2.1 THE FLOOD PROTECTION SYSTEM
Following a period of rainfall, water finds its way through natural or artificially created pathways
to underground aquifers and watercourses which transport it to the sea. Flood management
techniques are used to reduce the risk of flooding during this process. The main techniques for
reducing the risk of flooding to an area can be summarised as shown below:
(i) Hold back some water and let it out at a controlled rate (Flood storage).
(ii) Increase conveyance to get high flows through (Channel improvements/control
structures).
(iii) Divert water around the area (Diversion channel).
(iv) Build flood defences to prevent water getting into protected area (flood
walls/banks).
This guide deals with the reduction of flood risk by preventing the water from getting into the
protected area.
A flood protection system is made up of all the component parts and operational systems that
prevent entry of water onto the protected areas. This includes the barrier superstructure, the
foundation or bedding structure, the seepage cut-off (if applicable), the seals, joints and
interactions within the structure and with the adjacent structures and subsoil. Where
operational activities are required to close up part of a barrier, this forms part of the flood
protection system.
The details of a flood protection system and the critical factors affecting its performance vary
depending on the type of protection system. The different types of flood protection systems
are discussed in Section 2.2.