Winter preparation

Why flooding happens

Flooding happens when water cannot drain away quickly enough. This can happen when the amount of water exceeds the capacity of the drainage system or when drainage routes do not work effectively. Common causes include:

• intense or prolonged rainfall
• blocked gullies, pipes, ditches or culverts caused by silt, leaves, debris or vegetation
• damaged drainage assets, such as collapsed pipes or defective outfalls
• watercourses that cannot carry water away efficiently
• high groundwater levels, which reduce the amount of water the ground can absorb
• increased areas of hard surfaces, such as roads and buildings, which create more surface water runoff
• extreme weather events that produce more rainfall than drainage systems are designed to manage

Flooding often results from a combination of factors rather than a single issue.

Further information is available on our flooding advice page.

Why water around a drain does not always mean it is blocked

Water around a drain does not necessarily mean there is a blockage.

During extreme rainfall, more water can fall on the highway than the drainage system can carry away, even when it is working as designed.

Some gullies may also appear full because they connect to soakaways elsewhere in the drainage network. These soakaways need time to absorb and disperse water into the surrounding ground.

Highway drainage

Highway drainage systems collect surface water from roads and carry it away safely. This helps reduce flood risk and improves road safety.

The drainage process works as follows:

• rain falls onto the road surface
• the road's camber and gradients direct water towards the kerb
• water enters gullies through roadside gratings
• gullies connect to underground drainage pipes
• the pipes carry water to a suitable discharge point

Water may discharge to:

• a ditch, stream or river
• a soakaway, where the water absorbs into the ground
• a surface water sewer network
• an attenuation feature or balancing pond

Drainage maintenance

Our drainage teams carry out proactive gully cleansing at high-priority sites before winter.

We have identified around 400 drainage assets across 63 sites for maintenance. This work helps water flow through the drainage network and reduces the risk of localised flooding during periods of heavy rainfall.

Temporary traffic management may be in place while we carry out this work.

Responsibilities

West Sussex County Council are responsible for highway drainage and road flooding associated with surface and ground water. See how to report a problem with flooding, blocked drains and gullies.

District and borough councils are responsible for some flood-risk functions and local support. Find your local district or borough council.

The Environment Agency are responsible for main rivers and sea flooding. Contact the Environment Agency.

Water companies are responsible for public sewers. In West Sussex, these are:

• Portsmouth Water
• Southern Water
• South East Water

Riparian owners are responsible for watercourses on or adjacent to their land or property.

Riparian ownership

If your property or land borders a river, stream, ditch or culvert, you may be a riparian owner. As a riparian owner, you are responsible for helping to maintain the watercourse and keeping it free from blockages. This helps reduce the risk of flooding to people, property and the environment.

Find guidance on managing flood risk and riparian ownership.

How you can help

Residents can play an important role in reducing flood risk by:

• putting litter in bins to prevent drains and gullies becoming blocked
• keeping garden waste, leaves and grass cuttings off roads and footways
• clearing leaves and debris from private driveways, ditches and drainage features where safe to do so
• reporting persistent flooding or blocked drainage assets to the county council
• checking local flood alerts and preparing your property in advance of severe weather

Snow and ice

Everyone can help improve winter resilience by:

• supporting parish and town council winter initiatives
• taking part in local winter plans and community response arrangements
• volunteering to help vulnerable neighbours during severe weather
• working with local farmers and community groups who assist with snow clearance when conditions are particularly challenging
• preparing ahead by keeping essential supplies at home and planning journeys carefully during winter weather