Use of regionalized stormflow coefficients with a view to hydroclimatological hazard mapping

Abstract

An attempt was made to compensate for the lack of long hydrological time series and the lack of information on maximum streamflow in the Alzette River basin (Luxembourg) via the regionalization of stormflow coefficients. Streamflow data recorded since 1995 with a very dense streamgauge network allowed the determination of maximum stormflow coefficients in 18 sub-basins of the Alzette. The stormflow coefficients were then regionalized via stepwise multiple regression analysis for 83 different sub-basins of the Alzette. Combined with 10-year daily rainfall heights (statistical estimation), this regionalization allowed the spatial variability of storm runoff in the Alzette basin to be mapped, thus providing a view of hazard and risk-producing areas, as well as of risk-exposed areas. In a basin with little historical hydrological information this technique can help identify areas where storm runoff reducing measures should be applied from the outset. Key words stormflow coefficients; regionalization; hazard mapping; Alzette hasin, Luxembourg Utilisation de coefficients d'écoulement de crue régionalisés en vue de la cartographie de l'aléa hydro-climatologique Résumé Cette étude présente une tentative de pallier le manque de longues séries d'observations hydrologiques dans le bassin de l'Alzette (Luxembourg) à l'aide d'une régionalisation de coefficients d'écoulement de crue. Les observations hydrologiques réalisées depuis 1995 dans 18 sous-bassins de l'Alzette ont permis de déterminer des coefficients d'écoulement de crue maximum (K nrdX ). Les K m3X régionalisés à l'aide d'une régression multiple par étapes ont été déterminés pour 83 sous-bassins de l'Alzette. La superposition des coefficients d'écoulement de crue régionalisés et d'une pluie journalière théorique décennale a permis d'établir une carte détaillée de la variabilité spatiale de l'écoulement de crue dans le bassin de l'Alzette. Cette carte permet de distinguer clairement les zones productrices des aléas et des risques hydrologiques des zones exposées aux risques hydrologiques. Dans un bassin où l'historique hydrologique fait défaut, cette technique permet d'identifier les zones où les mesures visant à réduire l'écoulement de crue devraient être appliquées prioritairement. Mots clefs coefficient d'écoulement de crue; régionalisation; cartographie de l'aléa; bassin de l'Alzette, Luxembourg

Rainfall–runoff response and event-based runoff coefficients in a humid area (northwest Spain)

“…5 it is clear that, as the catchment becomes wet, the hydrological response increases and, consequently, it represents a greater percentage of rainfall. Probably the antecedent soil moisture state plays an important role in the hydrological response of the catchment, as has been often suggested for temperate humid catchments (Dunne et al 1975, Pfister et al 2002, Norbiato et al 2009, Penna et al 2011. However, over the study period, the observed seasonality of the runoff coefficients was also possibly affected by rainfall characteristics, such as large and long rainfall events occurring in 2006.…”

“…It affects infiltration capacity and the capability of soils to store new rainfall water. Hence, the different runoff generating processes are highly regulated by soil characteristics and especially by soil moisture, and not by rainfall characteristics (Jordan 1994, Pfister et al 2002, Merz and Blöschl 2009.…”

Assessing winter storm flow generation by means of permeability of the lithology and dominating runoff production processes

“…basins ranging in size from 10 km 2 to 10 3 km 2 ; Blöschl, 1996) to rainfall during winter. The permeability of the substratum was found to be an important basin characteristic in describing the C-value of basins in the Grand Duchy of Luxembourg (Pfister et al, 2002) and it will serve in this study as a single independent parameter in a first model, which is based on linear regression, to describe the C-value with. Since soils form the first medium between precipitation and runoff generating processes after the vegetation cover, they will serve in this study as independent parameters for a second model.…”

“…The previously named basin characteristics served as independent parameters. The C-value is defined as the ratio between storm flow and rainfall, is supposed to be basin specific and to have a strong seasonal variability, and should be more or less constant during winter, expressing the saturated state of the basin (Pfister et al, 2002). Uhlenbrook et al (2004) pointed out that in meso-scale basins processes combine into a more complex way, producing an integrated runoff response to rainfall.…”

“…Mazvimavi (2003) listed the most commonly used physiographic basin characteristics in regression analyses, which are: land use, geology, drainage density and basin area. Pfister et al (2002) developed a methodology that determines the qualitative behavior of gauged basins with short historical data series with a view to regionalization, using the winter storm flow coefficient, or C-value, as the dependent parameter in a regression analysis. The previously named basin characteristics served as independent parameters.…”