Modelling aeolian sand transport and morphological development in two beach nourishment areas

The aeolian sand transport model SAFE and the air flow model HILL were applied to evaluate cross‐shore changes at two nourished beaches and adjacent dunes and to identify the response of aeolian sand transport and morphology to several nourishment design parameters and fill characteristics. The main input of the model consisted of data on the sediment, tide and meteorological conditions, and of half‐yearly measured characteristics of topography, vegetation and sand fences. The cross‐shore profiles generated by SAFE–HILL were compared to measured cross‐shore profiles. The patterns of erosion and deposition, and the morphological development corresponded. In general, the rates of aeolian sand transport were overestimated. The impact of parameters that are related to beach nourishment (namely grain size, adaptation length and beach topography) on profile development was evaluated. Grain size affected the aeolian sand transport rate to the foredunes, and therefore the morphology. Adaptation length, which is a measure of the distance over which sediment transport adapts to a new equilibrium condition, affected the topography of the beach in particular. The topography of a beach nourishment had limited impact on both aeolian sand transport rate and morphology. Copyright © 2000 John Wiley & Sons, Ltd.     

Flow prediction in high altitude ungauged catchments: A case study in the Italian Alps (Pantano Basin,Adamello Group)

We develop a simple model to evaluate the daily flow discharges in the ablation season for the 11 km² Pantano basin in the Retiche Italian Alps, based upon the data gathered during a three years field campaign. The Pantano basin embeds the Venerocolo debris covered and the Avio debris free glaciers, covering 2.14 km² in the Adamello Group, where the widest Italian glacier Adamello is located. First, degree-day models based upon air temperature are tuned to calculate snow and ice melt at daily scale. Glaciers’ meteorological data are collected from an automatic weather station (AWS), operating on the glacier during summer 2007. The melt factors in the debris covered areas of the glacier are estimated against debris thickness, using a data driven parameterization. The flow discharge from the catchment is estimated using semi distributed flow routing for the ablation seasons of four years, from 2006 to 2009. The predicted discharges are compared to those derived from inverse reservoir's routing at the Benedetto lake, catching the basin outflow. The proposed approach is valuable as a tool to investigate the hydrology of poorly gauged glacierized areas, including those with debris covered ice, widely diffused and yet poorly understood. Pending accurate parameterization the approach is usable for water resources evaluation and for long term assessment of the climate change impact on the glacierized areas within the Alps.     

Stochastic modelling of soil moisture dynamics in a grassland of Qilian Mountain at point scale

Stochastic modeling of soil moisture dynamics is crucial to the quantitative understanding of plant responses to water stresses,hydrological control of nutrient cycling processes,water competition among plants,and some other ecological dynamics,and thus has become a hotspot in ecohydrology at present.In this paper,we based on the continuously monitored data of soil moisture during 2002―2005 and daily precipitation date of 1992―2006,and tried to make a probabilistic analysis of soil moisture dynamics at point scale in a grassland of Qilian Mountain by integrating the stochastic model improved by Laio and the Monte Carlo method.The results show that the inter-annual variations for the soil moisture patterns at different depths are very significant,and that the coefficient of variance(CV) of surface soil moisture(20 cm) is almost continually kept at about 0.23 whether in the rich or poor rainy years.Interestingly,it has been found that the maximal CV of soil moisture has not always appeared at the surface layer.Comparison of the analytically derived soil moisture probability density function(PDF) with the statistical distribution of the observed soil moisture data suggests that the stochastic model can reasonably describe and predict the soil moisture dynamics of the grassland in Qilian Mountain at point scale.By extracting the statistical information of the historical precipitation data in 1994―2006,and inputting them into the stochastic model,we analytically derived the long-term soil moisture PDF without considering the inter-annual climate fluctuations,and then numerically derived the one when considering the inter-annual fluctuation effects in combination with a Monte-Carlo procedure.It was found that,though the peak position of the probability density distribution significantly moved towards drought when considering the disturbance forces,and its width was narrowed,accordingly its peak value was increased,no significant bimodality was observed in the soil moisture dynamics under the given intensity of random fluctuation disturbance.     

柴达木盆地东南部土壤风蚀研究

柴达木盆地东南部土壤风蚀风洞模拟实验结果表明,土壤风蚀强度随风力作用和下垫面因子不同而不同。净风对土壤风蚀作用较小,但在挟沙风作用下,风蚀强烈。地表类型不同风蚀强度变化很大,流动沙地是耕地(小麦留茬)的数百倍。土壤质地不同起沙风速不同,细沙和极细沙比例越高风蚀量越大。翻耕地与未翻耕地风蚀变化悬殊,翻耕地风蚀量是未翻耕地的10倍以上。自然植被和人为留茬均有抑制风蚀的作用。     

B-polarization induction in two thin half-sheets coupled to the mantle by a conducting crust—II. Solution by the mode-matching method, the fields above the conductors, and example results

The mode-matching method is used to obtain an exact analytical solution to the problem of B -polarization induction in two adjacent thin half-sheets, lying on a conducting layer that is terminated by a perfect conductor at finite depth. These components of the model represent, respectively, the Earth's conducting surface layers, crust, and mantle. In dimensionless variables, the model has three independent parameters, these being the two thin-sheet conductances and the layer thickness. The mode-matching solution obtained in this paper is shown to be identical lo that derived via the Wiener-Hopf method in a companion paper (Dawson 1996), and so provides additional verification of that solution. As was shown in the companion paper, the solution for the present model contains, as special limiting cases, those for three models considered earlier by various authors. The second part of the present paper addresses the solutions for the electric fields in the non-conducting half-space above the conductors, which represents the atmosphere. In the final part, sample numerical calculations are presented to illustrate the solution.     

Modelling the Venice Lagoon

In this paper, an overview is given on the modelling activities at the National Research Council in Venice (ISDGM-CNR) concerning the Venice Lagoon. A short history of former modelling efforts is given. A finite element hydrodynamic model is presented that has been created especially for the Venice Lagoon. This model has been applied to various situations. Residual currents have been computed for one year. A specific storm surge event has been simulated with spatially varying real winds. A transport diffusion model has been applied to model the impact of a treatment plant on the central lagoon. And a sub-basin has been modeled with a high resolution grid.     

Neural dynamic modelling on earthquake magnitude series

Earthquake magnitude prediction is of vital importance for human safety. The earthquake is a very complicated and non-linear dynamic process. It cannot be described adequately by any deterministic models. In this paper a neural dynamic modelling for earthquake magnitude prediction is reported. Historical records of earthquake magnitude series are used to construct the optimal non-linear dynamic model, and the consequent outcome of the earthquake behaviour is then predicted by this model. In turn, the latest recorded data set can be fed back to improve the accuracy of the neural dynamic model. The modelling of experiments of three earthquake magnitude series in China and Japan and their extrapolated predictions are included in this paper. The values predicted by extrapolation are in good agreement with the historical data.