Coastal Settlements at Risk:
As part of a project called Coastal Settlements at Risk, in September 2002 Ilan Kelman completed his PhD dissertation on Physical Flood Vulnerability of Residential Properties
in Coastal, Eastern England. The dissertation was accepted in February 2003 without any changes required.
A creek flows through a house in Malton, North Yorkshire, on 8 November 2000.
People and Acknowledgements
The project team was:
The project was part of the Cambridge University Centre for Risk in the Built Environment (CURBE) as a joint endeavour between the Martin Centre (Department of Architecture) and the Cambridge Coastal Research Unit (Department of Geography). The entire project was kindly sponsored by Halifax General Insurance Services Limited.
Gratitude is also extended to others who provided further financial support:
Several extreme weather events have caused large-scale losses across the U.K. Examples include the windstorm during the Christmas and New Year period in 1997/98, the floods along inland rivers in central England in April 1998, and the storms and inland floods across the U.K. between October 2000 and February 2001. Each of these events caused several fatalities, damaged hundreds of millions of pounds worth of property, and caused severe disruption to society. History illustrates that many more severe events have occurred in the past and the current state of rapid, global climate change is expected to produce more severe and more frequent extreme events in the future.
Yalding, Kent in southeast England was inundated in autumn 2000.
The east coast of England is particularly vulnerable to storm surge flood events exacerbated by sea-level rise and large-scale land subsidence. East coast storm surges have been extremely devastating in the past, such as the events of 31 January to 1 February 1953 which killed more than 300 people in the U.K. Sea defences in eastern England were raised and strengthened after the 1953 event, but they are nearing the end of their 50-year lifetime. Partly due to the feeling of being protected by these sea defences, coastal development in England has been rapid. The number of people and the value of property highly vulnerable to a major storm surge event in eastern England is far greater than in 1953.
A recent development of bungalows with an ironic name sited just behind the sea defences near Trusthorpe between Maplethorpe and Skegness in eastern England.
This study contributed to the understanding of risks to the built environment from natural hazards by assessing the vulnerability of residential buildings to the hazards associated with a major North Sea storm surge. By combining detailed analysis of the buildings in specific case study sites with sophisticated hydrodynamic modelling of potential storm surge events, the research identified features which determine the vulnerability of residential dwellings to flood damage. Risk management strategies were proposed and decision-making tools were developed.
Case Study Sites
Case study site selection focused on urban sites vulnerable to flooding in coastal, eastern England. Criteria considered included the hydrodynamic environment, the residential building characteristics, the availability of required data, and the disaster history of the location.
The sites chosen were:
Map indicating the case study sites' locations.
Storm Surge Modelling
The research at the Cambridge Coastal Research Unit (CCRU) developed an integrated modelling strategy for the investigation of the physical susceptibility of each case study site to flooding. The model considered the combined effects of astronomical tide, storm surge, wind-wave processes, non-linear interactions and the physical environment of the coastal zone and is capable of representing both the generation of a flood wave and its propagation inland. Flood scenarios were developed for a wide range of meteorological events.
Previous attempts to model coastal flooding have either employed a complex (dynamical) representation of the storm surge with no explicit representation of flooding and drying (operational Storm Surge Models (SSM)) or a dynamical representation of flooding with a simple (statistical) representation of the storm surge (e.g. insurance industry models). Both of these approaches have significant disadvantages. In particular, although operational SSM have provided some useful data on sea state conditions for flood warning and coastal engineering, they remain unsuitable for storm impact studies, which require detailed information about the flood depths and velocities that are likely to be experienced inland. In contrast, while insurance industry models have been designed specifically to predict flood losses in the coastal zone, they have, at best, not been able to fully capture the complex hydrodynamic processes that operate during a storm surge and, at worst, completely ignored the important role of dynamical interactions between floodplain boundary conditions and flow characteristics in determining the propagation of a flood wave. This study focused on circumventing the problems inherent in these traditional approaches, by employing an integrated (linked) modelling strategy, whereby each component of the physical system (storm surge, defence breaches, flood wave) is resolved with an appropriate (numerical or statistical) model.
Output of water depths from a simulated 200-metre sea defence breach in the north of Canvey Island.
Click to access Full results and summaries from this work.
This study demonstrates that significant improvements could and should be made in the manner in which society manages its risk to natural disasters. The focus is on managing the physical vulnerability of residences (houses and flats) to flood disasters in coastal, eastern England. To complement the extensive knowledge of damage from slow-rise flood depth, this study examines the lateral pressure from flood depth differential between the inside and outside of a residence and flood velocity.
To determine the impacts on residences in coastal, eastern England, Canvey Island on the Thames Estuary and Kingston-upon-Hull on the Humber Estuary were selected as case study sites. Field surveys determined characteristics of the physical vulnerability of residences in these locations to floods. A first-order analysis indicated the failure modes of most prominent concern to be analysed in detail:
The observations and calculations were applied to developing a new form of vulnerability profiling: two-dimensional "vulnerability matrices" with flood depth differential along one axis, flood velocity along the other axis, and the matrix cells displaying a damage outcome.
The vulnerability matrices were used to illustrate possible disaster management tools. The "loss equivalent percentage" method of describing quantitative risk was presented for simulated storm surge scenarios on Canvey Island. Qualitative decision-making tools and analysis strategies for residence flood vulnerability management were also discussed.
The results apply specifically to modern residences in England because those were the residences observed in the field surveys. The techniques and methods nevertheless could be used for similar analyses for other locations, other residence types, and other disasters. This study provides new knowledge and methods which contribute to understanding, describing, and managing society’s risk to natural disasters.Click to access Full results and summaries from this work.
Water flowing through a hole in the masonry wall of the flooded wine cellar at Darwin College, Cambridge, U.K.
Download a summary with the title page, abstract, and table of contents (8 pages):
Download an extended summary with a section for each chapter and sample results (22 pages):
Download the entire dissertation (324 pages):
Brickwork wall broken from behind by flood water in Malton, U.K.
Chapter 1: Coastal Settlements at Risk
Chapter 3: Flood Actions on Residences
Chapter 8: Flood Rise Rate Inside a Residence
Chapter 9: Wall Failure
Chapter 11: Flood Failure Flowchart
Chapter 13: Analysis and Application
Sandbags are not a panacea, but might assist, as shown during floods in Cambridge, U.K. in 2001. Here, the sandbag barrier was complemented by pumps and trained personnel on-site for over 50 hours until the river's level diminished.
This project suggested methods for integrated strategies for modelling the physical vulnerability of coastal settlements to storm surge flooding. With the understanding of the losses which could occur for a given event, decision-making techniques for flood management and vulnerability management were suggested and the uncertainties in outputs were analysed.
For further published results and extensions from this work, see Publications on flood issues.
Apparent capillary rise in a flooded house in Keighley, U.K.
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