Flood plains are areas that can be overwhelmed by flood. Though not a regular occurrence, when flooding occurs, which chiefly involves rising of a river above its elevation (flood stage), it causes a lot of damage beyond its banks. Generally, it is advisable should not be constructed around flood plains. However, if risk to life of such areas and social and economic considerations justify the construction of buildings at around flood plains, the following points are worthy of note:
1. If there are high areas around the flood plains, preferably cluster the buildings around the high areas.
2. If high areas are not available, one may build up an earth fill, stabilize it and erect the building on it, ensuring that the earth fill embankments are protected against erosion by water.
3. Alternatively, one may raise the building on stilts (columns in an unclosed space) while ensuring that these stilts and utilities are adequately protected against damage from flood flows.
4. If the options 1 to 3 above are not feasible, the following measures should be taken for buildings at flood plains:
a. Buildings at flood plains should be furnished with impervious exterior.
b. Windows in the buildings should be above flood stage or level.
c. Doors in the buildings should be sealed tightly against the frames.
d. Generally all openings, where applicable, should additionally be protected with flood shield such as wall or movable flood shield especially when flood are imminent.
e. Mechanical and electrical components should be located above the flood level.
f. There should also be electric generators to provide emergency power when desirable.
g. Pumps should be installed to eject water that leaks into the building.
h. Emergency water supply should be stored in tanks above flood level and cutoff valves should be provided with the sewerage system to prevent backflow.
Merrit, F.S. and Ricketts, J.T. (2000). Building Design and Construction Handbook (6th edition). McGraw Hill, London.