Plough marks as a tool to asses soil erosion: a case study in Axum (Ethiopia)

From the antiquity, the hilly landscape around the city of Axum in northern Ethiopia has been terraced and extensively used for agriculture purposes. The traditional “ard” plough seems to have been introduced in Ethiopia between 1000 and 400 BC. The impact of the plough against stones protruding and/o buried at a depth lower than the tilling depth produces a scratch on their sides or their top. The spatial relationship among plough marks and rock surface orientations gives information on the ploughing direction, whereas, if information about the age of cultivation is provided, the relative height from the present ground surface to the top of the marks can be used to assess soil loss rates. A few parameters to define the plough marks orientation were defined and measured in the field selecting a number of stones with plough marks within a study terrace located in an archaeological area of known age. These parameters are height from the ground, dip, slope and frequency. In this paper plough marks have been used as an innovative method to asses soil erosion rates and to reconstruct the original terrace slope and ploughing direction. The data measured clearly show that the initial terrace slope was steeper than the present one confirming the effectiveness of the traditional terracing practice in soil conservation because of the low soil erosion rates assessed over a so large time interval. For the main time intervals of the Axumite history, corresponding to the rise and fall of the Axumite civilization and to variable conditions of human pressure on the land, the maximum erosion rates inferred is of the order of 3.4 Mg ha-1 yr-1. This result is compared with erosion rates calculated with other methods reported in the literature (e.g. PSIAC) and field measurement on terraces in the same region leading to values almost coinciding with those obtained by the plough marks method

Soil erosion induced by land use changes as determined by plough marks and field evidence in the Aksum area (Ethiopia)

The aim of the research presented here was to analyse soil erosion in response to changes in agricultural and soil conservation practices throughout history. The Aksum area (Tigray, northern Ethiopia) presents favourable conditions for the development of a long-term approach for assessing soil conservation techniques that have been applied for centuries (i.e., since the Aksumite kingdom, 400 BC to 800 AD). These techniques have been maintained until the present day, and parts of the terraced systems of the area are still in use. During the 1970s, social and political events led to a remarkable change in land use patterns, and large arable areas were converted into grazing land, resulting in a significant increase in soil loss. The rates of soil erosion were evaluated based on analyses of the deep scratches (plough marks) left on stones in the soil by the maresha, the ard plough pulled by oxen used in agricultural practices of the area, and the patinas, varnishes and weathering rinds exposed by soil loss after the abandonment of the fields. The study results show average rates of soil erosion of 2.8 t ha−1 y−1 and 65.8 t ha−1 y−1 for the soil conservation conditions under traditional agriculture (long-term observations) and accelerated erosion after abandonment (short-term observations), respectively. A comparison using recently calibrated erosion evaluation techniques conducted to support the field measurements revealed a close correlation between the calculated and recorded data

Albuminuria and insulin resistance in children with biopsy proven non-alcoholic fatty liver disease

Insulin resistance may favor increased urinary albumin excretion (UAE), leading progressively to chronic kidney disease (CKD). A recent study on non-alcoholic fatty liver disease (NAFLD), a condition of insulin resistance, associated this disease with the incidence of CKD in patients with type 2 diabetes. The aim of our study was to determine whether there is an association between insulin resistance and kidney function, based on estimates of UAE and creatinine clearance in children with biopsy-proven NAFLD. Kidney function was assessed in 80 patients with NAFLD and 59 individuals of normal weight matched for age and sex. Insulin resistance was measured by means of the homeostatic model assessment-insulin resistance (HOMA-IR) and limited to NAFLD patients by using the whole-body insulin sensitivity index. The HOMA-IR was found to differ significantly between the two groups (2.69 +/- 1.7 vs. 1.05 +/- 0.45; p = 0.002), while UAE (9.02 +/- 5.8 vs. 8.0 +/- 4.3 mg/24 h; p = 0.9) and creatinine clearance (78 +/- 24 vs. 80 +/- 29 mg/min; p = 0.8) did not. We found a significant but weak inverse correlation between insulin sensitivity and creatinine clearance in NAFLD patients (r (s) = -0.25;p = 0.02). No difference was observed in kidney function between NAFLD children presenting with or without metabolic syndrome, low or normal HDL-cholesterol, and different degrees of histological liver damage (grade of steatosis a parts per thousand yen2, necro-inflammation, and fibrosis). Patients with hypertension had increased levels of UAE (p = 0.04). A longer exposure to insulin resistance may be required to cause the increase in urinary albumin excretion and to enable the detection of the effect of the accelerated atherogenic process most likely occurring in children with fatty liver disease. Longitudinal studies are needed to rule out any causative relationship between insulin resistance and urinary albumin excretion

Long term soil erosion analysis on a terraced system with the support of archaeological data in the area of Aksum (Etiopia)

Landscape evolution in agricultural contexts is primarily the result of soil redistribution processes done by human activity and water erosion. The analysis of such soil dynamics in archaeological areas is useful to understand the evolution of the landscape structures. This study is focused on the area of Aksum (Ethiopia), one of the most relevant archaeological sites in East Africa, where the flourishing and decay of the Aksumite Kingdom (400yBC, 800yAD) took place. It provided favorable conditions for long term approach to the study of soil conservation techniques since they have been maintained from ancient times to present. In the present study, three terrace systems have been surveyed and analysed in terms of soil loss across the last two millennia by physical and archaeological evidences. Tillage and water erosion has been simulated by a long-term expert-system model (LandSoil) (Ciampalini et al., 2011) based on a raster distributed-approach accounting the principal components in soil erosion-deposition processes. The results of model analysis, integrating tillage erosion, diffusive and concentrated erosion have been compared and calibrated with the plough marks technique (Ciampalini et al., 2008; 2011), soil loss computing procedures such as the PSIAC model for Ethiopian Highlands (Negussie et al., 2005) and a reparameterisation of P factor (USLE) for stone-bounds (Desta et al., 2005). This analysis provides values for tillage soil displacement and water erosion comparable with these reported in the literature, accounts for the relative influence of both mechanical and hydrological processes, and confirms the high efficiency of these traditional soil conservation practices

Integration of Satellite InSAR with a Wireless Network of Geotechnical Sensors for Slope Monitoring in Urban Areas: The Pariana Landslide Case (Massa, Italy)

Slow to extremely slow landslides in urban areas may cause severe damage to buildings and infrastructure that can lead to the evacuation of local populations in case of slope accelerations. Monitoring the spatial and temporal evolution of this type of natural hazard represents a major concern for the public authorities in charge of risk management. Pariana, a village with 400 residents located in the Apuan Alps (Massa, Tuscany, Italy), is an example of urban settlement where the population has long been forced to live with considerable slope instability. In the last 30 years, due to the slope movements associated with a slow-moving landslide that has affected a significant portion of the built-up area, several buildings have been damaged, including a school and the provincial road crossing the unstable area, leading to the need for an installation of a slope monitoring system with early warning capabilities, in parallel with the implementation of mitigation works. In this paper, we show how satellite multi-temporal interferometric synthetic aperture radar (MT-InSAR) data can be effectively used when coupled with a wireless sensor network made of several bar extensometers and a borehole inclinometer. In fact, thanks to their wide area coverage and opportunistic nature, satellite InSAR data allow one to clearly identify the spatial distribution of surface movements and their long-term temporal evolution. On the other hand, geotechnical sensors installed on specific elements at risk (e.g., private buildings, retaining walls, etc.), and collected through Wi-Fi dataloggers, provide near real-time data that can be used to identify sudden accelerations in slope movements, subsequently triggering alarms. The integration of those two-monitoring systems has been tested and assessed in Pariana. Results show how a hybrid slope monitoring program based on the two different technologies can be used to effectively monitor slow-moving landslides and to identify sudden accelerations and activate a response plan

STABLE ISOTOPE COMPOSITION OF FOSSIL AHERMATYPIC CORAL CLADOCORA CAESPITOSA (L.) FROM PLEISTOCENE RAISED MARINE TERRACES OF THE LIVORNO AREA (CENTRAL ITALY)

The Livorno coastal area (coastal Tuscany) preserves evidences of several raised marine terraces. Stratigraphically they have been correlated with MIS 5e, 9c and MIS 11 sea-level high stands. However, no direct dating have been performed so far. Thanks of new findings of fossil specimens of ahermatypic coral of Cladocora caespitosa in the terraced units correlated to MIS 5e (“Terrazzo di Livorno”) and MIS 11 (“Terrazzo della Fattoria Pianacce”) we attempted direct dating using the U/Th technique. Moreover, stable isotopes (oxygen and carbon) were used for attempting environmental reconstruction. Dating support the correlation of the “Terrazzo di Livorno” unit with the MIS 5e but are inconsistent for the older unit indicating diagenetic Umobilization. Oxygen stable isotopes suggest warmer condition for the MIS 5e and MIS 11 compared to modern conditions, even if the indetermination on the water isotopic composition of past interglacial (i.e. ice volume) hampers our capacity to quantify this values

Increased frequency of flash floods in Dire Dawa, Ethiopia: change in rainfall intensity or human impact?

In the last decade, Ethiopia has been subjected to an increased frequency of flash floods, especially in the town of Dire Dawa. The results of International Organisations studies point to no evidence of a climate-driven change in the magnitude/frequency of floods, though increases in runoff and risk of floods in East Africa are expected. Since few studies of African climate have considered the temporal variations of daily rainfall and the relationship between rainfall intensity, land use change and flash floods in Ethiopia, this study analyses the recent trends of rainfall intensity across Ethiopia in order to ascertain if the increased frequency of flash floods is paralleled by an increase of daily precipitation. Secondly, the relative role of rainfall intensity and land use change in augmenting the frequency of flash floods is investigated in the Dechatu River flowing through the town of Dire Dawa. Results indicate that the increase in rainfall intensity is larger than the increase in runoff generated by land use change with the former being likely the more important factor in controlling the increased frequency of flash flood in Dire Dawa

The contribution of satellite SAR-derived displacement measurements in landslide risk management practices

Landslides are common phenomena that occur worldwide and are a main cause of loss of life and damage to property. The hazards associated with landslides are a challenging concern in many countries, including Italy. Over the last 15 years, an increasing number of applications have aimed to demonstrate the applicability of images captured by space-borne Synthetic Aperture Radar (SAR) sensors in slope instability investigations. InSAR (SAR interferometry) is currently one of the most exploited techniques for the assessment of ground displacements, and it is becoming a consolidated tool for Civil Protection institutions in addressing landslide risk. This paper presents a subset of the results obtained in Italy within the framework of SAR-based programmes and applications intended to test the potential application of C- and X-band satellite interferometry during different Civil Protection activities (namely prevention, prevision, emergency response and post-emergency phases) performed to manage landslide risk. Analysis of satellite SAR data is demonstrated to play a major role in the investigation of landslide-related events at different stages, including detection, mapping, monitoring, characterization and prediction. In addition, this paper also discusses the limitations that still exist and must be overcome in the coming years to manage the transition of satellite SAR systems towards complete operational use in landslide risk management practices