RMS Finds Repeat of 1607 Floods Could Cost UK Insurers $25.5 Billion

January 30, 2007

Newark Calif.-based Risk Management Solutions has issued a study, which concludes that, a “repeat of the tide and wind-driven storm surge that caused the Bristol Channel floods of 1607 would result in the U.K.’s costliest natural disaster.” The study, which was issued to coincide with the 400th anniversary of the1607 disaster, “shows that insured losses from a modern day repeat of the conditions that led to the floods potentially could be up to £13 billion [$25.5 billion] for the worst case scenario.”

RMS said that “over 80 percent of the total losses from the same floods today would occur in the inner Bristol Channel, including the cities of Bristol, Cardiff and Gloucester, with the remaining losses along the southwestern coast of Wales, and around Barnstaple in Devon. The study estimates that an event of the magnitude of the 1607 floods occurs about every 500 to 1000 years, on average.”

RMS calculated that between “500 and 2000 people were killed by the flooding on 30 January 1607 in villages and farms along the low-lying coastlines around the Bristol Channel and Severn Estuary.” It said that, although some reports have speculated that a tsunami may have caused the floods, “recent research confirms that the cause was a major storm surge created by persistent gale force winds and low air pressures, coupled with an exceptionally high tide.

“A similar combination of factors today could raise water levels up to 9.5 meters [almost 31 feet] above sea level in the inner Bristol Channel.” Such a flood would overtop current flood defenses and submerge hundreds of square kilometers of coastal floodplain around the Bristol Channel and Severn Estuary of southwest England and south Wales.

RMS also noted that “high tide levels in the region have risen by more than a meter [3.25 feet] in the past 400 years, mainly due to a rise in relative sea level, so flood waters from the same event today would significantly exceed the high water marks recorded in 1607.”

The potential cost of a repeat of the 1607 Bristol Channel floods, up to £13 billion, “would be even greater than the £7 billion [$13.77 billion] in damage that it is estimated would result from a repeat of the 1953 floods along the east coast of the UK,” RMS concluded.

“It is well-known that the east coast of Britain is vulnerable to a storm surge flood, and flood defenses have been significantly upgraded since the catastrophic flooding of 1953,” noted Dr. Robert Muir-Wood, chief research officer of RMS and a co-author of the report. “This study shows that storm surges also pose a potentially catastrophic risk to the West Coast of Britain. Current flood defenses might protect areas from a storm surge of up to 8.5 meters [27.6 feet], but would not be able to contain a truly exceptional event on the scale of the 1607 floods.”

He added that, “although the risk of a repeat of the 1607 floods is comparatively low, it is not negligible.”

RMS also explained that the high tide on January 30, 1607 “was exceptional because the semi-diurnal tidal forces were at their most extreme, with the sun and moon both overhead at the equator and the moon at its closest to the Earth.”

Such tides, however, while infrequent, are not unusual. RMS said such “extreme tidal forces are estimated to occur about every 4.5 years.” The next such tide is expected on March 20, 2007.

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