Poole and Christchurch Bays have a dynamic coastline that requires ongoing management to help reduce flood and coastal erosion risk to communities, infrastructure, and natural habitats.
Our Strategies define what beach works we do, and how we prepare for future climate challenges. On-going monitoring and surveys ensure beach levels are maintained at the correct height and width for coastal defence purposes and trigger maintenance works such as beach recycling or re-profiling if required.
Beach works in Poole Bay and Christchurch Bay
Comparisons are often made between the type and frequency of works carried out in the two bays. However, it’s important to understand that:
- Poole Bay has had an approved Strategy since 2014. This has enabled us to access government funding via Grant in Aid for a timber groyne renewal programme, a beach renourishment programme and the upgrade of Hengistbury Head Long Groyne. For further information:
(a) Poole Bay, Poole Harbour & Wareham FCERM Strategy (pdf)
(b) Poole Bay Beach Management Scheme
- Christchurch Bay lacked an adopted Flood & Coastal Erosion Risk Management Strategy until 2025. Past beach works were mostly funded from council revenue budgets with no means to access national funding. Our new Strategy positions Christchurch Bay to pursue funding on equal footing, though significant local funding contributions will still be required.
We are only able to fund and deliver works agreed within those Defra/Environment Agency approved strategies. Flood and Coastal Erosion Risk Management Grant in Aid funding comes from central government for Capital schemes. These grants are funded based on detailed business cases that build on the strategies, and are developed in line with nationally consistent guidelines and priorities set by central government and administered by the Environment Agency.
Funding cannot be transferred between schemes, and Grant allocated to Poole Bay Beach Management works cannot be spent in Christchurch Bay.
Beach levels and monitoring
We continually analyse sea levels, wave parameters and storm data, as well as monitoring beach levels to ensure our coastline is maintained at the correct height and width. If beach levels were allowed to drop significantly, inshore wave energy would not be attenuated and sea water could run up and over the crest, flooding the areas behind the beach. Low beach levels would also cause the sea wall to be undermined, leading to sea wall failures or collapse and ultimately, the erosion of the cliffs would accelerate. Our modelling suggests this would be by up to 1m per year in some places.
To help inform our decisions, and to monitor beach levels, a range of activities are carried out including:
- Routine Surveys: The Channel Coastal Observatory (CCO) surveys beach profiles every spring and autumn to track changes in beach shape and volume. Results are available at www.coastalmonitoring.org
- Additional Surveys & Inspections: In between the regular CCO surveys we carry out our own additional surveys to better understand beach changes; we also conduct regular visual checks of beach levels, especially near sea walls and groynes. These happen monthly in winter and every two months in summer.
- Storm Impact Surveys: After major storms, we conduct extra inspections and surveys to assess beach damage and recovery.
- Aerial Photography & LiDAR: We use drones to take Aerial and LiDAR surveys. These are flown at specified time intervals to capture all relevant data for our beaches and assets.
- Bathymetric Surveys: Underwater surveys help track how sediment moves offshore. These are carried out regularly by the CCO and are supported by seabed sampling to understand sediment transport via natural processes such as long-shore drift.
Beach profiles
Beaches reshape with the seasons and how noticeable this is can depend on the weather and tides. Generally, during the winter months, waves are more energetic and the finer sand is moved off shore to form sand bars. This makes the beach look lower than usual and with the finer sands gone, the larger beach material such as shingle is exposed and is more noticeable. Generally, during the summer months, the finer sandy material is brought ashore once again by the gentler waves and a wide berm builds up near the shoreline so the beach appears higher.
Beach renourishments
As well as the beach profiles changing, due to natural processes, long-shore drift also transports beach materials from west to east. This process of longshore drift means we loose approx. 70,000 m³ of sand each year from our beaches along Poole and Bournemouth.
If monitoring results show beach levels are getting too low to provide an effective coastal defence, we will seek to carry-out a beach renourishment or beach recycling (subject to funding). The survey data is used to calculate how much sand is needed and to confirm how much is placed.
Beach nourishment works at Poole Bay (Sandbanks to Southbourne) have, since 1970, required placing the equivalent of about 70,000m³ of imported material onto beaches due to the high natural drift rates and mainly sand content (which washes away faster than gravel or mixed beaches). This creates obvious logistical and environmental challenges which we manage as best we can.
Beach recyling
Christchurch Bay is different in that the beach material (which is mostly coarser than in Poole Bay) is recycled. This is because survey data (since 2003), shows that much of the material at the Bournemouth end of Christchurch Bay, has remained in the system and can be moved around locally to save on unnecessarily bringing in new sediment. Both bays are afforded protection from the long groyne at Hengistbury Head (and other smaller structures) and the complex ebb delta at Christchurch Harbour entrance.
Beach recycling works with the natural process of longshore drift. This involves collecting material from areas where it has built up and moving it to the depleted beach areas. If the system (ie the beaches from the harbour to Highcliffe) did show an overall drop in volume (as we can quantify from our regular surveys), we would consider ways that we could bring in new material – however this is not guaranteed as we would be bound by strict central government funding and environment rules. Currently the cost/benefit scoring (mainly weighted by residential property at risk) would not enable works in Christchurch Bay on the same scale as in Poole Bay.
Coastal asset inspections
Ongoing checks of coastal defences including seawalls, groynes and other structures such as gabion baskets ensure that they continue to perform effectively, and maintenance requirements are flagged. We also ensure that aids to navigation are monitored and repaired in line with legal requirements assessed by Trinity House.
- Read more about our Asset Maintenance projects including aids to navigation