Flood Prediction and Flood Return periods

Year 12 geography GCE

Flood Prediction?

Hydrologists try to forecast the likelihood of future flood events using pastrecords. The further back the records of the floods go, the more accurate theprediction.

Records of river discharge are ranked over the longest period available, from thehighest peak discharge to the lowest peak discharge. The following formula isthen used to calculate the recurrence intervals

When the recurrence interval is plotted against discharge as a scatter graph onsemi –logarithmic graph, it is possible to use the line of best fit to predict whenthe next flood of a particular magnitude might occur. This is called the floodreturn period.

Look at the graph below. What would the flood return period be for a discharge10,000 and 5,000 cumecs?

Using the formula, calculate flood return period for the discharge recorded in1997 and 1955 for the East Fork of the Carson River. The recording period was200 years.