Stratigraphy, Chronology, and Paleoenvironmental Reconstruction of the Quaternary Sedimentary Infilling of a Volcanic Tube in Fuerteventura, Canary Islands

La Cueva del Llano is a volcanic tube of Pleistocene age on Fuerteventura Island, in the Canary Islands. Part of it is infilled with sediments of external origin. These deposits are exceptional in stratigraphic complexity and thickness compared with other known tube infillings, and they comprise nine stratigraphic units deposited in five phases. In Phase I, which has not been dated, sedimentation of cinder from a nearby cone occurred. Phase II began ca. 16,830 ± 900 ¹⁴C yr B.P., whereas phase IV dates to 9280 ± 370 ¹⁴C yr B.P. The interpretation of sedimentary features shows that phases III and V correspond to a dry climate, similar to the present one, whereas the climate was much wetter during phases II and IV. This paleoclimatic sequence agrees with those suggested by the study of deposits formed in other sedimentary environments, not only in Fuerteventura but on other islands of the Canary group and the Sud-Maroc region.     

Stream channel erosion in a rapidly urbanizing region of the US–Mexico border: documenting the importance of channel hardpoints with Structure‐from‐Motion photogrammetry

Urbanization can lead to accelerated stream channel erosion, especially in areas experiencing rapid population growth, unregulated urban development on erodible soils, and variable enforcement of environmental regulations. A combination of field surveys and Structure‐from‐Motion (SfM) photogrammetry techniques was used to document spatial patterns in stream channel geometry in a rapidly urbanizing watershed, Los Laureles Canyon (LLCW), in Tijuana, Mexico. Ground‐based SfM photogrammetry was used to map channel dimensions with 1 to 2 cm vertical mean error for four stream reaches (100–300 m long) that were highly variable and difficult to survey with a differential GPS. Regional channel geometry curves for LLCW had statistically larger slopes and intercepts compared with regional curves developed for comparable, undisturbed reference channels. Cross‐sectional areas of channels downstream of hardpoints, such as concrete reaches or culverts, were up to 64 times greater than reference channels, with enlargement persisting, in some cases, up to 230 m downstream. Percentage impervious cover was not a good predictor of channel enlargement. Proximity to upstream hardpoint, and lack of riparian and bank vegetation paired with highly erodible bed and bank materials may account for the instability of the highly enlarged and unstable cross‐sections. Channel erosion due to urbanization accounts for approximately 25–40% of the total sediment budget for the watershed, and channel erosion downstream of hardpoints accounts for one‐third of all channel erosion. Channels downstream of hardpoints should be stabilized to prevent increased inputs of sediment to the Tijuana Estuary and local hazards near the structures, especially in areas with urban settlements near the stream channel. Copyright © 2017 John Wiley & Sons, Ltd.     

Monitoring of landslide displacements using UAS and control methods based on lines

This study describes a new methodology for monitoring landslide displacements using a set of linear elements included in the terrain. These linear elements are digitized using the products obtained from several photogrammetric flights implemented by means of unmanned aircraft systems in several dates. The control of the displacements between dates is carried out using some new metrics and methods based on lines. The results of the control of the lines are used to analyse the general and particular behaviour of the landslide. Using this type of elements allows us to study some singular behaviour of linear elements included in the landslides (e.g. an affected road can react as a block). The methodology has been tested with success using a real case of an active slope with several landslides which was studied on three separate dates. The results have demonstrated the viability of using this methodology for studying the evolution of the landslides and their consequences regarding certain elements included in the terrain.     

Evaluating proxies for estimating subaerial beach volume change across increasing time scales and various morphologies

Proxies, such as changes in beach profiles and shoreline positions, are commonly used in management and research for estimating changes in subaerial beach volume; however, the accuracy of these proxies across increasing time scales and complex morphologies is unclear. Volume changes associated with along‐beach morphologic variability may not be captured well by changes in profiles, while volume changes associated with across‐beach morphologic variability may not be captured well by measuring shoreline change. This study assesses the impacts of morphologic variations, associated with beach cusps and nourishment material, on volume change estimates from profiles and shoreline change at 0.5 to 3.5 year time periods. Results indicate that profiles spaced ≥ 150 m apart and the shoreline‐change proxy will likely estimate volume change inaccurately over periods ≤ 1 year at beaches that are consistently eroding or accreting and contain cusps. However, over longer time periods (1–3.5 years), estimates of volume change from both proxies improved at those types of beaches. Volume changes at the edges of nourishment areas are not captured well by profiles. When the nourishment material is graded to a ramped morphology, which minimizes across‐beach morphologic variability, the shoreline‐change proxy does accurately estimate volume changes. Both proxies estimate volume changes inaccurately at beaches where volume changes oscillate between erosion and accretion on both short and long time scales because the magnitude of small‐scale changes in volume from the formation and erosion of morphologic features, such as cusps and berms, will always be similar to the longer‐term net volume change. This study suggests that decadal records of shoreline change, which are commonly developed using aerial photography, can be used to help identify the best proxy for estimating volume change; however, recent anthropogenic modifications that impact patterns of beach sedimentation, including nourishment, terminal groins, and inlet‐channel dredging, makes decadal records less useful. Copyright © 2013 John Wiley & Sons, Ltd.     

Comparative study of fuzzy evidential reasoning and fuzzy rule-based approaches: an illustration for water quality assessment in distribution networks

This paper presents the use of two multi-criteria decision-making (MCDM) frameworks based on hierarchical fuzzy inference engines for the purpose of assessing drinking water quality in distribution networks. Incommensurable and uncertain water quality parameters (WQPs) at various sampling locations of the water distribution network (WDN) are monitored. Two classes of WQPs including microbial and physicochemical parameters are considered. Partial, incomplete and subjective information on WQPs introduce uncertainty to the water quality assessment process. Likewise, conflicting WQPs result in a partially reliable assessment of the quality associated with drinking water. The proposed methodology is based on two hierarchical inference engines tuned using historical data on WQPs in the WDN and expert knowledge. Each inference engine acts as a decision-making agent specialized in assessing one aspect of quality associated with drinking water. The MCDM frameworks were developed to assess the microbial and physicochemical aspects of water quality assessment. The MCDM frameworks are based on either fuzzy evidential or fuzzy rule-based inference. Both frameworks can interpret and communicate the relative quality associated with drinking water, while the second is superior in capturing the nonlinear relationships between the WQPs and estimated water quality. More comprehensive rules will have to be generated prior to reliable water quality assessment in real-case situations. The examples presented here serve to demonstrate the proposed frameworks. Both frameworks were tested through historical data available for a WDN, and a comparison was made based on their performance in assessing levels of water quality at various sampling locations of the network.     

Fluoride Biomonitoring around a Large Aluminium Smelter Using Foliage from Different Tree Species

In order to study the pollution gradient in the vicinity of a large aluminium production facility in Patagonia (Argentina), a passive biomonitoring was performed employing foliage from three tree species. Primary scope was to identify pollution gradients and to select suitable tree species which can be used as biomonitor plants in the study area. Therefore, leaves of Eucalyptus rostrata, Populus hybridus and different needle ages of Pinus radiata were collected at different distances from the industry and the fluoride concentration was analysed in washed and unwashed samples in order to determine the amount of external fluoride. Washing reduced the F‐concentrations by 24, 39 and 51% on average in E. rostrata, P. hybridus and P. radiata, respectively, indicating that species‐specific characteristics determine the accumulation and wash‐off of dust‐associated fluorine. F‐concentrations varied from 6 to 3652 ppm F in unwashed samples indicating a steep pollution gradient in the study area. The influence of F‐emissions was discernible in all samples up to a distance of 3500 m from the smelter. E. rostrata accumulated more fluorine than the other species at equal distance from the emission source. The present study confirms that aluminium smelting results in high F deposition in the study area. Establishing a biomonitor network around large emitters is suitable and feasible to evaluate the efficiency of air control measures.     

Land use and topography as predictors of nutrient levels in a tropical catchment

The influence of landscape on nutrient concentration and yield was analyzed in a tropical catchment, the Guare River in northern Venezuela. Spatial and temporal variation in nitrate, SRP and total P were determined in 15 sites located along the river mainstem and tributaries. Higher nitrate concentrations and yields were reported from upper sites and both decreased in the downstream direction along the river mainstem. These trends appear to be related to more pronounced slopes and larger proportions of agricultural and forest lands in subcatchments located in the upper part of the basin, and dense algal mats in the lower reaches. Nitrate values were higher during periods of high discharge, suggesting that nitrate is primarily transported by shallow subsurface flow. SRP represented between 60 and 80% of total P. Phosphorus concentrations were homogeneous along the river mainstem and showed little seasonal variation, while yields were higher in the upper basin. Multiple regression identified slope, runoff and agriculture as primary predictors of nitrate and phosphorus across the watershed, which suggests that both natural and anthropogenic landscape characteristics have a strong influence on nutrient levels in the Guare catchment.     

Social change and land tenure regimes in Mexico

This paper argues that the changing land tenure legislation in Mexico is a concrete reflection of generalized societal attitudes towards indigenous and traditional peasants. It contends that the 1992 neoliberal land-reform mimics the progress-oriented liberal project of the ninettenth century and continues a market-centered modernization process underway since the 1940s, which has been legitimized by an overt institutional disdain and discrimination against indigenous people, peasants and their ways of life. It concludes that this process of assimilation or eradication of traditional agro-ecosystems, cultural diversity and social organization will further increase the vulnerability of Mexican peasants to economic and cultural change. As peasants engage in market-controlled business ventures in the rural areas, migrate to cities, rent or sell their lands, they simultaneously adapt to new values and envision new strategies for subsistence that are increasingly mediated by political-economic forces largely beyond their sphere of influence.     

An Effective Approach to Rehabilitate Damaged Barrier System Against Piping and Contaminant Flow

The monitoring operation of an older impoundment (such as dams and waste barrier materials) during the service life of the structure cannot be overemphasized. Since older infrastructures seem to be more susceptible to piping and seepage failure, their construction design should be analyzed and monitored at places where a potential problem could occur. Once an impoundment is constructed without adequate filters layers and foundation treatments, then the prevention of piping or seepage may require an effective approach to constructing a cut-off wall to prevent eventual failure. In order to identify and understand theses failure modes, it is important to identify the physical parameters of the impoundment system, such as the zones of various soil gradations, the compaction of these zones, the hydraulic conductivity, the compatibility of the soil formations within and beneath the core or liner, as well as the cohesive and dispersive properties of soils at various location within the structure. Once these parameters are known and quantified, an adequate assessment of the structure’s susceptibility to piping or contaminant transport can be established. This type of an analysis will enable the proper design of a cut-off wall and predetermine the effectiveness of its long-term performance. The Vermont Waterbury Dam (built in 1938) is example of seepage related problem that implemented a cut-off wall design to prevent piping paths from undermining the structure. In this case, some forensic sampling had to be performed and the parameters of the soils as just mentioned were key factors in determining the wall design. In this paper, the Waterbury dam rehabilitation is investigated as case studies, in order to better understand how older designs and poor construction of impoundments can lead to piping condition in dams as well as failures in waste barrier systems. The Secant Cut-off wall (constructed at Waterbury Dam) is mentioned as a corrective measure taken for this dam and there is a brief discussion as to how this construction rehabilitation technique can be applied to waste barrier impoundments.