Modelling the benefits of flood emergency management measures in reducing damages: a case study on Sondrio, Italy

Abstract

Abstract. The European "Floods Directive" 2007/60/EU has produced an important shift from a traditional approach to flood risk management centred only on hazard analysis and forecast to a newer one which encompasses other aspects relevant to decision-making and which reflect recent research advances in both hydraulic engineering and social studies on disaster risk. This paper accordingly proposes a way of modelling the benefits of flood emergency management interventions calculating the possible damages by taking into account exposure, vulnerability, and expected damage reduction. The results of this model can be used to inform decisions and choices for the implementation of flood emergency management measures. A central role is played by expected damages, which are the direct and indirect consequence of the occurrence of floods in exposed and vulnerable urban systems. How damages should be defined and measured is a key question that this paper tries to address. The Floods Directive suggests that mitigation measures taken to reduce flood impact need to be evaluated also by means of a cost–benefit analysis. The paper presents a methodology for assessing the effectiveness of early warning for flash floods, considering its potential impact in reducing direct physical damage, and it assesses the general benefit in regard to other types of damages and losses compared with the emergency management costs. The methodology is applied to the case study area of the city of Sondrio in the northern Alpine region of Italy. A critical discussion follows the application. Its purpose is to highlight the strengths and weaknesses of available models for quantifying direct physical damage and of the general model proposed, given the current state of the art in damage and loss assessment.

Coping with Pluvial Floods by Private Households

“…In the context of pluvial floods, emergency measures are expected to play an important role in damage reduction, as typically lower water levels compared to fluvial floods are assumed to make these measures particularly effective. However, the effectiveness of a particular measure in terms of damage reduction depends on a large number of factors, including the type of warning, lead time, the person implementing the measure, etc., and is still hardly understood [52]. For this study, the flood affected households in Lohmar, Hersbruck and Osnabrück were asked to report on the emergency measures they had undertaken and how they assess the effectiveness of these measures in order to reduce damage.…”

Quantification of flood risk mitigation benefits: A building-scale damage assessment through the RASOR platform

“…Accurate estimation of flood 5 impacts is crucial to quantify the actual risk and evaluate the cost-effectiveness of hydraulic mitigation works (Förster et al, 2005;Gouldby et al, 2008;Shreve and Kelman, 2014), which require significant investments. Flood impacts estimates are also crucial for non-structural mitigation measures, such as emergency management (Molinari et al, 2013). A deep understanding of flood risk and pos-10 sible mitigation strategies is unavoidable to communicate technical findings to institutions and firmly support political decision making (Murnane et al, 2016) .…”

New insights into flood warning reception and emergency response by affected parties

“…Handmer et al, 1988;Thieken et al, 2005a;Meyer et al, 2012;Molinari et al, 2013). However, empirical studies on the effectiveness of early warning and emergency response are rare.…”

“…One early exception is provided for the flood in Lismore (Australia) in 1974: with a lead time of about 12 h, damage in the residential sector was only 50 %, and in the commercial sector it was only 24 % of the economic damage expected without emergency measures (Smith, 1981). Another example is early warning and response to flash floods in the city of Sondrio, Italy: there it is estimated that responsive action led to a damage reduction of about 10-25 % (Molinari et al, 2013).…”

“…Important factors influencing the effectiveness of emergency response in reducing damage are the lead time, the flood intensity and the ability of civil protection and affected parties to undertake emergency measures effectively (Handmer et al, 1988;Penning-Rowsell and Green, 2000;Kreibich et al, 2007a;Molinari and Handmer, 2011;Molinari et al, 2013;Mross et al, 2016). The longer the lead time, the longer the time for undertaking emergency measures.…”