A paleo‐hydro‐geomorphological perspective on urban flood risk assessment

Comprehensive flood risk assessment requires enhanced understanding of the coevolution of the river and its floodplain occupation. Paleoflood analysis to determine flood prone areas in combination with numerical simulations to estimate flood hazard and a historical analysis of urban development to consider the evolution of exposure to floods is a possible way forward. The well‐documented 2006 extreme flood in the Biobío River system and the impacted metropolitan area of Concepción, Chile (~1 million inhabitants) was used as a complex scenario to test the reliability of the proposed method. Results showed that flood prone areas determined with hydro‐geomorphological methods are consistent with those computed with numerical models based on detailed digital elevation models. The flood generation via superficial flow pathways resulting in inundated areas could explain that rivers tend to reactivate paleochannels in extreme conditions. Urban development progressively increased the city's exposure to floods from 0 ha in 1,751 to 1,363 ha in 2006 evidencing a lack of appropriate flood risk management. The 100‐year peak discharge resulted in a high flood risk for about 5% of the total urbanized area of Concepción, and higher discharges are likely to reactivate a paleochannel that crosses the current city centre. We conclude that the proposed paleo hydro‐geomorphology, hydraulic, and urban planning multimethod approach is a necessary tool to enhance understanding of flood risk in complex scenarios to improve flood risk management.     

An upwelling filament off southwest Iberia: Effect on the chlorophyll a and nutrient export

The present paper describes the chemical and biological characteristics of an upwelling filament off southern Iberia in October 2004, based on a total of 42 CTD casts, along with ADCP velocity measurements distributed by an almost regular grid of 15 km mean spacing. Stations were sampled from the surface to a maximum depth of 400 dbar, for nutrients (nitrate, phosphate and silicate) and chlorophyll a determination. The effect of cross-shelf exchange of nutrients and chlorophyll a between the coastal and oceanic waters was also investigated. Data revealed that, during the cruise conducted under relaxed winds, a relatively small filament was formed down to 75 m. However, an amount of 180 t of chlorophyll a was estimated there accompanied by low nutrient concentrations. The observed water properties reveal that SW Iberia is similar to NW Iberia, showing the continuity of the Canary Upwelling System along the Iberian Peninsula, one of poorest upwelling systems of the oceanic eastern boundaries. Nevertheless, the amounts of chlorophyll and nutrients transported through the filament are significant, revealing that those play a key role in the seaward export of matter with an important impact on the regional oceanography of this region. Considering the periods of strong upwelling events and the extent of their duration along the year, the amounts of exported matter must be hugely increased and responsible for the high productivity of these waters.     

Using three different approaches of OSL for the study of young fluvial sediments at the coastal plain of the Usumacinta–Grijalva River Basin,southern Mexico

We use three different approaches of optically stimulated luminescence (OSL) to study young fluvial sediments located at the main channels of one of the largest fluvial systems of North America: the Usumacinta–Grijalva. We use the pulsed photo‐stimulated luminescence (PPSL) system also known as portable OSL reader, full OSL dating and profiling OSL dating in samples extracted from vertical sediment profiles (n = 9) of riverbanks to detect changes in depositional rates of sediments and to obtain the age of the deposits. The results of the PPSL system show that the luminescence signals of vertical sediment profiles highly scattered from the top to the bottom contrast with the luminescence pattern observed on well‐reset sequences of fluvial deposits where luminescence increase from the top to the bottom of the profile. The profiling and full OSL ages yielded large uncertainty values on their ages. Based on the inconsistencies observed in both ages and luminescence patterns of profiles we suggest that these fluvial deposits were not fully reset during their transport. As an explanation, we propose that in the Usumacinta and Grijalva rivers the cyclonic storms during the wet season promote the entrainment of large volumes of sediments due to high‐erosional episodes around the basin resulting from hyper‐concentrated and turbid flows. We conclude that the PPSL, profiling and full OSL dating of sediments are useful tools to quantify and to assess the depositional patterns in fluvial settings during the Holocene. These techniques also can yield information about sites where increases in the sediment load of rivers may produce poorly resetting of grains affecting the results of OSL dating. Copyright © 2015 John Wiley & Sons, Ltd.     

Relevant effects of vegetal cover and litter on the soil hydrological response of two contrasting Mediterranean hillslopes at the end of the dry season (south of Spain)

In Mediterranean regions, hillslopes are generally considered to be a mosaic of sink and source areas that control runoff generation and water erosion processes. These hillslopes used to be characterized by a complex hydrological and erosive response combining Hortonian and saturation excess overland flows. The hydrological response of soils is highly dependent on the soil surface components (e.g. vegetation patches, bare soil, rock fragment cover, crusts), which each one of them is dominated by a certain hydrological process. One of these soil surface components, not widely considered in studies of soil hydrology under Mediterranean conditions, is the accumulation of litter beneath shrubs enhancing water repellency in soils. This study investigates the influence of soil surface components, especially the litter accumulated beneath Cistus spp., in the hydrological and erosive responses of soils on two Mediterranean hillslopes having different exposures. The study was performed by means of rainfall simulation experiments and the Water Drop Penetration Time for measuring water repellency of soils, both techniques being carried out at the end of summer (September 2010) with very dry soils. The results indicate that (i) soil surface components from the north facing hillslope are characterized by a more uniform hydrological and erosive response than those from the south‐facing ones; (ii) the water repellency is more influential on the hydrological response of the north‐facing hillslope due to a greater accumulation of organic rest on the soils as the vegetation cover is also higher; (iii) the south‐facing hillslope seemed to follow the fertility island theory with very degraded bare soil areas, which are the most generated areas of runoff and mobilized sediments; (iv) the experimental area can be considered as a threshold area between the semiarid and subhumid Mediterranean environments, with the south‐facing hillslope being comparable with the former and the north facing one with the latter. Copyright © 2011 John Wiley & Sons, Ltd.     

Geochemical and mineralogical characterization of surficial sediments from the Northern Rias: Implications for sediment provenance and impact of the source rocks

A multidisciplinary study of the elemental geochemistry and mineralogical characteristics of the marine surficial sediment in the Northern Rias (NW Iberian Peninsula) has been carried out. The linkages between the marine sediment composition and their potential sources were examined.The influence of the river-borne sediments is only detected in the innermost part of the three Rias. Regional variations of the mineral assemblages are governed by the source-rock composition of the different geological complexes and the relative source-rock contribution controlled by the continental hydrology. Mineralogical composition of the Ortigueira Ria and adjacent shelf surficial sediments are mainly made up of mafic and ultramafic rocks of the Cape Ortegal complex indicated by the high content of Mg, Mn and chrysotile and riebeckite minerals. In areas nearby Ortegal complex the imprint of heavy minerals present in the surrounding rocks has also been recorded. Barqueiro and Viveiro Rias bed-sediments are influenced by granitic and metamorphic rocks from the Ollo de Sapo complex as revealed by the high contribution of muscovite and quartz.Mining activities in the continental domain left strong imprints on marine surficial sediments. Pyrite content is high in the innermost areas of the Ortigueira Ria since this mineral is exploited in the Mera River basin, whereas high muscovite percentages characterize the Viveiro Ria owing to the abundance of granitic rocks and its exploitation in the Landro River basin. Quartz content is high nearby Cape Estaca de Bares, induced by the presence of an important excavation of this material.     

Geochemical Assessment of a Subtropical Reservoir: A Case Study in Curitiba,Southern Brazil

Suspended particles and dissolved substances in water provide reactive surfaces, influence metabolic activity and contribute to the net sediment deposition. It therefore plays an important part in the ecology and quality of the water mass. The water quality in reservoirs is crucial and it is naturally maintained by flushing and sedimentation, which continuously remove phosphorus from the water. In some reservoirs, however, these removal processes are countered by recycling of ions which could play a key role to start and/or maintain the eutrophic state. The combination of macro‐, trace‐ and microanalysis techniques can be useful to trace pollution sources through a chemical fingerprint, whether be during an acute environmental disaster or a long‐term release of pollutants. The water quality and total metal content of reservoir sediments were assessed in a reservoir, situated in the capital of the Paraná State, in the South‐Eastern part of Brazil. The goal of this paper was to determine the metal presence in the sediment and metal and ionic speciation in the Green River reservoir water. Water and bed sediment samples, collected from various sites during 2008 and 2009, were investigated using XRF, ICP‐OES, ICP‐MS, XRD and zeta potential measurements. Based on the results, the heavy metal concentration and chemical composition of the suspended matter in the water samples, as well as the sediment's chemical composition will be discussed.     

Monitoring in the Western Pacific region shows evidence of seagrass decline in line with global trends

Seagrass systems of the Western Pacific region are biodiverse habitats, providing vital services to ecosystems and humans over a vast geographic range. SeagrassNet is a worldwide monitoring program that collects data on seagrass habitats, including the ten locations across the Western Pacific reported here where change at various scales was rapidly detected. Three sites remote from human influence were stable. Seagrasses declined largely due to increased nutrient loading (4 sites) and increased sedimentation (3 sites), the two most common stressors of seagrass worldwide. Two sites experienced near-total loss from of excess sedimentation, followed by partial recovery once sedimentation was reduced. Species shifts were observed at every site with recovering sites colonized by pioneer species. Regulation of watersheds is essential if marine protected areas are to preserve seagrass meadows. Seagrasses in the Western Pacific experience stress due to human impacts despite the vastness of the ocean area and low development pressures.     

Star formation in NGC5471

We present a study of the star formation in the giant Hii region NGC5471 in the outskirts of M101. We have performed integrated photometry of the mean emission knots. Stellar population analysis with the code chorizos is compatible with the hypothesis that these regions have at least two different populations. The color–magnitude diagram of the region as derived from Hubble Space Telescope/WPFC2 stellar photometry shows that star formation has been going on for the last 70 Myr.     

The contribution to IHY from the COST296 Action MIERS: Mitigation of Ionospheric Effects on Radio Systems

The objective of the COST296 Action MIERS (Mitigation of Ionospheric Effects on Radio Systems) is to develop an increased knowledge of the effects imposed by the ionosphere on practical radio systems, and for the development and implementation of techniques to mitigate the deleterious effects of the ionosphere on such systems (http://www.cost296.rl.ac.uk). The COST296 Community contributes to the international efforts of IHY with scientific and outreach activities as well. After the realization of a web site hosted by Istituto Nazionale di Geofisica e Vulcanologia (INGV), developed also to promote the ionospheric physics to the open public, the COST296 Community supported an initiative addressed to the pupils of the primary school of several European Countries: the realization of a school-calendar dedicated to the Sun and to the Sun-Earth connections.