Abstract
One of the effects of climate change is an increasing frequency of heavy rainfall events, which in turn leads to increased flooding damage in urban areas. The purpose of this study was to develop a tool for dynamic risk evaluation that can be used to fulfil several of the goals in the European Flood Risk Management Directive. Flood risk analysis was performed as a spatial GIS analysis with the FME software. The primary data source for the analysis was a 1D/2D model calculation, wherein 1D models described the pipeline network and the watercourses and a 2D model described surface runoff. An ArcGIS online platform was developed to visualize the results in a format understandable for decision makers. The method and tool were tested for the Norwegian capital of Oslo. The tool developed in the study enabled the efficient analysis of consequences for various precipitation scenarios. Results could be used to identify the areas most vulnerable to flooding and prioritize areas in which measures need to be implemented. The study showed that for urban areas in steep terrain, it is essential to include water velocity and depth-integrated velocity in risk analysis in addition to water depths and pipe network capacity.
Highlights
Flood is defined as “the temporary covering by water of land not normally covered by water” in the European Flood Risk Management Directive (Flood Directive) [1] (p. 3).Many cities worldwide have reported increasing damage from floods [2,3,4,5,6,7,8], including urban flooding; “urban flooding is the accumulation of floodwaters that result when the inflow of storm water exceeds the capacity of a drainage system to infiltrate water into the soil or to carry it away” [9] (p. 9)
There are many other factors in a city affecting runoff: (a) it increasingly rains more than drainage systems are designed for, and the capacity of drainage systems has deteriorated over time; (b) natural runoff routes are blocked by infrastructure; and (c) large parts of urban areas have become impermeable
The method allowed the classification of discharge risk from combined sewer system overflows (CSOs) and combined sewer system (CS) manholes based on model simulations (Figure 5)
Summary
Flood is defined as “the temporary covering by water of land not normally covered by water” in the European Flood Risk Management Directive (Flood Directive) [1] (p. 3).Many cities worldwide have reported increasing damage from floods [2,3,4,5,6,7,8], including urban flooding; “urban flooding is the accumulation of floodwaters that result when the inflow of storm water exceeds the capacity of a drainage system to infiltrate water into the soil or to carry it away” [9] (p. 9). Urban flooding can occur from several sources depending on the location of the urban environment: pluvial floods, fluvial floods, storm surges, or high tides in coastal areas. More intensive and frequent extreme rainfall events with associated floods have been projected for Europe with medium to high confidence [10]. There is high confidence that the combination of sea-level rise, storm surges in coastal cities, and extreme rainfall/river flow events will make flooding more probable. The climate is getting wetter in several parts of the world, climate change alone does not always increase flooding damage. There are many other factors in a city affecting runoff: (a) it increasingly rains more than drainage systems are designed for, and the capacity of drainage systems has deteriorated over time; (b) natural runoff routes are blocked by infrastructure; and (c) large parts of urban areas have become impermeable
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