title: Structured Coupling of Probability Loss Distributions: Assessing Joint Flood Risk in Multiple River Basins.
abstract: Losses due to natural hazard events can be extraordinarily high and difficult to cope with. Therefore, there is considerable interest to estimate the potential impact of current and future extreme events at all scales in as much detail as possible. As hazards typically spread over wider areas, risk assessment must take into account interrelations between regions. Neglecting such interdependencies can lead to a severe underestimation of potential losses, especially for extreme events. This underestimation of extreme risk can lead to the failure of riskmanagement strategies when they are most needed, namely, in times of unprecedented events. In this article, we suggest a methodology to incorporate such interdependencies in risk via the use of copulas. We demonstrate that by coupling losses, dependencies can be incorporated in risk analysis, avoiding the underestimation of risk. Based on maximum discharge data of river basins and stream networks, we present and discuss different ways to couple loss distributions of basins while explicitly incorporating tail dependencies. We distinguish between coupling methods that require river structure data for the analysis and those that do not. For the later approach we propose a minimax algorithm to choose coupled basin pairs so that the underestimation of risk is avoided and the use of river structure data is not needed. The proposed methodology is especially useful for large-scale analysis and we motivate and apply our method using the case of Romania. The approach can be easily extended to other countries and natural hazards.
authors.affiliation: International Institute for Applied Systems Analysis, RPV; A-2361 Laxenburg, Schlossplatz, 1, Austria.
authors.forename: Anna
authors.initials: A
authors.lastname: Timonina
authors.affiliation: International Institute for Applied Systems Analysis, RPV; A-2361 Laxenburg, Schlossplatz, 1, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hochrainer-Stigler
authors.affiliation: International Institute for Applied Systems Analysis, RPV; A-2361 Laxenburg, Schlossplatz, 1, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Pflug
authors.affiliation: Institute for Environmental Studies, VU University Amsterdam, De Boelelaan 1087, 1081HV, Amsterdam, The Netherlands.
authors.forename: Brenden
authors.initials: B
authors.lastname: Jongman
authors.affiliation: CSIRO, Land and Water, Private Bag Nr 5, POWembley, Perth, Western Australia, 6913, Australia.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Rojas
mesh_terms: D000465:Algorithms; D055868:Floods; D008962:Models, Theoretical; D011336:Probability; D045483:Rivers
keywords: Floods; Romania; hierarchical and ordered copulas; interdependencies between losses; vine copulas