TITLE:
The Value of Using Unofficial Measurements of Rainfall: The Dublin Storm and Flood of June 1963
AUTHORS:
Colin Clark
KEYWORDS:
Raingauge Network, Unofficial Data, Maximum Rainfall Estimation, Dam Safety
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.7 No.2,
February
22,
2019
ABSTRACT: Rainfall measurements are vital for the design of hydraulic structures, climate
change studies, irrigation and land drainage works. The most important
source of design rainfall data comes from convective storms. Accurate assessment
of the storm rainfall requires a fairly dense network of raingauges.
In 1963, such a storm took place over Dublin in Ireland. However, the existing
raingauge network was insufficient to identify both the depth and pattern of
rainfall. An appeal was made by Met Eireann for additional unofficial rainfall
data. The result was remarkable in that the estimated maximum rainfall depth
was found to be more than double the official value and that the resulting
depth area analysis suggested a rainfall volume over a large area much bigger
than the original isohyet map indicated. This result has huge implications for
the estimation of maximum rainfall and dam safety assessment, especially in
countries where the raingauge network has a low density. This paper first
provides a description of the synoptic conditions that led to the storm, second
an analysis of the rainfall data and how the unofficial measurements produced
a very different depth area relationship; third, the social consequences
of the resulting flood are described. Fourth, the storm is then placed in the
context of other storms in the British Isles Finally the implications for rainfall
measurement, gauge density and an example of how revised estimates of
probable maximum precipitation (PMP) have been used to improve the safety
and design standard of a flood detention dam are discussed.