Local urban risk assessment of dry and hot hazards for planning mitigation measures

Abstract With the change of global climate and increased urbanisation, urban dry and hot hazards is becoming a more urgent problem that may affect sustainable city development. In the case of pronounced increase of air temperature and duration of dry periods, cities may experience long-lasting heat waves, soil dryness, and water shortages that concern the urban population, ecosystems, and socio-economic sectors. The research investigates urban vulnerability towards compound dry and hot hazards in one of the largest Polish cities - Wroclaw. The aim of the paper was the development of multi-hazard framework to establish a set of metrics for a hot and dry hazards monitoring system that would provide insights into better management and sustainable development of the city in the long run. The developed indicators and thresholds system for hazard assessment covers meteorological and hydrological drought indices, heat waves, long lasting dry spells, extremely hot days, cooling degree days and low flows identification procedures. Analysis of long-term variability of the indicators values including frequency and trend analysis were the basis for the estimation of hazard levels. The main socio-economic sectors were examined in terms of their vulnerabilities to dry and hot hazards with regard to the spatial variation of sensitive city components. A combination of the estimated hazard levels and the vulnerability of the respective city sectors supported with expert judgments provided a local multi-risks urban assessment matrix. Reducing risks of dry and hot hazards requires coherent actions including educational, organisational, and technical solutions.