Floods of information

I HAVE heard it claimed in the early hours of April that the science of hydrology takes its name from the 19th century archaeologist…

I HAVE heard it claimed in the early hours of April that the science of hydrology takes its name from the 19th century archaeologist, Godolphus Hyde.

By dint of careful excavation, Hyde assembled a series of monthly rainfall charts for Lower Mesopotamia for 2348 BC, and discovered a clear maximum in late November, thereby establishing the precise date of Noah's flood.

But, of course, Godolphus never was. Hydrologists owe the label of their calling to the Greek word hudor, meaning water; hydrology concerns itself with where it comes from, where it goes and how it gets there, and tries to explain such happenings as

Contagious fogs, which falling on the land

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Have every pelting river made so proud,

That they have over borne their continent.

Flooding, as we know from several nasty incidents in recent years, is a problem often caused by the inability of a river to cope with an unusually large amount of water. There are ways of avoiding such eventualities: the channel available to the river can be enlarged; alternative routes, like underground pipes or surface canals, can be provided at critical points to allow passage to the excess water; or sometimes it may be feasible to build embankments to hold back the flood waters from vulnerable areas.

But all these possibilities [have one thing in common: they are very expensive. Moreover, the best solution, if there is one, depends on the scale of the problem - on the typical amount of water to be coped with when a flood occurs, or on the frequency with which an inundation of given proportions comes along.

Engineers can use statistical methods to estimate these risks. When the ups and downs of the daily volume of water in a river have been accurately measured over a long period, it is possible to calculate the rate of flow which will be exceeded, on average, only once every 10 years, every 100 years, or any other length of time you care to think of.

"Return periods" as these are called, and related matters, are likely to feature in a lecture by Dr Michael Bruen of the Water Resources Centre of UCD, scheduled for 8 p.m. tomorrow, Friday evening.

The talk is organised by the Irish Meteorological Society, and is entitled A Hydrologist's Perspective on Floods, the venue being Earlsfort Terrace premises of UCD. As is usual on such occasions, all who have a wish to go along are more than welcome.