Rainfall
Return Periods Table
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- Information on the frequency of heavy rainfalls is often required
by engineers, architects and others, usually in connection with
design criteria for water management or drainage schemes. In most
cases it would be uneconomic to construct a system capable of coping
with the most extreme rainfall possible, even if the magnitude of
this is known. Instead, it is usual to design the system so that
it will be capable of accommodating a rainfall likely to be exceeded
only once in a specified number of years (return period).
- A depth duration frequency model allows for the estimation of
point rainfall frequencies for a range of durations for any location
in Ireland. The model consists of an index (median) rainfall and
a log-logistic growth curve which provides a multiplier of the index
rainfall. Rainfall station data were analysed and an index
rainfall extracted. Computer applications were written to apply
the model and produce outputs of the return period rainfalls.
- The set of parameter values summarising the rainfall Depth-Duration-Frequency
(DDF) relationship enables the production of consistent estimates
of point rainfall frequencies over durations ranging from 5 minutes
to 25 days. These estimates supersede those provided in Logue (1975).
- The model enables the estimation of rainfall frequencies at any location. Rainfall Return
Period tables are now freely available by submitting the form below.
Method used in the Estimation of Point Rainfall Frequencies
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