Geomorphological Characterization of Rivers Using Virtual Globes and Digital Elevation Data: A Case Study from the Naryn River in Kyrgyzstan

In recent years, fluvial geomorphology included a range of new technologies for the characterization of riverine landscapes in the pool of methods. LIDAR, the analysis of drone imagery or satellite remote sensing improved the ability to analyze river systems in manifold ways. However, the high demand for (often expensive) data and processing skills limit the application commonly to smaller study reaches or to regions where data is already available. In contrast, a range of conceptual frameworks for the geomorphological characterization of river systems highlights the relevance of integrating the catchment scale context. Against this background, virtual globes such as Google Earth are cost-efficient alternatives as they make high resolution satellite imagery available almost worldwide. Merging the information mapped from virtual globes with digital elevation data allows the interpretation of riverscape attributes in the context of the longitudinal profile. In our study, we present the geomorphological mapping of the more than 600 km long Naryn River in Kyrgyzstan based on different virtual globes and the SRTM-1 digital elevation model. The experience from this mapping exercise suggests that the combination of virtual globe imagery and elevation data is a powerful and cost-efficient approach for river research and application in the context of data-scarce river corridors.</jats:p

Soil particle size distribution and induced soil carbon transport by ephemeral gully erosion in Mediterranean mountain arable land

11 Pags.- 2 Tabls.- 8 Figs.In Mediterranean mountain agroecosystems, soil erosion associated with the development of ephemeral gullies is a common environmental problem that contributes to a loss of nutrient‐rich topsoil. Little is known about the influence of ephemeral gully erosion on particle size distribution and its effect on soil organic (SOC) and inorganic (SIC) carbon among different sized soil particles in agricultural soils. In this study, laboratory tests were conducted using velocity settling tube experiments to examine the effects of erosion on sediment particle size distributions from an incised ephemeral gully, associated with an extreme event (235 mm). We also consider subsequent deposition on an alluvial fan in order to assess the distribution of SOC and SIC concentrations and dissolved carbon before and after the extreme event. Soil fractionation was carried out on topsoil samples (5 cm) collected along an ephemeral gully in a cultivated field, located in the lower part of a Mediterranean mountain catchment. The results of this study showed that the sediment transported downstream by runoff plays a key role in the particle size distribution and transportability of soil particles and associated carbon distribution in carbonate rich soils. The eroding sediment is enriched in clay and silt‐sized particles at upslope positions with higher SOC contents and gradually becomes coarser and enriched in SIC at the end of the ephemeral gully because the finest particles are washed‐out of the study field. The extreme event was associated with an accumulation of dissolved organic carbon at the distal part of the depositional fan. Assessment of soil particle distribution using settling velocity experiments provides basic information for a better understanding of soil carbon dynamics in carbonate rich soils. Processes of soil and carbon transport and relationships between soil properties, erodibility and aggregate stability can be helpful in the development of more accurate soil erosion models.This work was funded by the CICYT project(CGL2014-52986-R).Peer reviewe

Slope instabilities in steep cultivation systems: Process classification and opportunities from remote sensing

The cultivation of steep slopes is a widespread practice in hilly and mountainous areas around the world. Such environments often result in particular agricultural systems linked with unique local values of historical and cultural heritage, economy, and food security. However, steep‐slope agriculture is inherently exposed to slope instability processes, which are now widely aggravated due to natural (e.g., growing rainfall aggressiveness) and anthropogenic factors (e.g., unsuitable maintenance or agronomic practices). In the literature, among the many articles published on soil erosion, a specific focus on the analysis of slope instabilities in steep cultivation systems is lacking. The purpose of this article is, therefore, to create a specific overview of this problem, with some useful insights into the role of remote sensing. We introduce the problem first, highlighting the main issues related to slope instabilities in steep cultivated areas. Then we provided a classification of key published papers, based on the different types of mass movements studied and their location in the world. The spatial comparison of past research and estimated global hazard of the mass movement in agricultural areas highlighted a relevant bias: a strong scientific focus on southern European countries, yet large rural areas are at risk on all continents, many of these unexplored by science. The third section is related to the contribution of remote sensing technologies (e.g., LiDAR and RPAS photogrammetry) in mapping the investigated processes. This study could help to guide future research for better management of such socio‐economically relevant agricultural landscapes