Ensemble prediction of floods – catchment non-linearity and forecast probabilities
Quantifying the uncertainty of flood forecasts by ensemble methods is becoming increasingly important for operational purposes. The aim of this paper is to examine how the ensemble distribution of precipitation forecasts propagates in the catchment system, and to interpret the flood forecast probabi...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2007-07-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | http://www.nat-hazards-earth-syst-sci.net/7/431/2007/nhess-7-431-2007.pdf |
| _version_ | 1818645574894747648 |
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| author | C. Reszler G. Blöschl T. Haiden J. Komma |
| author_facet | C. Reszler G. Blöschl T. Haiden J. Komma |
| author_sort | C. Reszler |
| collection | DOAJ |
| description | Quantifying the uncertainty of flood forecasts by ensemble methods is becoming increasingly important for operational purposes. The aim of this paper is to examine how the ensemble distribution of precipitation forecasts propagates in the catchment system, and to interpret the flood forecast probabilities relative to the forecast errors. We use the 622 km<sup>2</sup> Kamp catchment in Austria as an example where a comprehensive data set, including a 500 yr and a 1000 yr flood, is available. A spatially-distributed continuous rainfall-runoff model is used along with ensemble and deterministic precipitation forecasts that combine rain gauge data, radar data and the forecast fields of the ALADIN and ECMWF numerical weather prediction models. The analyses indicate that, for long lead times, the variability of the precipitation ensemble is amplified as it propagates through the catchment system as a result of non-linear catchment response. In contrast, for lead times shorter than the catchment lag time (e.g. 12 h and less), the variability of the precipitation ensemble is decreased as the forecasts are mainly controlled by observed upstream runoff and observed precipitation. Assuming that all ensemble members are equally likely, the statistical analyses for five flood events at the Kamp showed that the ensemble spread of the flood forecasts is always narrower than the distribution of the forecast errors. This is because the ensemble forecasts focus on the uncertainty in forecast precipitation as the dominant source of uncertainty, and other sources of uncertainty are not accounted for. However, a number of analyses, including Relative Operating Characteristic diagrams, indicate that the ensemble spread is a useful indicator to assess potential forecast errors for lead times larger than 12 h. |
| first_indexed | 2024-12-17T00:32:55Z |
| format | Article |
| id | doaj.art-1871dcf8c5374ce6848dea0aabf93f88 |
| institution | Directory Open Access Journal |
| issn | 1561-8633 1684-9981 |
| language | English |
| last_indexed | 2024-12-17T00:32:55Z |
| publishDate | 2007-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Natural Hazards and Earth System Sciences |
| spelling | doaj.art-1871dcf8c5374ce6848dea0aabf93f882022-12-21T22:10:14ZengCopernicus PublicationsNatural Hazards and Earth System Sciences1561-86331684-99812007-07-0174431444Ensemble prediction of floods – catchment non-linearity and forecast probabilitiesC. ReszlerG. BlöschlT. HaidenJ. KommaQuantifying the uncertainty of flood forecasts by ensemble methods is becoming increasingly important for operational purposes. The aim of this paper is to examine how the ensemble distribution of precipitation forecasts propagates in the catchment system, and to interpret the flood forecast probabilities relative to the forecast errors. We use the 622 km<sup>2</sup> Kamp catchment in Austria as an example where a comprehensive data set, including a 500 yr and a 1000 yr flood, is available. A spatially-distributed continuous rainfall-runoff model is used along with ensemble and deterministic precipitation forecasts that combine rain gauge data, radar data and the forecast fields of the ALADIN and ECMWF numerical weather prediction models. The analyses indicate that, for long lead times, the variability of the precipitation ensemble is amplified as it propagates through the catchment system as a result of non-linear catchment response. In contrast, for lead times shorter than the catchment lag time (e.g. 12 h and less), the variability of the precipitation ensemble is decreased as the forecasts are mainly controlled by observed upstream runoff and observed precipitation. Assuming that all ensemble members are equally likely, the statistical analyses for five flood events at the Kamp showed that the ensemble spread of the flood forecasts is always narrower than the distribution of the forecast errors. This is because the ensemble forecasts focus on the uncertainty in forecast precipitation as the dominant source of uncertainty, and other sources of uncertainty are not accounted for. However, a number of analyses, including Relative Operating Characteristic diagrams, indicate that the ensemble spread is a useful indicator to assess potential forecast errors for lead times larger than 12 h.http://www.nat-hazards-earth-syst-sci.net/7/431/2007/nhess-7-431-2007.pdf |
| spellingShingle | C. Reszler G. Blöschl T. Haiden J. Komma Ensemble prediction of floods – catchment non-linearity and forecast probabilities Natural Hazards and Earth System Sciences |
| title | Ensemble prediction of floods – catchment non-linearity and forecast probabilities |
| title_full | Ensemble prediction of floods – catchment non-linearity and forecast probabilities |
| title_fullStr | Ensemble prediction of floods – catchment non-linearity and forecast probabilities |
| title_full_unstemmed | Ensemble prediction of floods – catchment non-linearity and forecast probabilities |
| title_short | Ensemble prediction of floods – catchment non-linearity and forecast probabilities |
| title_sort | ensemble prediction of floods ndash catchment non linearity and forecast probabilities |
| url | http://www.nat-hazards-earth-syst-sci.net/7/431/2007/nhess-7-431-2007.pdf |
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