Analysis of flood causes and associated socio-economic damages in the Hindukush region

Pakistan is exposed to numerous hazards, but the problem of recurrent floods has been causing massive losses to lives and other properties. Swat valley is no exception to it. In this paper, an attempt has been made to analyse the causes and associated socio-economic impacts of floods on the Swat valley, Pakistan. Swat valley falls in the Hindukush region, North-west-Pakistan. The valley has been studied with special reference to its physical and socio-economic environment. Similarly, three-sample villages were also randomly selected from the active floodplain for micro-level analysis. The sample villages include Ningolai, Delay and Ghureijo. All the three-sample communities are located on the right bank of river Swat. This area is located in the active flood zone of Swat valley. The analysis revealed that in the study area, floods occur during summer season, which is mainly caused by heavy rainfall as well as rapid melting of snow and glacier. Besides these, there are some floods intensifying factors, which accelerate intensity of floods and enhance resultant damages in the valley. It was found that during flood season, water overflows the natural levees and trigger tremendous loses to housing, agricultural land, standing crops and other properties. The flood-related Government Departments have only implemented limited structural mitigation measures. However, in addition to structural measure, land-use zoning and flood abatement strategies would largely help in reducing the adverse consequences of this recurrent phenomenon.     

An empirical model for salinity intrusion in alluvial estuaries

The main parameters that affect the salinity intrusion in estuaries are their geometric, hydrologic and hydrodynamic characteristics. The recognition of effective parameters and understanding their roles in the salinity intrusion are required for estuarine water management. In this study, the governing equations of the salinity intrusion processes were scaled to derive the effective dimensionless parameters. Then, a previously verified model, CE-QUAL-W2, was utilized as a virtual laboratory to investigate the effects of different governing parameters on the salinity intrusion. Analysis of the results showed that logarithmic functions can be used to describe the effect of dimensionless parameters obtained by scaling of governing equations. Finally, a formula was suggested to predict the salinity intrusion length based on geometrical and hydrodynamic characteristics of alluvial estuaries.     

Impact of tailings dam failure on spatial features of copper contamination (Mazraeh mine area,Iran)

Mining activities pose a potential risk of metal contamination around mining sites. On May 6, 2010, a tailings dam failure of the Mazraeh copper mine near Ahar in East Azerbaijan province, Iran, released vast amounts of mine wastes. To better understand the magnitude of copper contamination in the waste-affected soils, it is important to assess the spatial distribution of soil copper content at unsampled points. A total of 30 soil samples and their surficial sediments together with the 6 uncontaminated control samples (0–10 and 10–30 cm) were collected along the stream flow that joined Ahar-Chai River. Some of soil properties as well as total copper concentration were determined in all samples. The mean value of the latter in the surface contaminated soils was found to be approximately two times more than controls. Furthermore, the mean concentration of copper in the surface loaded material was 10 times more than the soils. High copper concentrations were observed in surficial sediments of the soils near the broken tailings dam. The Inverse Distance Weighting (IDW) method was employed in data analysis. The spherical and Gaussian semivariogram models were properly fitted to the data of copper contents in soils and surficial sediments.     

Provenance, tectonics and source weathering of modern fluvial sediments of the Brahmaputra–Jamuna River, Bangladesh: Inference from geochemistry

This present study describes the elemental geochemistry of fluvial sediments in the Kurigram (upstream) to Sirajganj–Tangail (downstream) section of the Brahmaputra–Jamuna River, Bangladesh, with the aim of evaluating their provenance, weathering and tectonic setting. Petrographically, the sediments are rich in quartz (68%), followed by feldspars (8.5%) and lithic grains (7%). The bulk sediment chemistry is influenced by grain size. Concentrations of TiO₂, Fe₂O₃, MgO, K₂O, P₂O₅, Rb, Nb, Cr, V, Y, and, Ce, Th and Ga slightly decrease with increasing SiO₂/Al₂O₃ and grain size, suggesting clay matrix control. In contrast, concentrations of CaO, Na₂O, Sr and Pb increase with increasing SiO₂/Al₂O₃ and grain size, suggesting residence of these substances in feldspar. Decrease in Zr as grain size increases is likely controlled both by clay matrix and heavy minerals. In addition, heavy minerals' sorting also influences Ce, Th, Y and Cr abundances in some samples. The sediments are predominantly quartzose in composition with abundant low-grade metamorphic and sedimentary lithics, low feldspars and trace volcanic detritus, indicating a quartzose recycled orogen province as a source of the sediments. Discriminant diagrams together with immobile element ratio plots show that, the Brahmaputra–Jamuna River sediments are mostly derived from rocks formed in an active continental margin. Moreover, the rare earth element ratios as well as chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies indicate derivation of the sediments of Brahmaputra–Jamuna River from felsic rock sources of upper continental crust (UCC). The chemical indices of alteration suggest that Brahmaputra–Jamuna River sediments are chemically immature and experienced low chemical weathering effects. In the A–CN–K ternary diagram, most of the samples close to the plagioclase–K-feldspar join line and to the UCC plot, and in the field of various lithologies of Higher Himalayan Crystalline Series, suggesting that rocks in these series are likely source rocks. Therefore, the elemental geochemistry of the Brahmaputra–Jamuna River sediments is controlled mostly by mechanical breakdown of lithic fragments and subsequent preferential attrition of muscovite > albite > quartz.     

Geomorphometric feature analysis using morphometric parameterization and artificial neural networks

This paper presents a semi-automatic method using an unsupervised neural network to analyze geomorphometric features as landform elements. The Shuttle Radar Topography Mission (SRTM) provided detailed digital elevation models (DEMs) for all land masses between 60°N and 57°S. Exploiting these data for recognition and extraction of geomorphometric features is a challenging task. Results obtained with two methods, Wood's morphometric parameterization and the Self Organizing Map (SOM), are presented in this paper.Four morphometric parameters (slope, minimum curvature, maximum curvature and cross-sectional curvature) were derived by fitting a bivariate quadratic surface with a window size of 5 by 5 to the SRTM DEM. These parameters were then used as input to the two methods. Wood's morphometric parameterization provides point-based features (peak, pit and pass), line-based features (channel and ridge) and area-based features (planar). Since point-based features are defined as having a very small slope when their neighbors are considered, two tolerance values (slope tolerance and curvature tolerance) are introduced. Selection of suitable values for the tolerance parameters is crucial for obtaining useful results.The SOM as an unsupervised neural network algorithm is employed for the classification of the same morphometric parameters into ten classes characterized by morphometric position (crest, channel, ridge and plan area) subdivided by slope ranges. These terrain features are generic landform element and can be used to improve mapping and modeling of soils, vegetation, and land use, as well as ecological, hydrological and geomorphological features. These landform elements are the smallest homogeneous divisions of the land surface at the given resolution. The result showed that the SOM is an efficient scalable tool for analyzing geomorphometric features as meaningful landform elements, and uses the full potential of morphometric characteristics.     

Fault Wear by Damage Evolution During Steady-State Slip

Slip along faults generates wear products such as gouge layers and cataclasite zones that range in thickness from sub-millimeter to tens of meters. The properties of these zones apparently control fault strength and slip stability. Here we present a new model of wear in a three-body configuration that utilizes the damage rheology approach and considers the process as a microfracturing or damage front propagating from the gouge zone into the solid rock. The derivations for steady-state conditions lead to a scaling relation for the damage front velocity considered as the wear-rate. The model predicts that the wear-rate is a function of the shear-stress and may vanish when the shear-stress drops below the microfracturing strength of the fault host rock. The simulated results successfully fit the measured friction and wear during shear experiments along faults made of carbonate and tonalite. The model is also valid for relatively large confining pressures, small damage-induced change of the bulk modulus and significant degradation of the shear modulus, which are assumed for seismogenic zones of earthquake faults. The presented formulation indicates that wear dynamics in brittle materials in general and in natural faults in particular can be understood by the concept of a “propagating damage front” and the evolution of a third-body layer.     

Early formation of K-feldspar in shallow-marine sediments at near-surface temperatures (southern Israel): evidence from K-Ar dating

Authigenic K‐feldspar was investigated in two Albian to Turonian sections in Israel using K‐Ar and Ar‐Ar dating, X‐ray diffraction, scanning electron microscopy and chemical analysis. Both sections comprise a similar succession of shallow‐marine limestones, dolomites and marls, with some sandstone and shale beds of continental origin. The HCl‐insoluble residue fraction of the studied samples consists of clays, quartz, feldspars, goethite and trace amounts of heavy minerals. Most of the insoluble residues have a relatively high K‐feldspar content that has an adularia habit and is concentrated in the 4–7 µm size fraction. The authigenic origin of the K‐feldspar in the fine silt fraction is indicated by its high content relative to quartz, the uniform and idiomorphic shape of the crystals and its limited size range. Of the fine silt (4–7 or 4–10 µm) separates, 40% have ages that are similar to stratigraphic ages within the analytical and biostratigraphic errors. Ar‐Ar dating of a fine silt fraction with 94% K‐feldspar (4–10 µm, sample GYP 7) yields a plateau age identical to the total gas age and similar to the stratigraphic age. These results indicate that the K‐Ar age is not a mixture between detrital and late diagenetic K‐feldspar ages, but is rather an age of formation within a few million years after deposition. It is suggested that the early formation of the K‐feldspar was associated with dolomitization and was induced by residual brines as part of a reflux process.     

Analytical seismic fragility functions for highway and railway embankments and cuts

A fundamental tool in seismic risk assessment of transportation systems is the fragility curve, which describes the probability that a structure will reach or exceed a certain damage state for a given ground motion intensity. Fragility curves are usually represented by two‐parameter (median and log‐standard deviation) cumulative lognormal distributions. In this paper, a numerical approach, in the spirit of the IDA, is applied for the development of fragility curves for highways and railways on embankments and in cuts due to seismic shaking. The response of the geo‐construction to increasing levels of seismic intensity is evaluated using a 2D nonlinear finite element model, with an elasto‐plastic criterion to simulate the soil behavior. A calibration procedure is followed in order to account for the dependency of both the stiffness and the damping to the soil strain level. The effect of soil conditions and ground motion characteristics on the response of the embankment and cut is taken into account considering different typical soil profiles and seismic input motions. This study will provide input for the assessment of the vulnerability of the road/railway network regarding the performance of the embankments and cuts; therefore, the level of damage is described in terms of the permanent ground displacement in these structures. The fragility curves are estimated based on the evolution of damage with increasing earthquake intensity, which is described by PGA. The proposed approach allows the evaluation of new fragility curves considering the distinctive features of the element's geometry, the input motion, and the soil properties as well as the associated uncertainties. A relationship between the computed permanent ground displacement on the surface of the embankment and the PGA in the free field is also suggested based on the results of the numerical analyses. Finally, the proposed fragility curves are compared with existing empirical data and the limitations of their applicability are outlined. Copyright © 2015 John Wiley & Sons, Ltd.