risk Management Strategy (2012) – presents options for management of tidal risk on the west bank of the Itchen Estuary. The Strategy will be delivered in stages over time to create a continuous raised flood defence from Woodmill to Redbridge.
o Focus is on areas where risk and need for defences is greatest:
o Phase 1 – River Itchen Flood Alleviation Scheme (RIFAS).
o Phase 2 – Likely to be Woodmill to St Denys.
o There are plans to revisit the Coastal Strategy to include examination of flood risk on the east bank.
o All new development (including change of use) in a present day or future flood ... view the full minutes text for item 10