Integrative assessment of Badland erosion dynamics in the Oltrepo area

The present work is the result of three years of investigations on soil erosion forms and features in the Oltrepo Pavese, Northern Apennines, Italy. The aim of the work is to review from a modern and scientific point of view the badlands which crop out in the study area as well as to improve methodologies to study the sediment dynamics in badland areas. Badlands are the result of a complex interaction between sub-surface and surface runoff soil erosion processes and are a hotspot for biodiversity and geodiversity. In addition, badlands have always been a fundamental environment for soil erosion investigations. This work is based on the following four principal steps: i) the geological and structural characterisation of the study area, ii) the description of badland forms and features, iii) a probabilistic approach to determine soil erosion susceptible areas in the Oltrepo Pavese and iv) the assessment of suspended sediment dynamics at catchment scale. This study highlights a complex geological and structural sector of the Northern Apennines characterised by soft sedimentary bedrock materials that are prone to be eroded by running water. Initially, a litho-structural map was assembled, and the geological formations of the study area were grouped according to their lithology. The map represents a homogeneous base of information to classify from lithological point of view the badlands of the study area and will become a raster-base for spatial multilayer analysis. Subsequently, a geological, geomorphological and morphometrical classification of the badlands which crop out in the study area was performed though field survey and detailed terrain analysis based on Digital Terrain Models (DTM). The Oltrepo Pavese badlands were classified in type A and B according to their morphology and vegetation conditions. The badlands show high heterogeneity and can be closely related with melange bedrock, claystone and interstratified rocks. Furthermore, the badlands show the typical characteristics of Apennine badlands even if certain morphological differences were noted. This study also highlights the importance of the rainfall characteristics and land use changes playing an important role in the development and stabilisation of the badland forms and features. The land use change induced by planting operations (afforestation) and the reduction of agricultural activities in the area, as well as the reduction of the precipitation amount leads to a shrinking of badlands. Though a detailed terrain analysis and the application of the Maximum Entropy model (MaxEnt) three susceptibility maps were generated for the badland and rill-interrill erosion forms. The predictor analysis has highlighted that the more important predictors (i.e. lithology, land use, elevation) can significantly explain the diversity between calanchi type A and B. However, less significant predictors e.g. Vertical Distance to Channel Network, Valley Depth and Catchment Area are fundamental to understand the development of the two morphotypes. Finally, the study reveals for the first time, the dynamics between precipitation, discharge and suspended sediment transport in a small watershed basin sited in the Northern Apennines. A laser diffraction instrument was installed at the outlet of a small watershed basin deeply interested by aquatic erosion and the sediment diameter and concentration was evaluated with respect to rainfall. The initial moisture condition, hydrophobicity, vegetation cover, and physical conditions of the basin play a fundamental role in the assessment of sediment dynamics. Finally, the study reveals the importance of a correct land management to reduce badland erosion in the Apennine region.The present work is the result of three years of investigations on soil erosion forms and features in the Oltrepo Pavese, Northern Apennines, Italy. The aim of the work is to review from a modern and scientific point of view the badlands which crop out in the study area as well as to improve methodologies to study the sediment dynamics in badland areas. Badlands are the result of a complex interaction between sub-surface and surface runoff soil erosion processes and are a hotspot for biodiversity and geodiversity. In addition, badlands have always been a fundamental environment for soil erosion investigations. This work is based on the following four principal steps: i) the geological and structural characterisation of the study area, ii) the description of badland forms and features, iii) a probabilistic approach to determine soil erosion susceptible areas in the Oltrepo Pavese and iv) the assessment of suspended sediment dynamics at catchment scale. This study highlights a complex geological and structural sector of the Northern Apennines characterised by soft sedimentary bedrock materials that are prone to be eroded by running water. Initially, a litho-structural map was assembled, and the geological formations of the study area were grouped according to their lithology. The map represents a homogeneous base of information to classify from lithological point of view the badlands of the study area and will become a raster-base for spatial multilayer analysis. Subsequently, a geological, geomorphological and morphometrical classification of the badlands which crop out in the study area was performed though field survey and detailed terrain analysis based on Digital Terrain Models (DTM). The Oltrepo Pavese badlands were classified in type A and B according to their morphology and vegetation conditions. The badlands show high heterogeneity and can be closely related with melange bedrock, claystone and interstratified rocks. Furthermore, the badlands show the typical characteristics of Apennine badlands even if certain morphological differences were noted. This study also highlights the importance of the rainfall characteristics and land use changes playing an important role in the development and stabilisation of the badland forms and features. The land use change induced by planting operations (afforestation) and the reduction of agricultural activities in the area, as well as the reduction of the precipitation amount leads to a shrinking of badlands. Though a detailed terrain analysis and the application of the Maximum Entropy model (MaxEnt) three susceptibility maps were generated for the badland and rill-interrill erosion forms. The predictor analysis has highlighted that the more important predictors (i.e. lithology, land use, elevation) can significantly explain the diversity between calanchi type A and B. However, less significant predictors e.g. Vertical Distance to Channel Network, Valley Depth and Catchment Area are fundamental to understand the development of the two morphotypes. Finally, the study reveals for the first time, the dynamics between precipitation, discharge and suspended sediment transport in a small watershed basin sited in the Northern Apennines. A laser diffraction instrument was installed at the outlet of a small watershed basin deeply interested by aquatic erosion and the sediment diameter and concentration was evaluated with respect to rainfall. The initial moisture condition, hydrophobicity, vegetation cover, and physical conditions of the basin play a fundamental role in the assessment of sediment dynamics. Finally, the study reveals the importance of a correct land management to reduce badland erosion in the Apennine region

Bibliometric Analysis of Soil and Landscape Stability, Sensitivity and Resistivity

In times of global change, it is of fundamental importance to understand the sensitivity, stability and resistivity of a landscape or ecosystem to human disturbance. Landscapes and ecosystems have internal thresholds, giving them the ability to resist such disturbance. When these thresholds are quantified, the development of countermeasures can help prevent irreversible changes and support adaptations to the negative effects of global change. The main objective of this analysis is to address the lack of recent studies defining terms like sensitivity, resistivity and stability in reference to landscapes and ecosystems through a Bibliometric analysis based on Scopus and Web of Science peer-reviewed articles. The present research also aims to quantify landscape statuses in terms of their sensitivity, stability and resistivity. The term “landscape stability” is mainly related to quantitatively measurable properties indicating a certain degree of stability. In contrast, the term “landscape sensitivity” is often related to resilience; however, this definition has not substantially changed over time. Even though a large number of quantification methods related to soil and landscape stability and sensitivity were found, these methods are rather ad hoc. This study stresses the importance of interdisciplinary studies and work groups

A methodology to detect and characterize uplift phenomena in urban areas using Sentinel-1 data

This paper presents a methodology to exploit the Persistent Scatterer Interferometry (PSI) time series acquired by Sentinel-1 sensors for the detection and characterization of uplift phenomena in urban areas. The methodology has been applied to the Tower Hamlets Council area of London (United Kingdom) using Sentinel-1 data covering the period 2015–2017. The test area is a representative high-urbanized site affected by geohazards due to natural processes such as compaction of recent deposits, and also anthropogenic causes due to groundwater management and engineering works. The methodology has allowed the detection and characterization of a 5 km2 area recording average uplift rates of 7 mm/year and a maximum rate of 18 mm/year in the period May 2015–March 2017. Furthermore, the analysis of the Sentinel-1 time series highlights that starting from August 2016 uplift rates began to decrease. A comparison between the uplift rates and urban developments as well as geological, geotechnical, and hydrogeological factors suggests that the ground displacements occur in a particular geological context and are mainly attributed to the swelling of clayey soils. The detected uplift could be attributed to a transient effect of the groundwater rebound after completion of dewatering works for the recent underground constructions

What makes soil landscape robust? Landscape sensitivity towards land use changes in a Swiss southern Alpine valley

Landscape sensitivity is a concept referring to the likelihood that changes in land use may affect in an irreversible way physical and chemical soil properties of the concerned landscape. The objective of this study is to quantitatively assess the sensitivity of the southern Alpine soil landscape regarding land use change-induced perturbations. Alpine soil landscapes can be considered as particularly sensitive to land use changes because their effects tend to be enhanced by frequent extreme climatic and topographic conditions as well as intense geomorphologic activity. In detail, the following soil key properties for soil vulnerability were analysed: (i) soil texture, (ii) bulk density, (iii) soil organic carbon (SOC), (iv) saturated hydraulic conductivity (Ksat), (v) aggregate stability and (vi) soil water repellency (SWR). The study area is characterized by a steep, east-west oriented valley, strongly anthropized in the last centuries followed by a progressive abandonment. This area is particularly suitable due to constant lithological conditions, extreme topographic and climatic conditions as well as historic land use changes. The analysis of land use change effects on soil properties were performed through a linear mixed model approach due to the nested structure of the data. Our results show a generally high stability of the assessed soils in terms of aggregate stability and noteworthy thick soils. The former is remarkable, since aggregate stability, which is commonly used for detecting land use-induced changes in soil erosion susceptibility, was always comparably high irrespective of land use. The stability of the soils is mainly related to a high amount of soil organic matter favouring the formation of stable soil aggregates, decreasing soil erodibility and hence, reducing soil loss by erosion. However, the most sensitive soil property to land use change was SWR that is partly influenced by the amount of soil organic carbon and probably by the quality and composition of SOM

Geomorphology of the upper Mkhomazi River basin, KwaZulu-Natal, South Africa, with emphasis on late Pleistocene colluvial deposits

We present a 1:50 000 scale geomorphological map of the upper Mkhomazi River basin, located in the foothills of the Drakensberg mountains in KwaZulu-Natal Province, South Africa. The sub-horizontal strata of the Permo-Triassic Beaufort Group forms plateau interfluves with a concave valley slope morphology. Locally, thick sequences of late Pleistocene colluvial deposits and associated buried paleosols (Masotcheni Formation) infill first-order tributary stream valleys and extend across the adjacent lower slopes. Surface runoff processes preferentially incise into the poorly consolidated, highly erodible sediments causing severe gully erosion that is responsible for widespread land degradation and desertification phenomena. The main purpose of this work is to derive a geomorphological map of the study area focussing on the erosional landforms to understand their spatial distribution and their relation to the colluvial deposits. Finally, a local and regional stratigraphic correlation of colluvial deposits and associated buried palaeosol profiles is proposed

Geomorphological processes, forms and features in the surroundings of the Melka Kunture Palaeolithic site, Ethiopia

The landscape of the surroundings of the Melka Kunture prehistoric site, Upper Awash Basin, Ethiopia, were studied intensively in the last decades. Nonetheless, the area was mainly characterized under a stratigraphic/geological and archaeological point of view. However, a detailed geomorphological map is still lacking. Hence, in this study, we identify, map and visualize geomorphological forms and processes. The morphology of the forms, as well as the related processes, were remotely sensed with available high-resolution airborne and satellite sources and calibrated and validated through extensive field work conducted in 2013 and 2014. Furthermore, we integrated multispectral satellite imagery to classify areas affected by intensive erosion processes and/or anthropic activities. The Main Map at 1:15,000 scale reveals structural landforms as well as intensive water-related degradation processes in the Upper Awash Basin. Moreover, the map is available as an interactive WebGIS application providing further information and detail (www.roceeh.net/ethiopia_ geomorphological_map/)

Bibliometric Analysis of Soil and Landscape Stability, Sensitivity and Resistivity

In times of global change, it is of fundamental importance to understand the sensitivity, stability and resistivity of a landscape or ecosystem to human disturbance. Landscapes and ecosystems have internal thresholds, giving them the ability to resist such disturbance. When these thresholds are quantified, the development of countermeasures can help prevent irreversible changes and support adaptations to the negative effects of global change. The main objective of this analysis is to address the lack of recent studies defining terms like sensitivity, resistivity and stability in reference to landscapes and ecosystems through a Bibliometric analysis based on Scopus and Web of Science peer-reviewed articles. The present research also aims to quantify landscape statuses in terms of their sensitivity, stability and resistivity. The term “landscape stability” is mainly related to quantitatively measurable properties indicating a certain degree of stability. In contrast, the term “landscape sensitivity” is often related to resilience; however, this definition has not substantially changed over time. Even though a large number of quantification methods related to soil and landscape stability and sensitivity were found, these methods are rather ad hoc. This study stresses the importance of interdisciplinary studies and work groups

Land use effects on surface runoff and soil erosion in a southern Alpine valley

In mountain regions, soil landscapes are highly vulnerable against soil loss. Moreover, these environments are particularly affected by land use changes, which influence soil properties and related processes like surface runoff generation and soil erosion. These processes are in turn amplified by extreme climatic events and intensive geomorphological dynamics. The objective of this study is to quantitatively assess the effects of land use changes on surface runoff and soil erosion in a southern Alpine valley (Onsernone valley, Switzerland) characterized by a former intense land use followed by a progressive abandonment in the last decades. Surface runoff and related sediment transport has been analysed under controlled and reproducible conditions using a portable rainfall simulator device (1 m2). The results show a statistically significant increase in surface runoff when the soil gets water repellent reducing the surface infiltration capacity and generating preferential flow paths, which prevent a homogeneous wetting of the soil. However, the documented high sensitivity of surface runoff to land use changes does not result in an equally high sensitivity to soil erosion processes. Instead, soils display a high aggregate stability leading to very low sediment transports except for abandoned and reforested agricultural terraces. There, the lack of maintenance and progressive collapse of terrace dry walls locally increase slope angles and directly exposes the soil to atmospheric agents and surface runoff, which causes soil erosion rates beyond the customary natural level