Bank failure and erosion on the Ohio river

River bank erosion has benn the focus of recent concern surrounding construction and operation of navigation dams along the Ohio River. Such factors as navigation pool levels, pool fluctuations, and towboat traffic have been alleged to be the cause of severe erosion of Ohio River banks. In this paper available information on Ohio River bank erosion is examined from an historical perspective and from the perspective of recent comprehensive investigations. Historical illustrations, photographs, and published reports indicate a history of significant bank erosion for more than 150 years on the Ohio River. Results of field bank condition reconnaissance studies suggest that construction of navigation dams on the Ohio River has not significantly accelerated or intensified bank erosion. Analysis of erosional mechanisms indicates that bank failure and erosion on the Ohio River are complex and episodic phenomena; however, the principal erosional mechanisms appear to be bank material removal by current tractive forces during flood events and internal erosion of bank materials by bank discharge following floods. It is concluded that waves generated by tow and recreational vessels have little impact on bank stability, but land use changes may affect slope stability and bank erosion.     

Large-Scale and Mesoscale Distribution of Plankton Biomass and Metabolic Activity in the Northeastern Central Atlantic

Plankton biomass and indices of metabolism and growth [electron transport system (ETS), glutamate dehydrogenase (GDH) and aspartate transcarbamylase (ATC) activities] were studied over a 2,800 km east-west section of the tropical North Atlantic Ocean (21°N) in <200, 200–500 and >;500 µm size classes. On the large-scale, zooplankton (>;200 µm) enzymatic activities increased westward in the study section, where large cyanobacteria chains (Trichodesmium spp.) were observed. Parallel to it, an increase in medium calanoids (1–2 mm length) was observed towards the western part of the transect, whereas small calanoids (<1 mm) were dominant throughout the boundary area of the subtropical gyre. Microplankton ETS and mesoplankton ETS and ATC activities seemed to match the wave length of low frequency waves. Our results suggest that such waves are related to the observed enhancement of metabolic activity of micro- and mesoplankton. The large-scale and mesoscale variability observed give evidence of the inadequacy of assuming a steady-state picture of the euphotic zone of tropical and subtropical waters.     

Comparative physical properties of weathered impregnated and unimpregnated marble

Chemical weathering of marbles has greatly increased during the past decades. The gaseous pollutants generated mainly by combustion of automobile, domestic, and industrial fuels have contributed significantly towards this increase. The weathering affects marble gradationally from outside inwards, producing three distinct zones. The success of a technique developed to provide cohesion to reduced and dislodged calcite crystals in the zone of weathering, by impregnation with resins which even permeate the inter-crystalline boundaries in the non-weathered region, is tested. As these weathered layers are quite thin and easily destructible, direct measurement of compressive strength is impossible. This property is, therefore, determined indirectly via Shore scleroscope hardness and specific gravity.

The impregnation increased the strength of the weathered zone up to 59% and of the unweathered region up to 24%. Corresponding values for permeability and capillarity, relative to untreated specimens, change inversely to strength changes as the pores receive relatively larger amounts of resin in the outer weathered region than in the unweathered region in depth. This phenomenon is substantiated by scanning electron microscopy (S.E.M.).     

(Na,Ca)(Ti3+,Mg)Si2O6-clinopyroxenes at high pressure: influence of cation substitution on elastic behavior and phase transition

A compressional study of (Na,Ca)(Ti³⁺,Mg)Si₂O₆-clinopyroxenes was carried out at high pressures between 10⁻⁴ and 10.2 GPa using in situ single-crystal X-ray diffraction, Raman spectroscopy and optical absorption spectroscopy. Compressional discontinuities accompanied by structural changes, in particular, the appearance of two distinct Ti³⁺–Ti³⁺ distances within the octahedral chains at 4.37 GPa, provide evidence for the occurrence of a phase transition in NaTi³⁺Si₂O₆. Equation-of-state parameters are K ₀ = 115.9(7) GPa with K′ = −0.9(3) and K ₀ = 102.7(8) GPa with K′ = 4.08(5) for the low- and high-pressure range, respectively. The transition involves a C2/c–P [`1] \overline{1} symmetry change, which can be confirmed by the occurrence of new modes in Raman spectra. Since no significant discontinuity in the evolution of the unit-cell volume with pressure has been observed, the transition appears to be second-order in character. The influence of the coupled substitution Na⁺Ti³⁺↔Ca²⁺Mg²⁺ on the static compression behavior and the structural stability has been investigated using a sample of the intermediate composition (Na_0.54Ca_0.46)(Mg_0.46Ti_0.54)Si₂O₆. No evidence for a deviation from continuous compression behavior has been found, neither in lattice parameter nor in structural data and the fit of a third-order Birch–Murnaghan equation-of-state to the pressure–volume data yields a bulk modulus of K ₀ = 109.1(5) GPa and K′ = 5.02(13). Raman and polarized absorption spectra have been compared to NaTiSi₂O₆ and reveal major similarities. The main driving force for the phase transition in NaTi³⁺Si₂O₆ is the localization of the Ti³⁺ d-electron and the accompanying distortion, which is suppressed in the (Na,Ca)(Ti³⁺,Mg)Si₂O₆-clinopyroxene.     

A geographic approach for combining social media and authoritative data towards identifying useful information for disaster management

In recent years, social media emerged as a potential resource to improve the management of crisis situations such as disasters triggered by natural hazards. Although there is a growing research body concerned with the analysis of the usage of social media during disasters, most previous work has concentrated on using social media as a stand-alone information source, whereas its combination with other information sources holds a still underexplored potential. This article presents an approach to enhance the identification of relevant messages from social media that relies upon the relations between georeferenced social media messages as Volunteered Geographic Information and geographic features of flood phenomena as derived from authoritative data (sensor data, hydrological data and digital elevation models). We apply this approach to examine the micro-blogging text messages of the Twitter platform (tweets) produced during the River Elbe Flood of June 2013 in Germany. This is performed by means of a statistical analysis aimed at identifying general spatial patterns in the occurrence of flood-related tweets that may be associated with proximity to and severity of flood events. The results show that messages near (up to 10 km) to severely flooded areas have a much higher probability of being related to floods. In this manner, we conclude that the geographic approach proposed here provides a reliable quantitative indicator of the usefulness of messages from social media by leveraging the existing knowledge about natural hazards such as floods, thus being valuable for disaster management in both crisis response and preventive monitoring.     

Caribbean island-arc rifting and back-arc basin development in the Late Cretaceous: Geochemical, isotopic and geochronological evidence from Central Hispaniola

We present new regional petrologic, geochemical, Sr–Nd isotopic, and U–Pb geochronological data on the Turonian–Campanian mafic igneous rocks of Central Hispaniola that provide important clues on the development of the Caribbean island-arc. Central Hispaniola is made up of three main tectonic blocks—Jicomé, Jarabacoa and Bonao—that include four broad geochemical groups of Late Cretaceous mafic igneous rocks: group I, tholeiitic to calc-alkaline basalts and andesites; group II, low-Ti high-Mg andesites and basalts; group III, tholeiitic basalts and gabbros/dolerites; and group IV, tholeiitic to transitional and alkalic basalts. These igneous rocks show significant differences in time and space, from arc-like to non-arc-like characteristics, suggesting that they were derived from different mantle sources. We interpret these groups as the record of Caribbean arc-rifting and back-arc basin development in the Late Cretaceous. The> 90 Ma group I volcanic rocks and associated cumulate complexes preserved in the Jicomé and Jarabacoa blocks represent the Albian to Cenomanian Caribbean island-arc material. The arc rift stage magmatism in these blocks took place during the deposition of the Restauración Formation from the Turonian–Coniacian transition (~ 90 Ma) to Santonian/Lower Campanian, particularly in its lower part with extrusion at 90–88 Ma of group II low-Ti, high-Mg andesites/basalts. During this time or slightly afterwards adakitic rhyolites erupted in the Jarabacoa block. Group III tholeiitic lavas represent the initiation of Coniacian–Lower Campanian back-arc spreading. In the Bonao block, this stage is represented by back-arc basin-like basalts, gabbros and dolerite/diorite dykes intruded into the Loma Caribe peridotite, as well as the Peralvillo Sur Formation basalts, capped by tuffs, shales and Campanian cherts. This dismembered ophiolitic stratigraphy indicates that the Bonao block is a fragment of an ensimatic back-arc basin. In the Jicomé and Jarabacoa blocks, the mainly Campanian group IV basalts of the Peña Blanca, Siete Cabezas and Pelona–Pico Duarte Formation, represent the subsequent stage of back-arc spreading and off-axis non-arc-like magmatism, caused by migration of the arc toward the northeast. These basalts have geochemical affinities with the mantle domain influenced by the Caribbean plume, suggesting that mantle was flowing toward the NE, beneath the extended Caribbean island-arc, in response to rollback of the subducting proto-Caribbean slab.     

Deep alpine valleys: examples of geophysical explorations in Austria

Results from geophysical explorations of three deep valleys, selected from different tectonic regimes in the Eastern Alps (Ötz-, Oichten-, and Drau Valley), are presented and discussed. Ongoing tectonic deformation may use tectonic structures related to these valleys. However, seismic activity is low there. During the Würm ice age, the thickness of the ice cover ranged between 300 and 1,500 m above present ground elevation. The geophysical investigations comprised reflection seismology, gravity- and resistivity surveys. The maximum depth down to the erosional base of the valleys varies from ~340 to 700 m. Distinct layer packages of the valley-infill at depths greater than 250 m were termed “old valley-fill”. Geophysical parameters and a comparison with the reflection seismic image of an intermediate layer at the recent Pasterze glacier suggest that the top of the “old valley-fill” represents the glacier bed during the decay of the Würm glaciation. Deep erosion is not related to high basal shear stress. The confluence of tributary glaciers is apparently not a significant factor for deep erosion in our examples of deep alpine valleys. We conclude that deep erosion may be related to high water pressure at the glacier bed, supported by specific processes of tectonic weakening.     

The influence of systematically incomplete shallow landslide inventories on statistical susceptibility models and suggestions for improvements

Complete landslide inventories are rarely available. The objectives of this study were to (i) elaborate the influence of incomplete landslide inventories on statistical landslide susceptibility models and to (ii) propose suitable modelling strategies that can reduce the effects of inventory-based incompleteness. In this context, we examined whether the application of a novel statistical approach, namely mixed-effects models, enables predictions that are less influenced by such inventory-based errors.The study was conducted for (i) an area located in eastern Austria and (ii) a synthetically generated data set. The applied methodology consisted of a simulation of two different inventory-based biases and an in-depth evaluation of subsequent modelling results. Inventory-based errors were simulated by gradually removing landslide data within forests and selected municipalities. The resulting differently biased inventories were introduced into logistic regression models while we considered the effects of including or excluding predictors that are directly related to the respective inventory-based bias. Mixed-effects logistic regression was used to account for variation that was due to an inventory-based incompleteness.The results show that most erroneous predictions, but highest predictive performances, were obtained from models generated with highly incomplete inventories and predictors that were able to directly describe the respective incompleteness. An exclusion of such bias-describing predictors led to systematically confounded relationships. The application of mixed-effects models proved valuable to produce predictions that were least affected by inventory-based errors.This paper highlights that the degree of inventory-based incompleteness is only one of several aspects that determine how an inventory-based bias may propagate into the final results. We propose a four-step procedure to deal with incomplete inventories in the context of statistical landslide susceptibility modelling.     

Fluorescence and Reflectance for the in-situ Determination of Some Quality Parameters of Surface Waters

Ship-based experiments around Berlin and laboratory tests were carried out in order to develop spectroscopic methods for the in-situ determination of chlorophyll a (Chla) and chemical oxygen demand (COD_cr) of surface waters. The regression analysis of spectroscopic data (reflectance (R); laser-stimulated and conventional fluorescence (I_F)) and chemical-biological data yielded correlations of a relatively good quality.