Estimating Injury and Loss of Life in Floods: A Deterministic Framework

Abstract

Abstract. This paper presents an outline methodology and an operational framework for assessing and mapping the risk of death or serious harm to people from flooding, covering death and physical injuries as a direct and immediate consequence of deep and/or fast flowing floodwaters (usually by drowning), and deaths and physical injuries associated with the flood event (but occurring in the immediate aftermath). The main factors that affect death or injury to people during floods include flow velocity, flow depth, and the degree to which people are exposed to the flood. The exposure potential is related to such factors as the ''suddenness'' of flooding (and amount of flood warning), the extent of the floodplain, people's location on the floodplain, and the character of their accommodation. In addition, risks to people are affected by social factors including their vulnerability and behaviour. A methodology is described for estimating the likely annual number of deaths/injuries. This is based on defining zones of different flood hazard and, for each zone, estimating the total number of people located there, the proportion that are likely to be exposed to a flood, and the proportion of those exposed who are likely to be injured or killed during a flood event. The results for each zone are combined to give an overall risk for each flood cell and/or community. The objective of the research reported here is to develop a method which could be applied using a map-based approach in which flood risks to people are calculated and displayed spatially for selected areas or communities. The information needed for each part of the process is described in the paper, and the further research to provide the required information is identified.

Methods for the estimation of loss of life due to floods: a literature review and a proposal for a new method

“…The obtained statistical relationships show considerable variation, which might be due to the influence of other factors such as warning, evacuation, flood characteristics and the actual collapse of buildings. Ramsbottom et al (2003Ramsbottom et al ( , 2004, see also Penning-Rowsell et al (2005), developed an approach for assessing the flood risk to people, in a research project for the Environment Agency for England and Wales. The risk to people is determined by three factors: flood hazard, people vulnerability and area vulnerability.…”

“…Five flood events included in the flood fatalities database are investigated. The selected events concern a flash flood (event in Laingsburg South Africa 1984), a coastal flood (Shiranui Town, Japan, 1999) and three river floods in the UK that have been analysed in Ramsbottom et al (2003) and Penning-Rowsell et al (2005). Table 7 compares the results following from the proposed method with observed mortality and fatality numbers.…”

“…high and low danger zones) as a function of water depth and flow velocity. Similarly, Ramsbottom et al (2004) and Penning-Rowsell et al (2005) have proposed a semi-quantitative equation to relate the flood hazard to people to depth and velocity of the water as well as the amount of debris that is in the water. From this equation the level of hazard to people can be estimated and then categorized as 'low', 'moderate', 'significant' or 'extreme'.…”

“…Some authors have investigated loss of life near breaches (see e.g. Tsuchiya and Yasuda 1980;Waarts 1992;Ramsbottom et al 2005). None of the available sources in the dataset relates mortality in the breach zone directly to the local flood characteristics (depth and velocity).…”

A flood vulnerability index for coastal cities and its use in assessing climate change impacts

“…Exposure is generally described as patterns and processes that estimate its intensity and duration (Balica et al 2009). Fekete (2009) describes exposure as the measure of susceptible elements within a region threatened by a hazard, while in Penning-Rowsell et al (2005), exposure is defined as the likelihood that humans and/or physical items (goods, infrastructure, cultural heritage and agricultural fields) will be impacted by flooding. In case of the CCFVI, here exposure is defined as ''the predisposition of a system to be disrupted by a flooding event due to its location in the same area of influence''.…”