Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2018-17
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
28 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Convection-permitting regional climate simulations for representing floods in small and medium sized catchments in the Eastern Alps
Christian Reszler1, Matthew Blasie Switanek2, and Heimo Truhetz2 1JR-AquaConSol GmbH, Steyrergasse 21, 8010 Graz, Austria
2Wegener Center for Climate and Global Change, University of Graz, 8010 Graz, Austria
Abstract. Small scale floods are a consequence of high precipitation rates in small areas that can occur along frontal activity and convective storms. This situation is expected to become more severe due to a warming climate, when single precipitation events resulting from deep convection become more intense (Super Clausius-Clapeyron effect). Regional climate model (RCM) evaluations and inter-comparisons have shown that there is evidence that an increase in regional climate model resolution and in particular, at the convection permitting scale, will lead to a better representation of the spatial and temporal characteristics of heavy precipitation at small and medium scales. In this paper, the benefit of grid size reduction and bias correction in climate models are evaluated in their ability to properly represent flood generation in small and medium sized catchments. The climate models are coupled with a distributed hydrological model. The study area is the Eastern Alps, where small scale storms often occur along with heterogeneous rainfall distributions leading to a very local flash flood generation. The work is carried out in a small multi-model (ensemble) framework using two different RCMs (CCLM and WRF) in different grid sizes. Bias correction is performed by the use of the novel Scaled Distribution Mapping (SDM) method. The results show, that for small catchments (< 200 km²) a resolution of 3 km is essential to accurately simulate the magnitude of flood events. Flood frequency and seasonality are both represented well in all catchments. In the larger catchments resolutions of 12.5 km and 50 km already yield statistically satisfying results, but poor results regarding seasonality. Also, due to the short response times in the small sub-catchments a time step of 1 hour is required. In all setups a bias still exists in precipitation and temperature, which sometimes leads to unrealistic hydrological conditions demonstrating the necessity of bias correction. The results show the added value of reducing grid size and bias correction in climate models that can be used to model flood mechanisms in small and medium sized catchments.
Citation: Reszler, C., Switanek, M. B., and Truhetz, H.: Convection-permitting regional climate simulations for representing floods in small and medium sized catchments in the Eastern Alps, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2018-17, in review, 2018.
Christian Reszler et al.
Christian Reszler et al.
Christian Reszler et al.

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Short summary
Small scale floods are a consequence of high rainfall rates in small areas that can occur along frontal activity and convective storms. This situation is expected to become more severe due to a warming climate. This study shows the benefit of fine-gridded (~ 3 km spacing) climate models combined with appropriate error correction techniques for flood modelling in small and medium sized catchments. Requirements are presented to further bridge the scale gap between climatology and hydrology.
Small scale floods are a consequence of high rainfall rates in small areas that can occur along...
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