2008 Morpeth Flood

2008 Morpeth floods

Telford Bridge at 1332 BST on 6 September 2008.
Date	6 September 2008
Location	Morpeth, Northumberland, England
Deaths	none
Property damage	approx. £40 million

The 2008 Morpeth floods occurred on Saturday, 6 September 2008 in Morpeth, a town in Northumberland, northeastern England, when, following sustained heavy rainfall during the previous twenty-four hours, the River Wansbeck burst its banks and overwhelmed the town's flood defences. Nearly one thousand properties, mostly residential, were damaged.

Previous flooding events occurred in 1863, 1876, 1877, 1878, 1881, 1886, 1898, 1900, 1903, 1924, 1963 and 1968 (Cotting Burn).

In 1992, a record peak water level of 3.19 metres (10.5 ft) was recorded in the river channel. The 2008 flood level was 0.8 metres higher than this. However, there was not a flood event in 1992 as the defences successfully protected the town centre.

The low pressure "Mattea" formed at the southern tip of Greenland on September 3, deepening to approximately 980hpa as it passed to the south of Ireland on September 5. The low then remained in place over the UK before dissipating on September 9. An occluded front associated with this low moved slowly north across the UK producing flash flooding across the Midlands and the North. The Environment Agency recorded 150 millimetres (5.9 in) of precipitation falling in the Wansbeck catchment area between Friday 5 and Saturday 6 September. Figures suggest that in Morpeth alone there was 86 millimetres (3.4 in) of rain compared to an average of 74 millimetres (2.9 in) for a month. Environment Agency statistics show that it was a unique event as peak river discharge was the highest that had ever been recorded.

The River Wansbeck Valley is narrow and steep and as a consequence has exaggerated amounts of surface runoff. Based on three storm events, a reliable flow gauge located upstream of Morpeth at the confluence of the Wansbeck and Font showed that 56% of rain fall is converted into surface runoff. Because the soil was already saturated as a result of the wet summer, the effect of surface runoff was greatly enhanced. Furthermore, increased urbanisation since the 1960s in Morpeth meant that most water falling on the town would have drained directly to the river channel. Other tests investigating the catchment lag time (time lapse between the midpoint of storm rainfall and peak river level) indicate that the Wansbeck has a LAG time of only 8 hours. This means that any water falling in the catchment area would have been rapidly converted into channel flow by surface runoff and to a lesser extent by throughflow. This is due to the steepness of the valley and the soil composition.