Abstract
In times of increasing weather extremes and expanding vulnerable cities, a significant risk to civilian security is posed by heavy rainfall induced flash floods. In contrast to river floods, pluvial flash floods can occur anytime, anywhere and vary enormously due to both terrain and climate factors. Current early warning systems (EWS) are based largely on measuring rainfall intensity or monitoring water levels, whereby the real danger due to urban torrential floods is just as insufficiently considered as the vulnerability of the physical infrastructure. For this reason, this article presents a concept for a risk-based EWS as one integral component of a multi-functional pluvial flood information system (MPFIS). Taking both the pluvial flood hazard as well as the damage potential into account, the EWS identifies the urban areas particularly affected by a forecasted heavy rainfall event and issues object-precise warnings in real-time. Further, the MPFIS performs a georeferenced documentation of occurred events as well as a systematic risk analysis, which at the same time forms the foundation of the proposed EWS. Based on a case study in the German city of Aachen and the event of 29 May 2018, the operation principle of the integrated information system is illustrated.
Highlights
Flash floods are natural hazards that are defined as fast surface flows with high peak discharge values, often limited in their spatial extent [1]
Pluvial flooding occurs when rainfall with a high intensity exceeds the infiltration capacity of soil, or the discharge capacity of sewage and drainage systems, and water flows uncontrolled through urban areas [5]
According to the World Meteorological Organization (WMO), flash floods are among the natural hazards with the highest mortality rate and cause devastating property damage every year [7]
Summary
Flash floods are natural hazards that are defined as fast surface flows with high peak discharge values, often limited in their spatial extent [1]. The most frequent cause of this type of flood is heavy rainfall events [2], the expression pluvial flash flood is used [3,4]. According to the World Meteorological Organization (WMO), flash floods are among the natural hazards with the highest mortality rate (deaths/people affected) and cause devastating property damage every year [7]. Due to the physical characteristics of convective heavy rainfall cells, the forecasting time of pluvial flash floods is, unlike river (fluvial) floods, very short [8]
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