Improving performance targets for flood defence assets

Abstract

The Environment Agency manage over 10 000 km of raised flood defence assets (embankments, walls and structures) in England and Wales. These assets are managed to minimum targets that are expressed as a condition grade: a number between 1 (Very Good) and 5 (Very Poor) that is determined by visual inspection according to the Condition Assessment Manual. This paper discusses the good performance of the defences during the flood events of summer 2007: 1000 km of defences were tested, about 500 km was overtopped, but only four breaches occurred. The events have also shown that breaches can have various causes and that condition grade is only one indicator of performance. The paper then presents an analysis of the fragility of defences leading to the conclusion that in most cases, lower minimum condition grades are acceptable. This should enable more effective use of limited available funds, for example for data collection, analysis or improvement works.

Coastal Flooding in the Solent: An Integrated Analysis of Defences and Inundation

“…Crest heights were mostly from real-time kinematic (RTK) GPS surveys with a vertical accuracy of ±0.03 m [46]. Recent condition grade scores (between 1 for excellent, and 5 for poor) were supplied by local authorities, allocated by coastal engineers to defences in England and Wales during routine inspections, and which can be mapped to defence performance under loading [61,62]. Figure 5.…”

A framework for valuing the human dimensions of engineered systems

“…The characterisation of the performance of engineering assets is often supported by some form of simple scoring system (Hooper et al, 2009, 73-76) to grade the structural condition of their assets, such as the five point visual inspection scale (Table 1) used by the Environment Agency (Flikweert and Simm, 2008). Such scales are used to capture deterioration in asset condition and improvements delivered by management action.…”

Flood risk assessment for infrastructure networks

“…For instance, an asset may be affected because of the flooding of a remote but physically associated asset, for example because of widespread loss of power after the flooding of key points in the national grid, as occurred in Gloucestershire in the summer of 2007 (Pitt, ). While frameworks are in place for assessing flood risk, including systems of flood defence assets (DEFRA/EA, ; Dawson et al ., ; Dawson and Hall, ; Flikweert and Simm, ), these methods cannot be easily extended to cases where the physical interdependence of assets is the essence of the problem.…”