Material damage caused by high-magnitude rainfall based on insurance data: Comparing two flooding events in the Lisbon Metropolitan Area and Madeira Island, Portugal

Abstract

This research quantifies and compares the material damage caused by flooding resulting from the two most extreme rainfall events of the 21st century in two Portuguese regions, using insurance data: the Lisbon Metropolitan Area (LMA) and Madeira Island. During the 2000–2011 period, 24% of the claims and 40% of the payouts in the LMA were caused by the February 2008 event. In Madeira, the February 2010 event represented 50% of the claims and 88% of the payouts. The maximum rainfall values during the 2010 event more than doubling those recorded during the 2008 event. The steep slopes of the Madeira's drainage basins exacerbate the potential for flooding to cause damage. Peak discharges are higher and occur earlier than in the LMA's basins. Flash floods are the most important type of flooding in Madeira, unlike what occurs in the LMA, where urban flooding is most prevailent. The greater destructive capacity of flash floods, the higher magnitude of the triggering rainfall during the 2010 event and the higher flooding susceptibility of the Madeira's drainage basins justify the greatest material damage. The lower education levels and economic power of the Madeira's population may affect the capacity to purchase insurance and can explain the lower number of insurance policies, contributing for a higher vulnerability to flooding. The obtained results represent an important knowledge regarding flooding in Portugal for spatial planning, risk management and insurance companies.