Hard engineering strategeies are defense schemes that halt a rivers natural processes. They are normally very effective but are expensive and can make flooding worse elsewhere.

Dams (or flood storage reservoirs) - Usually built in upper course. Hold back water in the catchment area. They're effective, can be used to store water, HEP, and control flow of water. Issues involve the removal of settlements and large areas of land are needed. Can alter river ecosystems, and if does flood its severe. 

EXAMPLE: The Three Gorges Dam is thought to have caused the 2008 earthquake.

Straightening (or channel realignment) - Meanders are removed from a river, this means the water has less distance to travel and can therefore be removed quicker. However, it increases erosion and flooding downstream. Straightening increases the rivers efficiencey.

Building up of levees (embankments, flood walls, artificially enhanced levees, revetments) - The levees are widened and heightened to increase the amount of water a river can carry before it floods. They are often enforced with concrete. Flood magnitude may increases due to the increased amount of water held. Increased flooding upstream and downstream, and increased erosion downstream.

EXAMPLE: Mississippi 1993. The levels broke and flooded an area the size of the UK

Diversion Spillways ( includes intercepting channels and flood relief channels) - Floods are directed away from housing and settlements into extra land or channels. However in urban area this isn't possible, and compensation often has to be payed to those who own the land.

EXAMPLE: Garstang. If there is excess water it floods farmland and playing fields.

Channel Enlargement: This is when the river channel is artificially widened and deepened to increases the amount of water it can hold before it floods. Usually occurs in urban areas. It increases the hydraulic radius and so river efficiency. But there is still a risk the river will fill up and flood, especially if the river carries a large load.

N.B. - This has been used at Boscastle to try and prevent future floods.

Flood Proofing - It can be temporary and permanent and involves altering existing structures to make them more resistant to flooding. Potential damage to houses is prevented, it protects houses and possesions and its cheap. However the area will still flood and the damage will be expensive to repair.

EXAMPLE: York. They allow the basements and garages of the houses next to the river to flood.