Badland dynamics in the Central Pyrenees: temporal and spatial patterns of weathering processes

Abstract

The genesis and development of badlands is controlled by bedrock lithology, topography and climate. The development of badlands in the Central Spanish Pyrenees is favoured by the presence of marls and a climate with a marked seasonality; the combination of these factors results in active hydrosedimentological processes. The aim of the present work was to study the dynamics of badlands in the Central Pyrenees, with a focus on the temporal and spatial patterns of the dominant weathering processes. The study area was a small mountain catchment, and we focussed on the continuous observation of a number of physical parameters that control regolith development and weathering processes. Samples collected from different depths at sites with different aspects enabled temporal comparisons of the factors involved in the development of surface regolith that can be considered as indicators of the weathering of the marls. These indicators were then related to environmental variables (moisture and temperature). Atterberg limits were established and related to moisture content to explain slope dynamics and related processes. Finally, analyses of carbonate content were performed in the laboratory. The results validate the employed methodology, supporting our description of weathering processes, the established chronological sequence and the relation of these processes to climatic and topographic parameters. The results obtained since January 2004 show that the chosen indicators are sensitive to seasonal dynamics, variations in temperature and water supply, and slope aspect. The development and dynamics of regolith on north-facing slopes is more active than that on south-facing slopes. Freezethaw is the main weathering process on north-facing slopes, while south-facing slopes are dominated by the development of crusts associated with wetting-drying processes. Washing effects and lower temperatures upon north-facing slopes mean that the dissolution of carbonates is more pronounced in such areas compared with south-facing slopes, especially within the upper layers of the regolith. favoured by lithology, topography and a climate that is characterized by strong seasonal contrasts in temperature and rainfall distribution. Badlands are characterized by features such as the absence of vegetation, steep slopes and a highdensity drainage network, and hence tend to be among the most significant areas of erosion in the world. This fact is demonstrated by high concentrations of sediment in such areas, as in the Spanish Pyrenees (Valero-Garcés et al., 1999;Beguería, 2005) and the French Alps ('Terres noires'), which can exceed 1000 g l −1 (Descroix and Mathys, 2003). Badlands developed in sub-humid mountain areas are subjected to higher rates of denudation and more active dynamics compared with similar landscapes in arid or semiarid areas (Gallart et al., 2001;Regüés and Gallart, 2004). Rapid and deep weathering (Schumm, 1956), together with intense soil erosion, explain the occurrence of very high erosion rates in badland areas; in some cases...

Regional scale modeling of hillslope sediment delivery: A case study in the Barasona Reservoir watershed (Spain) using WATEM/SEDEM

“…These studies have shown that badland systems developed on Eocene marls constitute the main sediment sources in the Central Pyrenees, with important consequences for siltation of reservoirs (Valero-Garcés et al, 1999). In the Spanish Pyrenees a combination of favorable relief and climatic conditions is coupled with highly erodible marl outcrops, explaining the presence of badland systems with intense soil erosion processes (Regüés et al, 1995;Gallart et al, 2002;Nadal-Romero et al, 2007Alatorre and Beguería, 2009). (Table 6).…”

UAS photogrammetry and object-based image analysis (GEOBIA): erosion monitoring at the Kazár badland, Hungary

“…The geomorphological term 'badland' belongs to unique uncovered and shredded landscapes with steep slopes and high erosion rates being inappropriate for any kind of agricultural use (Nadal-Romero et al 2007;Caraballo-Arias et al 2015;Pintér et al 2015). Geological and mainly the lithological factors have the main influence on the evolution of these landforms (FarabegoliAgostini 2000;Neugirg et al 2016) since the occurrence of badlands is significant on soft materials (Caraballo-Arias et al 2015).…”

Daily precipitation intensity projected for the 21st century: seasonal changes over the Pyrenees

“…In contrast, few studies focus on potential shifts in the statistical distribution of daily precipitation series (e.g., Durman et al 2001;Christensen 2003, 2004;Frei et al 2003Frei et al , 2006Ekström et al 2005;Boroneant et al 2006;Beniston 2006;Beniston et al 2007). Daily precipitation is closely related to the frequency, magnitude, and duration of droughts and the occurrence of floods and associated geomorphic processes such as erosion and the initiation of landslides (Easterling et al 2000;Nadal-Romero et al 2007). Moreover, changes in the probability distribution of daily rainfall have an effect on runoff generation (MartinVide 2004), potentially either reinforcing or counteracting the impact of climate change on the availability of water resources.…”