Jamshid Farifteh

Factors underlying piping in the Basilicata region, southern Italy

Abstract Piping/tunnelling erosion is a widely spread process in the Plio-Pleistocene marine clays of the Basilicata region in southern Italy. The pipes are often closely concentrated along the surface drainage networks at different depths with a tunnel (length) and a diameter varying from just a few centimetres to some metres. The formation and evolution of pipes in the badlands can be explained through: (1) geo-structural characteristics of the clay, (2) material properties such as a high exchangeable sodium percentage, (3) favourable climatic conditions, and (4) hydraulic gradient along the path controlled by the gully or ravine bottom that is acting as a local drain. The exposure and the extension of joints at the surface and in the bedrock along the slope are the main factors required for development of the pipes. The absence of the piping erosion on the slopes, where a reasonably thick layer of the soil material covers the open joints, shows that although certain material properties and climatic conditions play an important role, they are not sufficient to develop extensive piping erosion in the area.

Similarity measures for spectral discrimination of salt-affected soils

This paper illustrates a pilot study designed to examine the spectral response of soils due to salt variations. The aim of the study includes determining whether salt‐affected soils can be discriminated based on their spectral characteristics, by establishing a relationship between soil properties and soil spectra and by testing if variations in the spectra of salt‐affected soil samples are statistically significant. To answer the research questions, a laboratory experiment was designed to simulate salt transport to a column of soil in order to provide direct measurements of soil spectra and soil properties when salt concentration in a soil sample changes. The measured spectra were examined by the application of spectral matching techniques to quantify the variations and ascertain a relationship that supports the spectral identification of saline soils. The Wards grouping method was conducted as an exploratory tool to statistically create homogeneous classes among data, which were obtained from the application of the spectral matching techniques to salt affected soil spectra. A nonparametric statistical test (Mann–Whitney U‐test) was used to determine whether the differences between the classes are statistically significant. The results of spectral matching techniques showed differences in absorption strength, absolute reflectance and spectral angle in the near and shortwave infrared regions. The results also showed significant correlations between soil electrical conductivity (EC) and spectral similarity measures, indicating that similarity between the samples spectra decreases as the salt concentration in the soil increases. The generated clusters indicate two classes at the highest level, which were subdivided at the next level and further subdivided into multiple subclasses as the dissimilarity decreased. The spectral data were grouped into classes and were used to test the null hypothesis by applying the Mann–Whitney U‐test. The results indicate a significance level of α<0.02 between salinity classes and α<0.05 per waveband, meaning variations between the classes are higher than within each class.

Evaluating land degradation for assessment of land vulnerability to desert conditions in the Sokoto area, Nigeria

There are no standard indicators to evaluate or predict desertification. This paper describes an attempt to assess vulnerability to desert conditions in part of the Sokoto district in northwestern Nigeria, using remote sensing coupled with other ancillary data (erosion, sealing, crusting, compaction, cover change, organic matter monitoring, salinity and aridification) within a geographic information system environment.