Preventing flooding

Mon, Feb 24, 2014, 01:01

The battering received from winter storms and rain during the past six weeks has brought misery and flooding to many, along with understandable demands that something should be done. In the context of climate change and the prospect of worse weather ahead, issues of affordability, alternative responses and value for money have to be considered. The Government’s newly established Economic and Evaluation Service should play a part.

Arterial drainage has been a vote-getter for political parties and promises to “drain the Shannon” still resonate. Farmers, understandably, are firmly in favour. Drainage was designed to improve agricultural income in river catchments by “carrying away a greater volume of water more quickly”. Effectiveness, however, depended on farmers installing ancillary field drains to reduce water-logging. The only recent assessment of effectiveness, conducted by the Comptroller & Auditor General in 1996, found expected benefits to be less than one-quarter of that projected. An earlier analysis, from the 1960s, concluded the cost of drainage not only exceeded the increase in market value of the benefiting land but, in some cases, exceeded the full post-drainage value of the land itself.

Having drained the major river catchments, the Office of Public Works is required by law to maintain them. A faster water flow tends to displace flooding downstream while increasing silt load, reducing water quality and disrupting the biology of rivers. The construction of towns and housing estates on flood plains has brought horror to many householders. In Ireland, however, nothing has matched the damage caused in England, particularly on the Somerset levels. Here, most arterial drainage schemes were designed to cope with three-year events. Climate change has made that type of planning obsolete. A fresh approach is required, involving legislation, an evaluation of cost effectiveness and a reconciliation of demands from various interests.

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