Vegetation recruitment in an enhanced floodplain: Ancillary benefits of salmonid habitat enhancement

Widespread loss and degradation of riverine habitats due to dams, diversions, levees, and human development have led to an increase in river habitat enhancement projects in recent decades. These projects typically focus on improving either terrestrial (e.g., riparian vegetation) or aquatic (e.g., fish spawning and rearing) habitats, and do not commonly address the relationship between the two systems. However, there is abundant evidence that fundamental linkages exist between terrestrial and aquatic ecosystems, and anthropogenic impacts such as urban expansion, agricultural activities, and river impoundment can synergistically degrade both systems. This study examines the effects of adult and juvenile salmonid habitat restoration on recruitment, density, and composition of riparian vegetation in an area heavily impacted by mining and flow regulation. For a year following in-channel coarse sediment placement and floodplain construction in an area previously covered with coarse mine tailings, we compared the abundance, richness and diversity of vegetation across four treatments: the newly constructed floodplain, isolated mine tailings, mine tailings near an access road, and a remnant riparian area that was less impacted by mining. Richness and diversity were higher in the floodplain than in any of the other treatments; we identified a total of 15 plant families in the floodplain treatments, as compared to three to five families in the other treatments. We observed significant differences in plant assemblage composition between treatments, with higher richness of primarily obligate or facultative wetland plant taxa in the floodplain treatment. This study demonstrates that restoring hydrological linkages between aquatic and terrestrial habitats, and redistribution of sediment size classes altered by mining, can create conditions that promote rapid wetland plant colonization, enhancing biodiversity and improving ecosystem function.     

Macro- and meiofaunal recolonisation of dredged material used for habitat enhancement: temporal patterns in community development

In recent years, dredged material has become regarded as a potential resource and used to create and/or improve intertidal habitats (i.e., beneficial use). This paper presents the results of a sampling programme to investigate the long-term (42 months post-recharge) macro- and meiofaunal recolonisation processes of a beneficial use scheme in south-east England. While univariate indices of community structure indicated that the scheme’s meiofaunal community was never significantly different from that of a nearby reference area, such attributes for macrofauna were continually significantly below those of the reference area, although this was not the case for all reference stations. Multivariate analyses revealed that macro- and meiofaunal community structures were always significantly different from those of the reference communities. We discuss the factors responsible for these observations and propose that assessing recovery of a beneficial use scheme should be undertaken using pre-defined criteria in addition to comparisons with a reference site.     

基于尺度空间技术的归一化Facet模型位场边界识别

边界识别是位场数据处理解释中的重要环节,传统边界识别方法通常不能均衡深、浅部地质体边界.基于尺度空间技术和归一化的Facet模型检测算子,本文开发了一种带通空间滤波和边缘检测相结合的边界识别方法,有效地提高位场数据边界识别的精度和可靠性.为了验证本文算法的有效性和稳定性,分析了不同尺度空间函数和检测算子对算法的影响,并且对比了传统边界识别方法的效果.理论模拟和实际数据分析表明,利用位场垂向二阶导数进行的基于尺度空间技术的归一化Facet模型边界识别方法不仅算法的稳定性强,而且可以避免高阶导数对噪声干扰放大作用,同时均衡深部和浅部地质体边界,从而可以更精确地识别地质体的形态.

     

Evaluating soil moisture estimation from ground-penetrating radar hyperbola fitting with respect to a systematic time-domain reflectometry data collection in a boreal podzolic agricultural field

The upper 30 cm of the soil profile, which hosts the majority of the root biomass, can be considered as the shallow agricultural root zone of most temperate crops. The electromagnetic wave velocity in the soil obtained from reflection hyperbolas in ground-penetrating radar (GPR) data can be used to estimate soil moisture (SM). Finding shallow hyperbolas in a radargram and minimizing the subjective error associated with the hyperbola fitting are the main challenges in this approach. Nevertheless, we were motivated by the recent improvements of hyperbola fitting algorithms, which can reduce the subjective error and processing time. To overcome the difficulty of finding very shallow hyperbolas, we applied the hyperbola fitting method to reflections ranging from 27- to 50-cm depth using a 500-MHz centre-frequency GPR and compared the estimated moisture with vertically installed, 30-cm-long time-domain reflectometry (TDR) sensors. We also compared TDR and GPR sample areas in a 2-D plane using different GPR survey types and different hyperbola depths. SM measured with TDR and GPR were not significantly different according to Mann–Whitney's test. Our analyses showed that a root mean square error of 0.03 m³ m⁻³ was found between the two methods. In conclusion, the proposed method might be suitable to estimate SM with an acceptable accuracy within the root zone if the soil profile is fairly uniform within the application depth range.     

On board short-time high temperature heat treatment of ballast water: a field trial under operational conditions

A ballast water short-time high temperature heat treatment technique was applied on board a car-carrier during a voyage from Egypt to Belgium. Ballast water from three tanks was subjected for a few seconds to temperatures ranging from 55 degrees C to 80 degrees C. The water was heated using the vessel's heat exchanger steam and a second heat exchanger was used to pre-heat and cool down the water. The treatment was effective at causing mortality of bacteria, phytoplankton and zooplankton. The International Maritime Organization (IMO) standard was not agreed before this study was carried out, but comparing our results gives a broad indication that the IMO standard would have been met in some of the tests for the zooplankton, in all the tests for the phytoplankton; and probably on most occasions for the bacteria. Passing the water through the pump increased the kill rate but increasing the temperature above 55 degrees C did not improve the heat treatment's efficacy.     

Magnetic field disturbance in magnetoactive plasma with a localized electrostatic field

Charged particle motion in magnetoactive plasma with an axially symmetric electrostatic field has been studied. It has been indicated that a difference between drift velocities of electrons and ions leads to a magnetic field disturbance. The equations for stationary magnetic field disturbances stretched along the magnetic field, which can be magnetic ducts for propagation of whistlers, have been obtained. The possibility of formation of such ducts by electrostatic fields from thunderstorm sources, penetrating into the ionosphere, has been estimated.     

The telluric field in a halfspace with a spherical inhomogeneity

Summary An exact solution of the distribution of the intensity of the telluric field in a halfspace with a spherical inhomogeneity has been obtained by solving the Laplace equation in bipolar coordinates. This exact solution is compared with the presently known approximate solution, obtained by the method of images, and the region of their coincidence has been determined. For the image solution theoretical relations have been derived for computing the anomaly of the magnetic field. Craphs depict many of the properties of the telluric and magnetic fields on the surface of the considered halfspace for various parameters of the given problem.Dedicated to 90th Birthday of Professor Frantiek Fiala     

Changes associated with Phragmites australis invasion in plant community and soil properties: A study on three invaded communities in a wetland,Victoria, Australia

Phragmites australis invasion is altering plant communities and therefore, soil properties have been changed significantly. This study compared the diversity among three communities in a wetland to assess the impact of invasion by Phragmites and the associated impact on soil properties. Three diversity indices, species richness (S), evenness (E) and Shanon-Weiner index (H) had significantly higher values in uninvaded plots compared to invaded in all the communities. Invaded plots had the lowest diversity, with H = 0 and Simpson’s index (D) = 1, (i.e. they were monospecific). These results support the idea that a reduction in diversity can be expected in wetlands colonized by Phragmites. Phragmites invasion significantly increased soil moisture, EC, phenolics, organic carbon, dehydrogenase activity and microbial biomass (C, N, P) with reduction of pH and arbuscular mycorrhizae fungi spore density compared with uninvaded zones. In addition, the study of antifungal phytochemistry of Phragmites elucidated the decrease of the competitive abilities of native plant Melaleuca ericifolia by interfering with formation of mycorrhizal associations and biomass. Our results suggest that Phragmites invasion has caused significant ecological alterations in communities by demonstrating a combined effect to plant diversity and soil variables.     

Anchor ice formation in streams: a field study

In northern steep streams anchor ice is commonly observed during winter, and plays a key role when considering in‐stream conditions. The understanding, however, of the nature of anchor ice formation is less understood, in particular, under natural conditions. In the following, observations of anchor ice formation in three stream environments with different physical characteristics are presented. Results demonstrate that anchor ice not only form in riffle areas, but also in shallow and slow running stream sections. No linkage between spatial distribution of anchor ice and calculated dimensionless numbers (Froude and Reynolds number) was found. Furthermore, analyses on growth and density showed that anchor ice may be distinguished by two main types. (1) Type I: Lower density forming on top of substrata. (2) Type II: Higher density forming between the substrata filling interstitial spaces. Distribution of anchor ice Types I and II suggests a relation between intensity of turbulence expressed by the Reynolds number, growth pattern and density. As anchor ice has both physical and biological implications on in‐stream environments, findings from the present study may be of particular interest to cold region freshwater stream management. Copyright © 2009 John Wiley & Sons, Ltd.     

Chironomid diversity in the diets of Ponto-Caspian gobiids in a freshwater habitat: Implications for resource partitioning

Chironomid taxa in the diets of six co-occurring gobiids (Caucasian dwarf goby Knipowitschia caucasica; monkey goby, Neogobius fluviatilis; racer goby, Babka gymnotrachelus; round goby, Neogobius melanostomus; bighead goby, Ponticola kessleri; and western tubenose goby, Proterorhinus semilunaris) were investigated in a freshwater habitat in Ukraine. Overall, 32 chironomid morphotypes were identified, among which the most abundant were Polypedilum convictum, Cricotopus sylvestris, Glyptotendipes spp., and Endochironomus albipennis. The racer and monkey gobies were characterized by the highest diversity of chironomid morphotypes in their diets, while the bighead goby by the lowest diversity. Highest similarities of chironomid assemblages in gut contents were observed among the monkey, racer, and round gobies as well as between the bighead and tubenose gobies, while the lowest similarity was observed between the monkey goby and Caucasian dwarf, tubenose, and bighead gobies. Mean sizes of chironomids in the gut contents of different gobiids varied; Caucasian dwarf and tubenose gobies consumed significantly smaller chironomids. Diversity of chironomid taxa in the diets of gobies depended on the type of each fishes’ habitat. Tubenose and bighead gobies preyed mainly on phytophilous chironomids; the monkey and round gobies preferred bottom-dwelling, burrowing chironomids; while Caucasian dwarf and racer gobies consumed both phytophilous and bottom-dwelling, burrowing taxa.     

Early succession of the macroinvertebrate community in a shallow lake: Response to changes in the habitat condition

In the present study the initial succession of the aquatic macroinvertebrate communities of a newly created shallow lake in a wetland area was monitored during 15 months. Three different types of macroinvertebrate samples (multihabitat, associated to the Phragmites australis stands and associated to the sediment) were collected monthly from May 2004 to July 2005. Additional samples were collected in the reed stand in 2007, when the reed belt had become much taller and thicker. Colonization of the lake was fast, and the colonization sequence was mainly related to the dispersal abilities of the taxa. Habitat-specific changes in the assemblage's structure and composition were registered. The communities associated to the sediment showed a decrease in overall biomass, density and species richness along time. The density of the gastropod Physella acuta and the chironomid species Dicrotendipes pallidicornis, Polypedilum nubifer and Tanytarsus horni decreased significantly, after Chara stands declined; while the chironomid Chironomus riparius became dominant. The epiphytic macroinvertebrate communities associated with the reed stands followed a seasonal pattern, with a warm-period community dominated by the chironomid species Ablabesmyia monilis and Psectrocladius sordidellus-group, and a cold-period community dominated by the chironomid species Cricotopus ornatus and D. pallidicornis.     

Evaluating flash-flood warnings at ungauged locations using post-event surveys: a case study with the AIGA warning system

Abstract

This article presents a comparison between real-time discharges calculated by a flash-flood warning system and post-event flood peak estimates. The studied event occurred on 15 and 16 June 2010 at the Argens catchment located in the south of France. Real-time flood warnings were provided by the AIGA (Adaptation d’Information Géographique pour l’Alerte en Crue) warning system, which is based on a simple distributed hydrological model run at a 1-km² resolution using radar rainfall information. The timing of the warnings (updated every 15 min) was compared to the observed flood impacts. Furthermore, “consolidated” flood peaks estimated by an intensive post-event survey were used to evaluate the AIGA-estimated peak discharges. The results indicated that the AIGA warnings clearly identified the most affected areas. However, the effective lead-time of the event detection was short, especially for fast-response catchments, because the current method does not take into account any rainfall forecast. The flood peak analysis showed a relatively good correspondence between AIGA- and field-estimated peak values, although some differences were due to the rainfall underestimation by the radar and rainfall–runoff model limitations.

Editor Z.W. Kundzewicz; Guest editor R.J. Moore

Citation Javelle, P., Demargne, J., Defrance, D., Pansu, J. and Arnaud, P., 2014. Evaluating flash-flood warnings at ungauged locations using post-event surveys: a case study with the AIGA warning system. Hydrological Sciences Journal, 59 (7), 1390–1402. http://dx.doi.org/10.1080/02626667.2014.923970     

Repeatability enhancement in deep-water permanent seismic installations: a dynamic correction for seawater velocity variations

With the increasing use of permanently installed seismic installations, many of the issues in time‐lapse seismic caused by the lack of repeatability can be reduced. However, a number of parameters still influence the degree of reliability of 4D seismic data. In this paper, the specific impact of seawater velocity variations on time‐lapse repeatability is investigated in a synthetic study. A zero‐lag time‐lapse seabed experiment with no change in the subsurface but with velocity changes in the water column is simulated. The velocity model in the water column is constant for the baseline survey while the model for the repeat survey is heterogeneous, designed from sea salinity and temperature measurements in the West of Shetlands. The difference section shows up to 80% of residual amplitude, which highlights the poor repeatability. A new dynamic correction which removes the effect of seawater velocity variations specifically for permanent installations is developed. When applied to the synthetic data, it reduces the difference residual amplitude to about 3%. This technique shows substantial improvement in repeatability beyond conventional time‐lapse cross‐equalization.     

Electric and magnetic field of a direct-current source in a medium with a continuously varying conductivity

Fields due to an electric current source in the atmosphere where the conductivity increases exponentially with altitude have been calculated. Characteristics of the field are described. The current source is assumednot to vary with time.Department of Electronic Engineering, Gumma University.     

Potential field of a stationary electric current in a stratified medium with a three-dimensional perturbing body

Summary The potential of the electric field of a stationary current in a two-layered Earth is calculated by applying Green's formula in the case where a three-dimensional inhomogeneity of different conductivity is located in the basement of the layer. It is proved that the potential outside and inside the perturbing body can be calculated from the potential of an electric double-layer distributed on the surface of this body. An integral equation of the Fredholm type is derived for the surface density of the double-layer, together with some of its integral properties. A similar procedure can be applied to computing the magnetic anomalies of three-dimensional magnetized bodies, geothermal anomalies due to three-dimensional inhomogeneities of different heat conductivity, as well as to potential problems of theoretical electrical engineering.     

A review of pollutants in the sea-surface microlayer (SML): a unique habitat for marine organisms

Boundary layers between different environmental compartments represent critical interfaces for biological, chemical and physical processes. The sea-surface microlayer (uppermost 1-1000 microm layer) forms the boundary layer interface between the atmosphere and ocean. Environmental processes are controlled by the SML, and it is known to play a key role in the global distribution of anthropogenic pollutants. Due to its unique chemical composition, the upper organic film of the SML represents both a sink and a source for a range of pollutants including chlorinated hydrocarbons, organotin compounds, petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAH) and heavy metals. These pollutants can be enriched in the SML by up to 500 times relative to concentrations occurring in the underlying bulk water column. The SML is also a unique ecosystem, serving as an important habitat for fish eggs and larvae. Concentration ranges and enrichment factors of pollutants in the SML in different areas of the world's oceans have been critically reviewed, together with available toxicity data for marine biota found within the SML. Overall, the SML is highly contaminated in many urban and industrialized areas of the world, resulting in severe ecotoxicological impacts. Such impacts may lead to drastic effects on the marine food web and to fishery recruitment in coastal waters. Studies of the toxicity of fish eggs and larvae exposed to the SML contaminants have shown that the SML in polluted areas leads to significantly higher rates of mortality and abnormality of fish embryos and larvae.     

Longitudinal vibration of a slender bar with nonuniform characteristics in presence of a magnetic field

Summary In the present article the magnetic influence on the free vibrations of a slender bar with characteristics slightly different from those of a uniform one has been discussed. It presents a simple approximate solution to this problem. Moreover the frequency equation has been derived.     

Evaluating infiltration losses in a Mediterranean wetland: Las Tablas de Daimiel National Park,Spain

Las Tablas de Daimiel National Park is a series of wetlands which naturally originated from groundwater discharges from the Mancha Occidental aquifer, Spain. Despite the relatively large size of this aquifer, 30 years of intensive groundwater pumping have significantly depleted the water table. As a result, wetlands only remain functional due to artificial inflows. Infiltration loss is therefore a key parameter to evaluate how much water is needed to maintain ecosystem functionality. Although yearly infiltration estimates existed prior to this work, these did not take into account key parameters such as the temporal evolution of the flooded area. This paper presents a more concrete estimate of the average infiltration losses. Infiltration is calculated as the closure term of daily water balances during a period of time where all other elements were known to an acceptable accuracy. A validation mechanism is provided to check the potential utility of the calculated infiltration in wetland management practices. Copyright © 2008 John Wiley & Sons, Ltd.     

Circulation in a Southern Italy coastal basin: Modelling and field measurements

The purpose of the present work is to study the hydrodynamic aspects in the Mar Piccolo, a coastal basin located on the northern side of the Gulf of Taranto in the Ionian Sea (Italy), by means of mathematical modelling and field measurements. The latter were assessed during three surveys carried out in the spring–summer of 2002. Collected data have been utilized as input by the 3-D Princeton Ocean Model, which is a sigma coordinate, free surface ocean model which was developed in the late 1970s by Blumberg and Mellor. Simulations in baroclinic condition were forced by a homogeneous and stationary wind field, a simple tidal wave, a constant outflow and vertical stratification of temperature and salinity. A comparison was made between the mathematical modelling results and the field measurements collected during the surveys, in terms of velocity. It was observed that during small tides, when the wind effect prevails over the stratification effect, the best model results were obtained for the most superficial layer and that superficial patterns reproduced by the model are more sensitive to wind direction than to stratification. On the contrary, when the wind effect decreases or the thermohaline effect rises, best results occurred in deeper layers.