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Moving Substrate in an Ephemeral Stream Revisited: A Continuing Case Study
Published in Nigel Powers, Dan M. Frangopol, Riadh Al-Mahaidi, Colin Caprani, Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges, 2018
George R. Herrmann, D.W.R.E. Cfm, Theodore G. Cleveland
The Guadalupe Mountains generate orographic rainfall on the mountain slopes themselves, but little of that rain falls in the surrounding desert. Much of the discharge that passes the bridge results from rainfall in the mountains, when rainfall at the site may be completely absent. There are no long-term stream gauges in the area, and rain data is anecdotal. Lack of rainfall statistics by which to model rainfall-runoff, and dissimilarity to other stream gauge sites, makes hydrologic estimation of discharge very difficult or impossible. Interestingly, Guadalupe Arroyo begins high and at extremely steep slopes, but empties into a dry “salt flat” to the west. Gradient vanishes as it approaches the lake.
On the Specification of the Information Available for the Perception and Description of the Natural Terrain
Published in Peter Hancock, John Flach, Jeff Caird, Kim Vicente, Local Applications of the Ecological Approach to Human-Machine Systems, 2018
Robert R. Hoffman, Richard J. Pike
Choosing the “right” or characteristic space-time scale for a particular terrain surface is critical to any remote-sensing investigation (Davis et al., 1991). For most work, pixel sizes or image resolution can range from square meters up to square kilometers. The chosen resolution depends on the phenomena of interest. The spatial and temporal resolving power must capture both homogeneity and heterogeneity of the landscape with respect to its important features and the research objectives (e.g., the size of crowns of particular diseased tree species versus the extent and spectral signature of a salt flat for minerals prospecting).
The use of dynamic soundings in evaluating settlements
Published in A. Verruijt, F.L. Beringen, E.H. De Leeuw, Penetration Testing, 2021
The remainder of the site, at an elevation of +1.1 to +2.0 metres, consisted of a sabkha (salt flat), a highly saline soil with properties governed by an evaporative environment (Akili & Fletcher, 1979). Typically the sabkha had a surface crust a few centimetres thick. Underlying the crust were up to 5 metres of very loose, fine sands, silty sands and very soft silts, and clays, the sands being predominant. There was considerable variation of soil type and density in lateral and vertical directions within the sabkha.
Analysis of roughness performance of chloride-stabilised rural roads
Published in International Journal of Pavement Engineering, 2021
Alelí Osorio-Lird, Alondra Chamorro, Álvaro González
The road construction industry typically uses sodium, magnesium, and calcium chlorides as stabilisation additives to improve road performance. In Chile, magnesium chloride and sodium chloride are the most used additives for road stabilisation in arid areas, where air humidity and annual rainfall are low (i.e. less than 100 mm per year). The additives for inclusion in this study were selected by their availability, physical characteristics, and relatively low cost compared to that of other additives (González et al.2018). Magnesium chloride is a by-product of the non-metallic mining industry and is obtained from evaporation ponds located at Atacama Salt Flat. Large mining companies produce sodium chloride in the north of Chile, primarily from quarrying the Tarapacá Salt Flat. These chlorides were also selected for their hygroscopy, the ability to absorb water from the air, which is the most important physical characteristic of the chlorides used in the study. In addition, chlorides lower vapour pressure, reducing the normal water evaporation rate, thus increasing water retention from the stabilised granular material. This project studied roads in a dry climate, and it is worth noting that the use of chlorides may not be appropriate in climates with high annual rainfall or zones exposed to high air relative humidity for long periods.
Optimised multivariate Gaussians for probabilistic subsurface characterisation
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2019
Mohammad B. Abdulla, Rita L. Sousa, Herbert Einstein, Sara Awadalla
Sabkha is a salt flat. John K. Warren (1989) defined it as marine and continental mudflats where displacive and replacive evaporite minerals are forming in the capillary zone above a saline water table. In general, the Sabkha results from the variation of the evaporation rates of salt water in the soil. The UAE climate is hot during the summer and relatively cool during the winter as it lies close to the Tropic of Cancer. The high temperature of the air and the water in the summer, the strong winds and the low rainfall cause significant evaporation which results in increasing the salinities. Zones with Sabkha are one of the main sources of the geological hazards because of the high concentration of evaporites, such as gypsum, halite and anhydrite, Sabkha layers are prone to heave and/or dissolve when in contact with water, negatively affecting structures on and below the surface.
Relative value of radar and optical data for land cover/use mapping: Peru example
Published in International Journal of Image and Data Fusion, 2018
Table 3 contains the spectral signatures for the various LCLU classes. The values for the TM bands are quite reasonable. There are also significant differences in mean values between the classes in all TM bands. The salt flat has the highest mean values in all bands. The two agricultural classes have very similar patterns in mean values across all TM bands but the second signature has consistently higher values. The visible blue band has relatively high average values in all classes. This is primarily because of the additive effect of the atmosphere. The first mid-infrared band, band 5, has the largest variation in mean values from 84 for the agricultural-1 class to 251 for the salt flat. Not surprisingly, the industrial class has the largest standard deviations because of the variation in features including different roofing materials, as well as roads and open areas. As would be expected there is little variation of the mean thermal band values, band 6, which is also supported by the low standard deviations for this band. The slightly lower band 6 values for the agricultural classes are likely due to the agricultural land being irrigated.