FLOODING- Flood prediction

Flood prediction

Hydrologists = try to forecast the likelihood of futrue flood events using past records. 

Data = river discharge records - precipitation + flood recurrence interval graphs.

These graphs = calculate statistically the probability of flooding in the future based on past records.

The further back flood records go = more accurate the prediction.

Records of a river's discharge are ranked - longest period available,from highest peak discharge to the lowest recorded. 

The following formula is used to calculate the recurrence interval:

recurrence interval (years) = number of years on record +1 / ranking of flood being considered

When the recurrence interval = plotted against discharge as a scatter graph on semi-logarithmic graph paper,

= possible to use the line of best fit to predict when the next flood of a particular magnitude might occur

= flood return period. 

The Department for Environment Food and Rural affaris (DEFRA) and the Environment Agency 

=  main organisations responsible for flood management of major rivers

E.G Thames and the Severn in the British Isles 

Use flood recurrence interval graphs to plan flood defence strategies.

Densely populated urban areas = sufficiently protected against a 1 in a 100 year flood events 

Grassland and low productivity agricultural land should not be protected at all.

Hydrologists use past data records showing: 

The regime or yearly pattern of discharge in relation to annual precipitation patterns

= likelihood of seasonal flooding can be assessed.