Storm Surges Flashcards
What is a surge?
An elevation of water levels above those predicted for the tide
What are the two factors that combine to create a storm surge?
Low Pressure and Strong Onshore Winds
What does a residual represent and when will it be worst?
Difference in predicted and observed tide. Most damaging at High Water and on a Spring Tide
List four years in which there have been recent damaging storm surges?
2014
2013
2010
2008
What is the greatest factor in elevating sea surface?
Wind Stress
If pressure was to change by 100 hPa by how much would sea level rise?
1cm
A deep depression has a pressure of 970 hPa, how much would sea level rise?
42cm
If the wind speed is 40 knots how much stress is produced?
0.9 N / Metre Sq.
What two factors affect the nature of a surge?
The wind pressure field and local topography
In the North Sea by how much would the water level be elevated by during a Northerly gale?
1.3m
5 facts about the 1953 North Sea storm surge
- A deep depression moved down the North Sea at the same rate as the HW Spring Tide and a Northerly wind
- Elevation of 1.7m above the predicted
- Coriolis moved water towards the coast, it became trapped and a kelvin wave was produced
- More than 1000 deaths
- Lead to the London Flood Defences
Which storm surge event in the Bristol Channel cause speculation as to whether or not it was caused by a tsunami?
1607
What was the residual at Avonmouth and the predicted HW on 13th Dec. 1981?
Residual - 1.89m
Predicted - 8.75m AOD
During the 1981 storm what acted as an inland barrier to reduce the impact to the Somerset levels?
The M5 embankment
What affect did the South Easterly winds have during the 1981 storm?
They evacuated water from Bridgewater bay, creating a bulge in Carmarthen Bay, which was carried at the same time as the tide up the channel
