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PFR model and GiT for landslide susceptibility mapping: a case study from Central Alborz, Iran 总被引：2，自引：0，他引：2
In northern parts of Iran such as the Alborz Mountain belt, frequent landslides occur due to a combination of climate and geologic conditions with high tectonic activities. This results in millions of dollars of financial damages annually excluding casualties and unrecoverable resources. This paper evaluates the landslide susceptible areas in Central Alborz using the probabilistic frequency ratio (PFR) model and Geo-information Technology (GiT). The landslide location map in this study has been generated based on image elements interpreted from IRS satellite data and field observations. The display, manipulation and analysis have been carried out to evaluate layers such as geology, geomorphology, soil, slope, aspect, land use, distance from faults, lineaments, roads and drainages. The validation group of actual landslides and relative operation curve method has been used to increase the accuracy of the final landslide susceptibility map. The area under the curve evaluates how well the method predicts landslides. The results showed a satisfactory agreement of 91% between prepared susceptibility map and existing data on landslide locations. 相似文献
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Experimental study has been carried out under a clear-water scour condition to explore the local scour around semi-elliptical model bridge abutments with armor-layer bed, compared with the local scour process around semi-circular abutment. Two types of model bridge abutments, namely semi-elliptical and semi-circular abutments have been used in this experimental study. The model abutments had a ratio of streamwise length of abutment to the length of abutment transverse to the flow of 2 for semi-circular abutments and 3 for semi-elliptical abutments. In total, 50 Experiments have been designed and conducted under different flow conditions such as bed shear velocities, flow depth, and dimensions of bridge abutment model, as well as grain size of the bed material. Based on these experiments, the scour process around bridge abutments has been assessed. The dependence of the equilibrium scour depth of the scour hole on hydraulic variables has been studied. Empirical equation describing the equilibrium scour depth of the scour hole around bridge abutments has been developed. 相似文献
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Moslem?Borji Arash?MalekianEmail author Ali?Salajegheh Mehrnoosh?Ghadimi 《Arabian Journal of Geosciences》2016,9(19):725
In this study, the preprocessing of the gamma test was used to select the appropriate input combination into two models including the support vector regression (SVR) model and artificial neural networks (ANNs) to predict the stream flow drought index (SDI) of different timescales (i.e., 3, 6, 9, 12, and 24 months) in Latian watershed, Iran, which is one of the most important sources of water for the large metropolitan Tehran. The variables used included SDI t , SDI t ? 1, SDI t ? 2, SDI t ? 3, and SDI t ? 4 monthly delays. Two variables including SDI t and SDI t ? 1 with lower gamma values were identified as the most optimal combination of variables in all drought timescales. The results showed that the gamma test was able to correctly identify the right combination for the forecasting of 6, 9, and 12 months SDI using the ANN model. Also, the gamma test was considered in selecting the appropriate inputs for identifying the values of 9, 12, and 24 months SDI in SVR. The support vector machine approach showed a better efficiency in the forecast of long-term droughts compared to the artificial neural network. In total, among forecasts made for 30 scenarios, the support vector machine model only in scenario 3 of SDI3, scenario 1 of SDI6, and scenarios 2 and 3 of SDI24 represented poorer efficiency compared to the artificial neural network (MLP layer), but in other scenarios, the results of SVR had better efficiency. 相似文献
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Marcelo E. Lago Fernando Miralles-Wilhelm Mehrnoosh Mahmoudi Vic Engel 《Advances in water resources》2010
A numerical model has been developed to simulate the spatiotemporal patterning of the ridge and slough landscape in wetlands, characterized by crests (ridges) and valleys (sloughs) that are elongated parallel to the direction of water flow. The model formulation consists of governing equations for integrated surface water and groundwater flow, sediment transport, and soil accretion, as well as litter production by vegetation growth. The model simulations show how the spatial pattern self-organizes over time with the generation of ridges and sloughs through sediment deposition and erosion driven by the water flow field. The spatial and temporal distributions of the water depth, flow rates and sediment transport processes are caused by differential flow due to vegetation and topography heterogeneities. The model was parameterized with values that are representative of the Everglades wetland in the southern portion of the Florida peninsula in the USA. Model simulation sensitivity was tested with respect to numerical grid size, lateral vegetation growth and the rate of litter production. The characteristic wavelengths of the pattern in the directions along and perpendicular to flow that are simulated with this model develop over time into ridge and slough shapes that resemble field observations. Also, the simulated elevation differences between the ridges and sloughs are of the same order of those typically found in the field. The width of ridges and sloughs was found to be controlled by a lateral vegetation growth distance parameter in a simplified formulation of vegetation growth, which complements earlier modeling results in which a differential peat accretion mechanism alone did not reproduce observations of ridge and slough lateral wavelengths. The results of this work suggest that ridge and slough patterning occurs as a result of vegetation's ability to grow laterally, enhancing sediment deposition in ridge areas, balanced by increased sediment erosion in slough areas to satisfy flow continuity. The interplay between sediment transport, water flow and vegetation and soil dynamic processes needs to be explored further through detailed field experiments, using a model formulation such as the one developed in this work to guide data collection and interpretation. This should be one of the focus areas of future investigations of pattern formation and stability in ridge and slough areas. 相似文献
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