Analyse des essais d'infiltration conduits sur le bassin de la Claduègne en Mai-Juin 2012. Contribution au WP3.4 du projet ANR FloodScale 2012-2015

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAUIn this report, we present the infiltration field campaign conducted in May-June 2015 in the 48 km2 Claduègne catchment (Ardèche, France). First we present the different measurement protocols using either simple ring infiltrometers (Beerkan method) or suction disk infiltrometers. Then the sampling strategy is presented. The theoretical aspects of infiltration equations and different methods used in infiltration tests analysis are described in details. In particular, the BEST (Beerkan Estimation of Soil Transfer) method is used in the analysis of single ring infiltration data and mini-disk infiltrometer with a -20 mm suction. This method is compared to the differential linear (DL) method, showing reasonable agreement, although systematic biases are evidenced. Multiple suction disk infiltrometers are analyzed using permanent regime equations. The single ring infiltration tests provide estimates of the retention curve and hydraulic conductivity curves. The infiltrometers provide information about the hydraulic conductivity close to saturation. We present the statistical analysis of the results, which show that the soils have generally high hydraulic conductivity, especially in forested soils. Dry bulk density is also much lower in natural soils than in cultivated soils. In situ measurements are compared with three representative pedo-transfer functions showing poor capability of the latter in reproducing observations. On the other hand, land use is found more discriminant in determining soil hydraulic properties. The statistical analysis on the samples allows defining two classes for dry bulk density with significantly different values gathering respectively natural and cultivated soils. In terms of saturated hydraulic conductivity, two land uses classes gathering forested fields and moors on the one hand, and pasture and cultivated land on the other hand can be distinguished. This allows proposing a first strategy of soil hydraulic properties spatialization in the Claduègne catchment, by combining the dry bulk density and hydraulic conductivity classes in three main families of soil hydraulic properties, depending on land use