How does initial soil moisture influence the hydrological response? A case study from southern France

• Published in: Hydrology and earth system sciences 2018-11, Vol.22 (12), p.6127-6146
• Main Authors: Uber, Magdalena, Vandervaere, Jean-Pierre, Zin, Isabella, Braud, Isabelle, Heistermann, Maik, Legoût, Cédric, Molinié, Gilles, Nord, Guillaume
• Format: Article
• Language: English
• Subjects: Analysis; Atmospheric precipitations; Case studies; Catchment area; Catchment scale; Catchments; Digital filters; Electronic filters; Environmental aspects; Environmental Sciences; Flash flooding; Flash floods; Floods; Fluid filters; Graphical methods; Heavy rainfall; Hydrologic data; Hydrology; In situ measurement; Mathematical analysis; Precipitation; Precipitation (Meteorology); Precipitation data; Rain; Rainfall; Runoff; Runoff coefficient; Soil; Soil conditions; Soil moisture; Standard error; Tracers; Tracers (Biology); Variability
• ISSN: 1607-7938; 1027-5606; 1607-7938
• DOI: 10.5194/hess-22-6127-2018

The Cévennes-Vivarais region in southern France is prone to heavy rainfall that can lead to flash floods which are one of the most hazardous natural risks in Europe. The results of numerous studies show that besides rainfall and physical catchment characteristics the catchment's initial soil moisture also impacts the hydrological response to rain events. The aim of this paper is to analyze the relationship between catchment mean initial soil moisture θ̃ini and the hydrological response that is quantified using the event-based runoff coefficient ϕ.sub.ev in the two nested catchments of the Gazel (3.4 km.sup.2) and the Claduègne (43 km.sup.2). Thus, the objectives are twofold: (1) obtaining meaningful estimates of soil moisture at catchment scale from a dense network of in situ measurements and (2) using this estimate of θ̃ini to analyze its relation with ϕ.sub.ev calculated for many runoff events. A sampling setup including 45 permanently installed frequency domain reflectancy probes that continuously measure soil moisture at three depths is applied. Additionally, on-alert surface measurements at ≈10 locations in each one of 11 plots are conducted. Thus, catchment mean soil moisture can be confidently assessed with a standard error of the mean of ≤1.7 vol % over a wide range of soil moisture conditions.