‘risk-calculator’: a tool for multi-hazard risk assessments

Effects of a hazard can be expressed in terms of the losses and damages caused by it. These risk assessments help decision makers and disaster managers to better prepare for and cope with the disasters arising from hazards in all three phases (preparation, response and recovery) of disaster risk reduction and resilience. With the growth of disaster risk globally (GAR, 2022), and also the related research on different components of risk (hazard, exposure, vulnerability), there is a rising demand to compute risk for multi-hazard events, for which an integrated tool is very beneficial, but most of the tools used for multi-hazard risk assessment purposes are not available for public use (Cees J. van Westen and Stefan Greiving, 2017).

The ‘risk-calculator’ is an open-source Python program that enables users to do multi-hazard scenario risk assessments. This program is  capable of assessing loss and damage for different sets of discrete or continuous vulnerability or fragility functions for different concurrent hazards, such as floods, earthquakes and tsunamis.

The three main inputs are: (1) hazard, expressed as an intensity field (e.g ShakeMap for earthquakes or inundation field for tsunamis and floods), (2) the exposure model provided in a geospatial database or as CSV files to be imported, and (3) vulnerability/fragility functions describing the level of loss or damage at different intensity measure levels dependent on the asset taxonomy and the hazard type. The tool works on basis of the standard taxonomy as defined by the Global Earthquake Model. This taxonomy can also be expanded to include damage states of previous events for a loss computation of cascading events such an earthquake followed by a tsunami.

Apart from using the program directly, users can connect to the API designed for this program to run loss assessments. The resulting losses and damages are provided in a geospatial database (SpatiaLite or GeoPackage), for sake of easier handling and plotting. This user-friendly program provides database views, connecting data in a meaningful way from different tables to allow for various ways of analyzing and visualizing the loss and damage assessments.