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More settlements will suffer as heavy rains and unregulated construction destabilize slopes in the tropics, models show. More settlements will suffer as heavy rains and unregulated construction destabilize slopes in the tropics, models show. Low-angle view of people gathering at a damaged building at a mudslide site in Freetown, Sierra Leone

The application of light detection and ranging (LiDAR), a laser-based remote-sensing technology that is capable of penetrating overlying vegetation and forest canopies, is generating a fundamental shift in Mesoamerican archaeology and has the potential to transform research in forested areas world-wide. Much as radiocarbon dating that half a century ago moved archaeology forward by grounding archaeological remains in time, LiDAR is proving to be a catalyst for an improved spatial understanding of the past. With LiDAR, ancient societies can be contextualized within a fully defined landscape. Interpretations about the scale and organization of densely forested sites no longer are constrained by sample size, as they were when mapping required laborious on-ground survey. The ability to articulate ancient landscapes fully permits a better understanding of the complexity of ancient Mesoamerican urbanism and also aids in modern conservation efforts. The importance of this geospatial innovation is demonstrated with newly acquired LiDAR data from the archaeological sites of Caracol, Cayo, Belize and Angamuco, Michoacán, Mexico. These data illustrate the potential of technology to act as a catalytic enabler of rapid transformational change in archaeological research and interpretation and also underscore the value of on-the-ground archaeological investigation in validating and contextualizing results.

GaAs thermal smoothing at temperatures T ≤ 650°C under conditions close to equilibrium yields surfaces with atomically smooth terraces separated by steps of monatomic height. At higher temperatures T ≥ 700°C, surface smoothing changes to roughening. In the present paper, thermal roughening of a step-terraced surface caused by atomic step flow around step pinning centers is studied using Monte-Carlo simulation. It is proved that the Schwöbel barrier is necessary for step bunching in the presence of step pinning centers. The lower limit of the Schwöbel barrier ES = 0.4 eV is estimated for the GaAs(001) surface.

East Africa is highly reliant on agriculture and has high rates of soil erosion which negatively impact agricultural yields. Climate projections suggest that rainfall intensity will increase in East Africa, which is likely to increase soil erosion. Soil erosion estimates require information on rainfall erosivity, which is calculated using sub-daily storm characteristics that are known to be biased in traditional parameterized convection climate models. Convection-permitting climate models, which are run at higher resolution to negate the need for convection parameterization, generally better represent rainfall intensity and frequency. We use a novel convection-permitting pan-Africa regional climate model (CP4A) to estimate rainfall erosivity in Tanzania and Malawi, and compare it to its parameterized counterpart (P25), to determine if there is a benefit to using convection-permitting climate models to look at rainfall erosivity. We use eight year historical and end-of-century (RCP8.5) climate simulations to examine the impact of climate change on soil erosion in Tanzania and Malawi based on rainfall erosivity estimates from CP4A and P25 applied to the Revised Universal Soil Loss Equation. The effectiveness of soil conservation measures was also evaluated. Rainfall erosivity was lower in P25 than in CP4A and was a poorer match to observational storm characteristics, even after bias-correction. These results suggest that parameterized convection regional and global climate models might under-estimate rainfall erosivity, and the associated soil erosion. We found high values of present day erosion in mountainous regions in Tanzania and Malawi in CP4A. Under climate change, areas at high risk of soil erosion expanded due to increases in rainfall intensity in CP4A. Terracing was less effective at reducing soil erosion risk in the future than in the present day, and more extensive soil management may be required to manage soil erosion and reduce the negative impacts of soil erosion on agriculture.

The application of lidar remote-sensing technology has revolutionized the practice of settlement and landscape archaeology, perhaps nowhere more so than in the Maya lowlands. This contribution presents a substantial lidar dataset from the Puuc region of Yucatan, Mexico, a cultural subregion of the ancient Maya and a distinct physiographic zone within the Yucatan peninsula. Despite the high density of known sites, no large site has been fully surveyed, and little is known about intersite demography. Lidar technology allows determination of settlement distribution for the first time, showing that population was elevated but nucleated, although without any evidence of defensive features. Population estimates suggest a region among the most densely settled within the Maya lowlands, though hinterland levels are modest. Lacking natural bodies of surface water, the ancient Puuc inhabitants relied upon various storage technologies, primarily chultuns (cisterns) and aguadas (natural or modified reservoirs for potable water). Both are visible in the lidar imagery, allowing calculation of aguada capacities by means of GIS software. The imagery also demonstrates an intensive and widespread stone working industry. Ovens visible in the imagery were probably used for the production of lime, used for construction purposes and perhaps also as a softening agent for maize. Quarries can also be discerned, including in some cases substantial portions of entire hills. With respect to agriculture, terrain classification permits identification of patches of prime cultivable land and calculation of their extents. Lidar imagery also provides the first unequivocal evidence for terracing in the Puuc, indeed in all northern Yucatan. Finally, several types of civic architecture and architectural complexes are visible, including four large acropolises probably dating to the Middle Formative period (700–450 B.C.). Later instances of civic architecture include numerous Early Puuc Civic Complexes, suggesting a common form of civic organization at the beginning of the Late Classic demographic surge, (A.D. 600–750).

Identifying vulnerable areas to erosion within the watershed and implementing best management practices (BMPs) are crucial steps in mitigating watershed degradation by minimizing sediment yields. The present study evaluates and identifies the BMPs in the Seybouse basin, northeastern Algeria, using the Soil and Water Assessment Tool (SWAT) model. After successful calibration and validation, the model demonstrated a satisfactory ability to simulate monthly discharge and sediment. Then, the calibrated model was employed to evaluate the efficacy of diverse management practices in sediment control. In the SWAT, three soil and conservation practices, as well as vegetated filter strips (VFSs), grade stabilization structures (GSSs), and terracing were evaluated. The average annual sediment yield in the Seybouse watershed is determined to be 14.43 t/ha year, constituting 71% of the total soil loss. VFS demonstrated a sediment reduction of 37.30%, GSS 20.40%, and terracing 42.30%. Among these strategies, terracing results in the greatest reduction, followed by VFS. The results of this study area can be useful for informed decision-making regarding optimal watershed management strategies.

Terraced agricultural landscapes in Africa are remarkable feats of human engineering and social organization, enabling the conservation of soil and water and the cultivation of food. Indigenous terraced landscapes are all the more valuable because they have been produced by the people themselves and maintained for several hundred years, evidencing a valuable degree of sustainability. Yet until this book, there have been few accounts of how such landscapes in Africa are produced and maintained over time. Taking a period of approximately a hundred years, 'Living Terraces' is both an ethnography and history of the terraces of Konso in southern Ethiopia. It traces the way Konso agriculture and landscape has been produced and managed in close relationship with broader changes in Konso political and cultural lives. In shedding new light on the relationships between landscapes, livelihoods, culture and development, the book demonstrates the embeddedness of social institutions in areas of social, cultural, religious and political life, showing that social institutions cannot easily be abstracted, replicated or used instrumentally for development purposes. The result is a call for an approach to social institutions, so vital to development, which centralizes a study of culture, history and power in the analysis. ELIZABETH E. WATSON is a Lecturer in the Department of Geography, University of Cambridge.

In arid areas prone to desertification and soil erosion, the effectiveness of radical bench terracing in reducing drought risk is dependent on its correct implementation. However, the relationship between proper terracing implementation and the landscape capacity of holding soil moisture is still not understood. Moreover, spatial patterns of Soil Water Content (SWC) within the same terraced hillslope are weakly studied. The present paper analyses SWC variations in four newly implemented terraced sites in Tigray Region, Ethiopia. In all sites, terraced areas show SWC significantly higher than non-terraced ones, with the lower part of the terraced hillslope more humid than the others. A Multiple Linear Regression (MLR) analysis highlighted significant dependency of SWC from the date of analysis, the position in the terraced slope, and its significant positive correlation with the percent of Water Stable Aggregates (WSA) analyzed at the study sites. Since high soil disturbance induces low soil aggregates stability, this result shows how low soil disturbance can significantly increase SWC of radical terraces. Overall, the results of the present paper testify the good performances of bench terraces in Northern Ethiopia in terms of soil water conservation, and can represent a benchmark study informing future terracing implementation in some arid and semi-arid agricultural areas of the world.

Sediment yield estimation along with identification of soil erosion mechanisms is essential for developing sophisticated management approaches, assessing, and balancing different management scenarios and prioritizing better soil and water conservation planning and management. At the watershed scale, land management practices are commonly utilized to minimize sediment loads. The goal of this research was to estimate sediment yield and prioritize the spatial dispersion of sediment-producing hotspot areas in the Nashe catchment using the Soil and Water Assessment Tool (SWAT). Moreover, to reduce catchment sediment output, this study also aims to assess the effectiveness of certain management practices. For calibration and validation of the model, monthly stream flow and sediment data were utilized. The model performance indicators show good agreement between measured and simulated stream flow and sediment yields. The study examined four best management practice (BMP) scenarios for the catchment’s designated sub-watersheds: S0 (baseline scenario), S1 (filter strip), S2 (stone/soil bunds), S3 (contouring), and S4 (terracing). According to the SWAT model result, the watershed’s mean yearly sediment output was 25.96 t/ha. yr. under baseline circumstances. The model also revealed areas producing the maximum sediment quantities indicating the model’s effectiveness for implementing and evaluating the sensitivity of sediment yield to various management strategies. At the watershed scale, treating the watershed with various management scenarios S1, S2, S3, and S4 decreased average annual sediment yield by 34.88%, 57.98%, 39.55%, and 54.77%, respectively. The implementations of the soil/stone bund and terracing scenarios resulted in the maximum sediment yield reduction. The findings of this study will help policymakers to make better and well-informed decisions regarding suitable land use activities and best management strategies.

This study aimed to clarify spatial structure of terraced paddy fields in Desa Bayan located in Lombok Island, Indonesia as an example of cultural landscape of the island. The survey extent was defined by collecting up all waterways from a water source in a sacred forest ( Hutan Adat ) which supply water to traditional paddy fields called Sawah Adat . Location of other irrigation facilities such as intakes and water gates, as well as land ownership within a specific area including paddies owned by a traditional chief ( Kepala Adat ) were collected to understand its spatial characteristics. The findings were summarized as below: 1) Waterways were split into several channels to formulate clusters of paddy fields as a unit of water supply area, 2) size of paddy fields was not consistent but varies based on geographical condition, 3) a set of paddy fields were owned by individual residents not only from Desa Bayan but also from other villages, 4) each set of paddy fields contained a hut which was used not only for resting but also for periodical ceremonies, 5) there was a set of paddy fields owned by a village chief ( Kepala Desa ) from generation to generation which receives water from other paddy fields preferentially, 6) basic structure of the landscape is defined by waterways but the major factors of cultural landscape could be summarized as continuous paddy fields, spaced-out huts, trees along waterways and forests surrounding the entire area.