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Gully erosion is known to affect soil productivity, and to limit land use in many parts of the world. To assess the susceptibility of soils to gully erosion, the triggering factors must be analyzed. A simulation of gully development over time was implemented in Python – GIS modules based on the topographic characteristics of the study area, soil properties, and measured runoff. The results show that the developed modules allow a successful data preparation, process simulation and spatial visualization of the obtained results in 2D and 3D as well as an analysis of time series of gully evolution. [ABSTRACT FROM AUTHOR]

Gully erosion affects the landscape and human life in many ways, including the destruction of agricultural land and infrastructures, altering the hydraulic potential of soils, as well as water availability. Due to climate change, more areas are expected to be affected by gully erosion in the future, threatening especially low-income agricultural regions. In the past decades, quantitative methods have been proposed to simulate and predict gully erosion at different scales. However, gully erosion is still underrepresented in modern GIS-based modeling and simulation approaches. Therefore, this study aims to develop a QGIS plugin using Python to assess gully erosion dynamics. We explain the preparation of the input data, the modeling procedure based on Sidorchuk's (Sidorchuk A (1999) Dynamic and static models of gully erosion. CATENA 37:401–414.) gully simulation model, and perform a detailed sensitivity analysis of model parameters. The plugin uses topographical data, soil characteristics and discharge information as gully model input. The plugin was tested on a gully network in KwaThunzi, KwaZulu-Natal, South Africa. The results and sensitivity analyses confirm Sidorchuck's earlier observations that the critical runoff velocity is a main controlling parameter in gully erosion evolution, alongside with the slope stability threshold and the soil erodibility coefficient. The implemented QGIS plugin simplifies the gully model setup, the input parameter preparation as well as the post-processing and visualization of modelling results. The results are provided in different data formats to be visualized with different 3D visualization software tools. This enables a comprehensive gully assessment and the derivation of respective coping and mitigation strategies. [ABSTRACT FROM AUTHOR]

Rockfall is a natural hazard in mountainous areas not to be underestimated. Mass activities differing in rock volume may cause considerable economic damage. Accomplishing qualitative appraisal of high-potential zones for rockfall is a first step towards implementing mitigation strategies. Nowadays, Geographical Information Systems (GIS) are the state-of-the-art tool for a fast and economic approach of identifying potential hazard zones rather than using conventional mapping with in-situ field data. Primarily, current research focuses on designing and implementing user-friendly tools delineating potential rockfall hazard zonation (RHZ). The constructed model examines triggering factors like slope, aspect, elevation, lithology, structural lineament, rainfall intensity, and seismic activity focal depth of a mountainous coastal region (Gulf of Aqaba, Egypt). The extracted geomorphological parameters were based on a high-resolution TanDEM-X Digital Elevation Model. The enhanced Landsat ETM + 7 was used to generate the lithological and structural lineament parameters, while the rainfall data were collected from NASA project tool. The zonation model was implemented by means of ESRI's ArcGIS Pro ModelBuilder. Google Earth Pro orthophotos compared with the generated rockfall hazard zonation map indicate the potential RHZ with high reliability. The achieved results show that 15 % of the study area qualifies as a high rockfall hazard zone. As the RHZs generated by the model depend on the input data and the selected rating scores and weights, obtaining ground truth is essential to get a trustworthy result. Finally, this study recommends employing the built RHZ model on similar terrains worldwide to support decision-makers involving any sustainable development projects. [ABSTRACT FROM AUTHOR]

Fractured crystalline aquifer is considered as the main source of water supply in most of the arid and semi-arid regions. Fractures play an essential role as pathways through which groundwater flows from high catchments to supply the productive wells in lowlands. The hydraulic conductivity measurements for highly fractured crystalline aquifers are a must for optimal management of groundwater extraction from these aquifers. The current work aims at estimating the hydraulic conductivity of the crystalline aquifer by using an unconventional approach based entirely on the processing of remotely-sensed lineament data and field observations. Extracted lineaments at four sites near the productive wells along Wadi Nasab area (WNA) were traced from Landsat (ETM+7) and other ancillary geological data by using image processing and GIS tools. Hence, four discrete fracture networks (DFN) were designed and practiced for the selected test sites to model the groundwater flow through the fracture system in order to estimate the hydraulic conductivity of the investigated crystalline aquifer. The achieved results indicated that the hydraulic conductivity of fractured basement aquifer of WNA varied between 2.3 × 10−7 and 6.1 × 10−7 m/s. The estimated hydraulic conductivity values are close to the values of previous field infiltration tests in the nearby area at Sinai. The previously estimated infiltration rates (expressing the vertical hydraulic conductivity) on the fractured crystalline outcrops ranged between 2.6 × 10−6 and 6.5 × 10−7 m/s, which are concordant with achieved results. Moreover, the achieved values match the previously published values of hydraulic conductivity for similar crystalline aquifers around the world, reflecting the high validity of the used unconventional, low-cost approach to estimate the hydraulic conductivity of fractured crystalline aquifers. The designed approach can be potentially practiced on similar basins in Sinai peninsula and other comparable basins having similar geological and climatic environments around the world. Research Highlights: Estimating the hydraulic conductivity of fractured crystalline aquifer by using remotely sensed lineament data and field observations. Discrete fracture networks (DFN) models the groundwater flow to estimate the hydraulic conductivity of the crystalline aquifer. The estimated hydraulic conductivity values are varied between 2.3 × 10-7 m/s and 6.1×10-7 m/s, which come in agreement with the previously estimated values using the conventional infiltration tests. The results reflect the validity of using this unconventional and low-cost approach to estimate the hydraulic conductivity of fractured crystalline aquifers. [ABSTRACT FROM AUTHOR]

Badlands are characteristic erosional forms distributed along the entire Apennines. In the Italian context badland areas are called "calanchi", the plural of the word "calanco". In this paper we present the first calanchi inventory map of the Oltrepo Pavese area, Northern Apennines (Italy). In total 263 calanchi were mapped using remote sensing techniques like Orthophotos, Google Earth images, as well as field recognition. Moreover, calanchi were characterised from a geomorphologic, geologic and a morphometric point of view. The calanchi of the Oltrepo Pavese have been categorised in two geomorphological classes based on process related morphologies. In the study area calanchi mainly occur in soft sedimentary bedrock materials such as melanges, marls, claystones, and interstratified rocks. The results show that calanchi formations are often related to faults and tectonic lineaments present in the study area. Moreover, we analyse a 5 m cell size Digital Terrain Model to detect correlations between calanchi and morphometric indices. The calanchi, defined and categorised for the first time in the study area, show typical morphometric characteristics of Apennine calanchi forms and features. In particular, they occur on concave south-facing slopes on soft bedrock formations. Finally, a multitemporal air photo interpretation over a 40 years period indicated a general decrease in calanchi areas. The area reduction is mainly correlated to intensive land use changes combined with variations of precipitation pattern. The revegetation trend was also confirmed by NDVI analysis based on Landsat satellites images. The calanchi were digitized and stored in a GIS database providing the information for future quantitative modelling assessments. • We generated a first inventory map of the Oltrepo Pavese calanchi forms and features. • Calanchi have been classified in two morphogenetic types (Type A; Type B). • Calanchi develop mainly in soft sedimentary bedrock formations. • A general trend in area reduction has been observed for the calanchi forms and features. • NDVI and land use change analysis confirm revegetation processes. [ABSTRACT FROM AUTHOR]

Damages caused by flash floods hazards are an increasing phenomenon, especially in arid and semi-arid areas. Thus, the need to evaluate these areas based on their flash flood risk using maps and hydrological models is also becoming more important. For ungauged watersheds a tentative analysis can be carried out based on the geomorphometric characteristics of the terrain. To process regions with larger watersheds, where perhaps hundreds of watersheds have to be delineated, processed and classified, the overall process need to be automated. GIS packages such as ESRI's ArcGIS offer a number of sophisticated tools that help regarding such analysis. Yet there are still gaps and pitfalls that need to be considered if the tools are combined into a geoprocessing model to automate the complete assessment workflow. These gaps include issues such as i) assigning stream order according to Strahler theory, ii) calculating the threshold value for the stream network extraction, and iii) determining the pour points for each of the nodes of the Strahler ordered stream network. In this study a complete automated workflow based on ArcGIS Model Builder using standard tools will be introduced and discussed. Some additional tools have been implemented to complete the overall workflow. These tools have been programmed using Python and Java in the context of ArcObjects. The workflow has been applied to digital data from the southwestern Sinai Peninsula, Egypt. An optimum threshold value has been selected to optimize drainage configuration by statistically comparing all of the extracted stream configuration results from DEM with the available reference data from topographic maps. The code has succeeded in estimating the correct ranking of specific stream orders in an automatic manner without additional manual steps. As a result, the code has proven to save time and efforts; hence it's considered a very useful tool for processing large catchment basins. [ABSTRACT FROM AUTHOR]

In this article we present a detailed litho-structural map of the Oltrepo Pavese, a sector of the Northern Apennines, Southern Lombardy, Italy. Lithology and geological structures are an important basis for different disciplines of Earth Sciences. In particular, for the assessment of earth surface processes such as soil erosion, mass movements, flooding, etc. The Oltrepo Pavese is characterised by a complex geology and related tectonic settings. In this study, we conducted a comprehensive lithological mapping approach considering existing geological maps, and detailed field surveys. The lithotypes have been subdivided into 11 classes based on the dominant outcropping lithologies. Integrating bibliographic data and a detailed Digital Terrain Analysis of a high-resolution DTM (5 m) we detected faults, folds and tectonic lineaments in the study area. The final result is represented by a litho-structural map of the Oltrepo Pavese-area, consisting in two shape files elaborated in an open source GIS environment. [ABSTRACT FROM AUTHOR]

• Sediment dynamics of a small watershed in the Northern Apennines was assessed. • The watershed is affected by rill-interrill and calanchi erosion. • A morphometrical characterisation of the basin was performed using a DEM. • A suspended sediments were assessed using a laser diffraction technique. • SSC and SMD were related to the available rainfall data. The volumes and dynamics of suspended sediments drained from a watershed are often unknown, especially in small creeks and tributaries where continuous discharge measurements are seldom available. The objective of this study was to assess in a qualitative and quantitative way the sediment dynamics of a small ungauged watershed in the Northern Apennines, Italy. We analysed and correlated the sediment volume concentration and grain-size distribution of the suspended sediments with the precipitation pattern. The study area is a small ungauged watershed (0.15 km2) that is dominated by intensive soil erosion processes and related landforms. The basin is oriented East-West with the south-facing slopes characterized by badland erosion processes. The north-facing slopes are cultivated and dominated by rill-interrill erosion phenomena. An morphometrical characterization of the basin was performed using a high-resolution DTM with a 1 × 1 m resolution. Subsequently, the physical characteristics of the topsoil were investigated based on grain size laboratory analysis. A detailed NDVI analysis of the vegetation was performed using Sentinel-2A images. Finally, we assessed the suspended sediments at the outlet of the basin using a laser diffraction technique. The Suspended Sediment Volume Concentration (SSC) and the Sauter Mean Diameter (SMD) of the eroded sediments, provide insights into the morphogenetic processes and the sediment transport dynamics of the basin. The measurements were conducted in autumn 2018 after an intense precipitation period and in spring 2019 after a dry phase. The results show a direct relationship between precipitation and SSC with a delay of about 2 h after the most intense precipitation events. Moreover, we reveal that the SMD values are inversely related to the precipitation due to turbidity effects. The SSC and SMD measurements allow for a detailed assessment of the dynamics between precipitation and suspended sediment load even though discharge volumes were not measured directly. [ABSTRACT FROM AUTHOR]

• Sediment dynamics of a small watershed in the Northern Apennines was assessed. • The watershed is affected by rill-interrill and calanchi erosion. • A morphometrical characterisation of the basin was performed using a DEM. • A suspended sediments were assessed using a laser diffraction technique. • SSC and SMD were related to the available rainfall data. The volumes and dynamics of suspended sediments drained from a watershed are often unknown, especially in small creeks and tributaries where continuous discharge measurements are seldom available. The objective of this study was to assess in a qualitative and quantitative way the sediment dynamics of a small ungauged watershed in the Northern Apennines, Italy. We analysed and correlated the sediment volume concentration and grain-size distribution of the suspended sediments with the precipitation pattern. The study area is a small ungauged watershed (0.15 km2) that is dominated by intensive soil erosion processes and related landforms. The basin is oriented East-West with the south-facing slopes characterized by badland erosion processes. The north-facing slopes are cultivated and dominated by rill-interrill erosion phenomena. An morphometrical characterization of the basin was performed using a high-resolution DTM with a 1 × 1 m resolution. Subsequently, the physical characteristics of the topsoil were investigated based on grain size laboratory analysis. A detailed NDVI analysis of the vegetation was performed using Sentinel-2A images. Finally, we assessed the suspended sediments at the outlet of the basin using a laser diffraction technique. The Suspended Sediment Volume Concentration (SSC) and the Sauter Mean Diameter (SMD) of the eroded sediments, provide insights into the morphogenetic processes and the sediment transport dynamics of the basin. The measurements were conducted in autumn 2018 after an intense precipitation period and in spring 2019 after a dry phase. The results show a direct relationship between precipitation and SSC with a delay of about 2 h after the most intense precipitation events. Moreover, we reveal that the SMD values are inversely related to the precipitation due to turbidity effects. The SSC and SMD measurements allow for a detailed assessment of the dynamics between precipitation and suspended sediment load even though discharge volumes were not measured directly. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Sinai Peninsula is primarily relying on the groundwater storage from the shallow and deep aquifers to meet the requirements of the current and future agricultural projects. Thus, understanding of the present and future groundwater flow, especially in the northern coastal aquifers, presents a crucial step towards sustainable groundwater management plans in these regions. El-Tina Plain is located in the northwestern corner of the Sinai Peninsula covering an area of about 1600 km2 and bordered by the Mediterranean Sea to the North and the Suez Canal to the West. The rainfall is considered the main source of recharge where the average annual rainfall ranges between 80 to 90 mm. The water levels in the Pleistocene coastal aquifer range from less than one meter at the North to about 4 meters at the south. The groundwater is flowing from the south towards northern and northwestern borders, i.e., towards the Mediterranean Sea and the Suez Canal respectively. As such, the development and exploitation plans in this region are critical due to the freshwater resources are threatened by the risk of seawater intrusion and subsequent severe environmental problems. The present study aimed to determine the optimum groundwater abstraction (i.e., safe yield) to avoid the possible saltwater up-coning using MODFLOW modeling package, which is included in the framework of the Groundwater Modeling System (GMS). A two-dimensional groundwater flow model was adopted utilizing all the relevant datasets including the boundary conditions, aquifer parameters, and hydrological data. Simulation results fit well with the observed measurements and the model was calibrated using a set of conventional statistical error measures such as the bias, the mean absolute error (MAE) and the normalized root mean square error (NRMSE). Multiple scenarios of the anticipated groundwater flow under different stresses including the number of pumping wells and different discharge rates were introduced. Results show that a network of 15 water wells is recommended to be drilled in the region with an optimum abstraction rate that should not exceed 300 m3/day from each well to prevent the risk of seawater intrusion. Our findings can, therefore, contribute to better management of groundwater resources and agricultural practices in the coastal regions and elsewhere. [ABSTRACT FROM AUTHOR]