Flood hazard assessment for extreme flood events

Davor Kvočka,Michaela Bray,Roger A Falconer

doi:10.1007/s11069-016-2501-z

Abstract

Climate change is expected to result in an increase in the frequency and intensity of extreme weather events. In turn, this will result in more frequent occurrences of extreme flood events, such as flash flooding and large-scale river flooding. This being the case, there is a need for more accurate flood risk assessment schemes, particularly in areas prone to extreme flooding. This study investigates what type of flood hazard assessment methods should be used for assessing the flood hazard to people caused by extreme flooding. Two flood hazard assessment criteria were tested, namely: a widely used, empirically derived method, and recently introduced, physically based and experimentally calibrated method. The two selected flood hazard assessment methods were: (1) validated against experimental data, and (2) used to assess flood hazard indices for two different extreme flood events, namely: the 2010 Kostanjevica na Krki extreme river flood and the 2007 Železniki flash flood. The results obtained in this study suggest that in the areas prone to extreme flooding, the flood hazard indices should be based on using the formulae derived for a mechanics-based analysis, as these formulations consider all of the physical forces acting on a human body in floodwaters, take into account the rapid changes in the flow regime, which often occur for extreme flood events, and enable a rapid assessment of the degree of flood hazard risk in a short time period, a feature particularly important when assessing flood hazard indices for high Froude numbers flows.

Highlights

Flooding is the most frequently occurring natural disaster in the world (Jonkman 2005)
The results obtained in this study suggest that in the areas prone to extreme flooding, the flood hazard indices should be based on using the formulae derived for a mechanics-based analysis, as these formulations consider all of the physical forces acting on a human body in floodwaters, take into account the rapid changes in the flow regime, which often occur for extreme flood events, and enable a rapid assessment of the degree of flood hazard risk in a short time period, a feature important when assessing flood hazard indices for high Froude numbers flows
The two flood hazard assessment methods considered were first evaluated against three different experimental datasets, including two datasets based on testing real human subjects and one dataset based on experiments using model human bodies, and later used to assess the flood hazard rating for two extreme flood events, i.e. the 2010 Kostanjevica na Krki extreme river flood event and the 2007 Zelezniki flash flood

Summary

Introduction

Flooding is the most frequently occurring natural disaster in the world (Jonkman 2005). It is expected that flooding is going to occur even more frequently in the future as a result of climate change (Lenderink and Van Meijgaard 2008; Min et al 2011; Rojas et al 2013; Bruwier et al 2015). As well as the expected increase in the magnitude and frequency of future flooding, there will be an increase in the world’s population from the current level of 7.3–9.7 billion by 2050 (UN 2015). It is projected that 66 % of the world’s population will live in urban areas by 2050 (UN 2014), while in the near future 40 % of the global urban land will be located in areas highly prone to flooding (Guneralp et al 2015). The number of people affected annually by flooding will almost certainly increase significantly in the future

Objectives

Methods

Results

Conclusion