Development of Desertification Indicators for Desertification Monitoring from Landsat Images Using Python Programming

Nowadays, desertification is one of the most serious environment socioeconomic issues and sand dune advances are a major threat that causes desertification. Wadi El-Rayan is one of the areas facing severe dune migration. Therefore, it's important to monitor desertification and study sand dune migration in this area. Image differencing for the years 2000 (Landsat ETM+) and 2019 (OLI images) and Bi-temporal layer stacking was performed. It was found that image differencing is a superior method to get changes of the study area compared to the visual method (Bi-temporal layer stacking). This research develops a quantitative technique for desertification assessment by developing indicators using Landsat images. Spatial distribution of the movement of sand dunes using some spectral indices (NDVI, BSI, LDI, and LST) was studied and a Python script was developed to calculate these indices. The results show that NDVI and BSI indices are the best indices in the identification and detection of vegetation. It was found that mobile sand dunes on the southern side of the lower Wadi El-Rayan Lake caused filling up of large part of the lower lake. The indices results show that sand movement decreased the size of the lower Wadi El-Rayan Lake and there are reclamation activities in the west of the lower lake. The results show that a good result could be achieved from the developed codes compared to ready-made software (ENVI 5).

Fundamental issues in Japan’s management system of coast for preventing beach erosion

When an offshore or port breakwater is constructed on a coast, beach erosion often occurs on nearby beaches of the breakwater due to the wave diffraction effect of the breakwater associated with the formation of a wave-shelter zone, because longshore sand transport is triggered from outside to inside the wave-shelter zone. Similarly, when unidirectional longshore sand transport is blocked by a breakwater, beach erosion will occur downcoast. In these cases, longshore sand movement is the key factor. Another aspect is arisen from the management system of the land near a coast subject to such longshore sand movement. In Japan, the management of coastal land is under the jurisdiction of several agencies. When sand is transported alongshore across 2 management areas, the sand right belongs to the agency administrating the area to which the sand is deposited, and the agency administrating the area from which the sand originated has no right. Thus, this leads to uncoordinated solution to erosion problems, because longshore sand can freely move across the boundaries of coastal management areas. In this study, these issues were studied through real examples. Even though the accuracy of the predictive model of beach changes is increased, implementing fundamental changes of the coastal condition is difficult when this issue is unsolved as it is.

Numerical Investigation of Wind Erosion to the Grooved Concrete Wall Surface under a Wind-Blown Sand Movement

Wind erosion to the grooved concrete wall surface under a wind-blown sand movement was numerically studied. Particularly, the influencing factors that affect the wind erosion to the grooved concrete wall surface were systematically investigated by using the RNG k − ε turbulence model combined with the discrete phase model (DPM). It was found that, under a relatively low impact angle, the damage mechanism to the grooved wall surface is wind-blown sand impact, and the erosion rates of the grooved wall surfaces are higher than those of the smooth wall surfaces. By contrast, under a relatively high impact angle, the damage mechanism to the grooved wall surface transfers to the microcutting effect, and the erosion rates show an opposite trend. The optimization rates between the erosion of grooved and smooth wall surfaces increase with increasing groove size or groove number. However, the damage mechanism to the grooved wall surface is hardly changed by expanding the groove area. The erosion rate distribution and the optimization rates of the groove wall surfaces are not significantly changed by adjusting the spacing between the grooves alone. When the groove shape changes from semicircular to rectangular, the erosion rate distribution is significantly changed, and the wear resistance of the changed grooved wall surface gets better.

Stability analysis of concrete block retaining wall based on a scaled laboratory

A concrete block retaining wall is supported by its weight. This block retaining wall structure has some advantages, including lower construction costs, a water-permeable construction that produces less water pressure behind the wall, and a more flexible construction because it can follow the ground's contours. Rankine's theory is usually used to design this block retaining wall. According to this theory, the failure pattern behind the wall forms an angle of 450 + • /2 with the horizontal plane. The laboratory tests indicate that the pattern of failure or the pattern of sand movement behind the wall is similar to the letter S. From the sandy soil of failure pattern curve, look for a functional equation approximating the pattern. The equation of the function obtained is an equation of the third-order function. An analysis of the sliding, overturning, and overall stability block retaining wall is based on this equation of the cube function. Analysis for overall stability using the method of slices, dividing the failure area by several slices. These function equation order three is needed to get the area and length failure.

HYDRAULIC APPROACH TO SHORELINE CHANGE DUE TO SUBMERGED BREAKWATER

The items of investigation include wave induced current, wave height, beach profile, shoreline change, etc. The investigation has been performed seasonally. After the construction of submerged breakwaters, a tombolo was generated behind the submerged breakwaters. This caused beach erosion in the nearby areas. Rip currents are mainly generated near submerged breakwaters, which plays a role in the transportation of sand in the offshore direction. In order to analyze the sand movement, numerical analysis was conducted. The analysis indicated that a strong rip current is generated near submerged breakwaters.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5p2wiNSMKlM

The Use of SAR Offset Tracking for Detecting Sand Dune Movement in Sudan

Sand movement is one of the main environmental hazards in Northern Sudan that threaten livelihood and rural communities. This paper investigates for the first time the use of the Synthetic Aperture Radar (SAR) offset tracking technique for detecting sand movement in Northern Sudan, and distinguishes the impact of the movement influencing factors: wind speed/direction, vegetation and topography. High-resolution images from the Sentinel-1 satellite were used for the generation of displacement maps. Three different dune fields with different characteristics were investigated for a study period between 4 June and 14 October 2017 (133 days). Dune field 1 is vegetated and near a built-up area, dune field 2 is in an open environment with sand dunes overlaying rocky substrate, and dune field 3 is located near mountains. The cumulative east displacement over the study period was 1.8 m, −1.1 m and 4.8 m for the three dune fields, respectively, while the cumulative north displacement was 0.7 m, 2.9 m and 4.2 m. Large movement is detected in the non-vegetated dune fields, with an average dune velocity of 0.18 m/d, while the vegetated dune field had a velocity of 0.09 m/d, which emphasizes the fact that vegetation is an effective stabiliser of dune movement. The pixel offset results showed a positive correlation between the wind speed/direction and the dune movement. In addition to vegetation, topography also played a major role in diverting the direction of the blown sand mainly near the edges to the mountains and the vegetation barriers. This technique showed high competency in monitoring the movement of sand dunes, in addition to identifying areas exposed to large sand drifting as a risk mapping technique.

Forecast of Changes in the Condition of the Beach Condition of the City of Mykolaiv Under Influence Natural Factors

Purpose. The forecast of a condition of a beach of the city of Nikolayev, the general offers of measures of its protection against degradation. Methods. The forecast of a condition of a beach of the city of Nikolayev is made with use of methods of mathematical statistics and mathematical modeling, the comparative analysis, cartographic and graph analytical researches. Results. The beach of the city of Nikolayev is a strip of coast of the big water object where features of reforming of coasts of reservoirs and the rivers united. The location of the beach on the convex shore of the Bug estuary creates the conditions for the accumulation of sand due to the coastal movement of sediments downstream. However, the width of the estuary and the depth contribute to the formation of wind turbulence in the sector S-Z-Pn, which can destroy the beach. On the beach during the spring floods or in severe down pouring phenomena, long-coastal movement of sands in large volumes is possible depending on the duration of strong currents, but the transportation of sediments along the beach does not significantly affect changes in the outline of its coastal slope. Significant destruction of the beach can occur from storms of rare recurrence in the sector S-SW. Western frontal storms form a profile of relative dynamic equilibrium and contribute to the movement of sands to depth. When the waves approach at an angle to the shoreline is the longitudinal transport of sand. Protection of the beach from erosion can be done by passive or active methods. Further research will focus on a quantitative analysis of the scenario of sand movement along the beach with its accumulation on the protruding part of the beach (point C) and washing away the accumulated sand to a depth under the influence of western storms. Conclusion. Without acceptance of special measures for protection the beach of Nikolayev in the future will degrade.