RATU - Heavy rains and floods in urban areas | Umweltbundesamt

Background and Goals

Intensive precipitation and the natural phenomena typically associated with this, such as hail, lightning and strong, stormy winds, have various impacts on the environment, society and the life of people in Finland. A particularly illustrative example of these negative impacts were the events in the summer of 2004.  Because precipitation can vary significantly over time and by area, there is a strong probability that the full range of its variability and extremes cannot be detected by a network of pluviometers or automatic stationary measuring instruments.

This project virtually combines continuous measurements from weather radar in the summers of 2003-2004 with longer-term pluviometer measurements, in order to provide an overview of the climatological properties of the current heavy precipitation in Finland. Based on these results, new precipitation probabilities will be published. A set of regional climate model simulations will be used to calculate the future probability of heavy precipitation. The suitability of various urban hydrology models will be verified under Finish conditions. Drainage, rain drainage systems and the public drainage network will be modelled in two pilot areas. The new, radar-based precipitation probability distributions and climate change scenarios for heavy precipitation will be tested in the pilot areas, in order to investigate the level of water flows and how to deal with them.

Objectives:

• Use of weather radar to determine the intensity and frequency of heavy precipitation in Finland for periods of 15 minutes to 6 hours, within geographical areas of 1km2 to 1000  km2.
• Estimation of the climatological representativeness of weather radar data
• Estimation of the impacts of climate change on the intensity of heavy rainfall
• Determination of appropriate urban hydrology models and estimation of their applicability to Finland A test area will be modelled and simulated using the data from the exceptionally heavy rainfall in 2004.
• New optimised and modernised planning guidelines will be presented.

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