Browsing by Author "Rivas Casado, Monica"
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Item Open Access Accuracy assessment of surveying strategies for the characterization of microtopographic features that influence surface water flooding(MDPI, 2023-04-02) Ramachandran, Rakhee; Bajón Fernández, Yadira; Truckell, Ian; Constantino, Carlos; Casselden, Richard; Leinster, Paul; Rivas Casado, MonicaWith the increase in rainfall intensity, population, and urbanised areas, surface water flooding (SWF) is an increasing concern impacting properties, businesses, and human lives. Previous studies have shown that microtopography significantly influences flow paths, flow direction, and velocity, impacting flood extent and depth, particularly for the shallow flow associated with urban SWF. This study compares two survey strategies commonly used by flood practitioners, S1 (using Unmanned Aerial Systems-based RGB data) and S2 (using manned aircraft with LiDAR scanners), to develop guidelines on where to use each strategy to better characterise microtopography for a range of flood features. The difference between S1 and S2 in elevation and their accuracies were assessed using both traditional and robust statistical measures. The results showed that the difference in elevation between S1 and S2 varies between 11 cm and 37 cm on different land use and microtopographic flood features. Similarly, the accuracy of S1 ranges between 3 cm and 70 cm, and the accuracy of S2 ranges between 3.8 cm and 30.3 cm on different microtopographic flood features. Thus, this study suggests that the flood features of interest in any given flood study would be key to select the most suitable survey strategy. A decision framework was developed to inform data collection and integration of the two surveying strategies to better characterise microtopographic features. The findings from this study will help improve the microtopographic representation of flood features in flood models and, thus, increase the ability to identify high flood-risk prompt areas accurately. It would also help manage and maintain drainage assets, spatial planning of sustainable drainage systems, and property level flood resilience and insurance to better adapt to the effects of climate change. This study is another step towards standardising flood extent and impact surveying strategies.Item Open Access Acoustic Doppler Current profiler measurements near a weir with fish pass: assessing solutions to compass errors, spatial data referencing and spatial flow heterogeneity(2015-11-18) Kriechbaumer, Thomas; Blackburn, Kim; Everard, Nick; Rivas Casado, MonicaThere has been an increasing interest in the use of Acoustic Doppler Current Profilers (ADCPs) to characterise the hydraulic conditions near river engineering structures such as dams, fish passes and groins, as part of ecological and hydromorphological assessments. However, such ADCP applications can be limited by compass errors, obstructed view to navigation satellites, frequent loss of bottom tracking and spatially heterogeneous flow leading to erroneous water velocity measurements. This study addresses these limitations by (i) developing a heading sensor integration algorithm that corrects compass errors from magnetic interference, (ii) testing a Total Station based technique for spatial ADCP data referencing and (iii) evaluating a recently proposed data processing technique that reduces bias from spatial flow heterogeneity. The integration of these techniques on a radio control ADCP platform is illustrated downstream of a weir with fish pass on the River Severn, UK. The results show that each of the techniques can have a statistically significant effect on the estimated total water velocities and can strongly affect measures of vorticity. The obtained three-dimensional flow maps are suitable to describe the magnitude and orientation of the fish pass attraction flow in relation to competing flows and to highlight areas of increased vorticity.Item Open Access An assessment of the risk to surface water ecosystems of groundwater P in the UK and Ireland(Elsevier , 2010-03-15T00:00:00Z) Holman, Ian P.; Howden, Nicholas J. K.; Bellamy, Patricia H.; Willby, N.; Whelan, Michael J.; Rivas Casado, MonicaA good quantitative understanding of phosphorus (P) delivery is essential in the design of management strategies to prevent eutrophication of terrestrial freshwaters. Most research to date has focussed on surface and near-surface hydrological pathways, under the common assumption that little P leaches to groundwater. Here we present an analysis of national patterns of groundwater phosphate concentrations in England and Wales, Scotland, and the Republic of Ireland, which shows that many groundwater bodies have median P concentrations above ecologically significant thresholds for freshwaters. The potential risk to receptor ecosystems of high observed groundwater P concentrations will depend on (1) whether the observed groundwater P concentrations are above the natural background; (2) the influence of local hydrogeological settings (pathways) on the likelihood of significant P transfers to the receptor; (3) the sensitivity of the receptor to P; and, (4) the relative magnitude of P transfers from groundwater compared to other P sources. Our research suggests that, although there is often a high degree of uncertainty in many of these factors, groundwater has the potential to trigger and/or maintain eutrophication under certain scenarios: the assumption of groundwater contribution to river flows as a ubiquitous source of dilution for P-rich surface runoff must therefore be questioned. Given the regulatory importance of P concentrations in triggering ecological quality thresholds, there is an urgent need for detailed monitoring and research to characterise the extent and magnitude of different groundwater P sources, the likelihood for P transformation and/or storage along aquifer- hyporheic zone flow paths and to identify the subsequent risk to receptor ecosystems. (C) 2009 Elsevier B.V. All rights reserved.Item Open Access Automated identification of river hydromorphological features using UAV high resolution aerial imagery(MDPI, 2015-11-04) Rivas Casado, Monica; Ballesteros Gonzalez, Rocio; Kriechbaumer, Thomas; Veal, Amanda VealEuropean legislation is driving the development of methods for river ecosystem protection in light of concerns over water quality and ecology. Key to their success is the accurate and rapid characterisation of physical features (i.e., hydromorphology) along the river. Image pattern recognition techniques have been successfully used for this purpose. The reliability of the methodology depends on both the quality of the aerial imagery and the pattern recognition technique used. Recent studies have proved the potential of Unmanned Aerial Vehicles (UAVs) to increase the quality of the imagery by capturing high resolution photography. Similarly, Artificial Neural Networks (ANN) have been shown to be a high precision tool for automated recognition of environmental patterns. This paper presents a UAV based framework for the identification of hydromorphological features from high resolution RGB aerial imagery using a novel classification technique based on ANNs. The framework is developed for a 1.4 km river reach along the river Dee in Wales, United Kingdom. For this purpose, a Falcon 8 octocopter was used to gather 2.5 cm resolution imagery. The results show that the accuracy of the framework is above 81%, performing particularly well at recognising vegetation. These results leverage the use of UAVs for environmental policy implementation and demonstrate the potential of ANNs and RGB imagery for high precision river monitoring and river management.Item Open Access Characterisation and control of the biosolids storage environment: Implications for E. coli dynamics(Elsevier, 2020-08-15) Fane, Sarah Elizabeth; Nocker, Andreas; Vale, Peter C. J.; Rivas Casado, Monica; Cartmell, Elise; Harris, Jim A.; Bajón Fernández, Yadira; Tyrrel, Sean F.E. coli survival in biosolids storage may present a risk of non-compliance with guidelines designed to ensure a quality product safe for agricultural use. The storage environment may affect E. coli survival but presently, storage characteristics are not well profiled. Typically biosolids storage environments are not actively controlled or monitored to support increased product quality or improved microbial compliance. This two-phased study aimed to identify the environmental factors that control bacterial concentrations through a long term, controlled monitoring study (phase 1) and a field-scale demonstration trial modifying precursors to bacterial growth (phase 2). Digested and dewatered biosolids were stored in operational-scale stockpiles to elucidate factors controlling E. coli dynamics. E. coli concentrations, stockpile dry solids, temperature, redox and ambient weather data were monitored. Results from ANCOVA analysis showed statistically significant (p < 0.05) E. coli reductions across storage periods with greater die-off in summer months. Stockpile temperature had a statistically significant effect on E. coli survival. A 4.5 Log reduction was measured in summer (maximum temperature 31 °C). In the phase 2 modification trials, covered stockpiles were able to maintain a temperature >25 °C for a 28 day period and achieved a 3.7 Log E. coli reduction. In winter months E. coli suppression was limited with concentrations >6 Log10 CFU g−1 DS maintained. The ANCOVA analysis has identified the significant role that physical environmental factors, such as stockpile temperature, has on E. coli dynamics and the opportunities for controlItem Open Access Combining unmanned aircraft systems and image processing for wastewater treatment plant asset inspection(MDPI, 2020-05-05) Martínez, Jorge Sancho; Bajón Fernández, Yadira; Leinster, Paul; Rivas Casado, MonicaWastewater treatment plants are essential for preserving the water quality of freshwater and marine ecosystems. It is estimated that, in the UK, as much as 11 billion liters of wastewater are treated on a daily basis. Effective and efficient treatment of wastewater requires treatment plants to be maintained in good condition. Recent studies have highlighted the potential of unmanned aircraft systems (UASs) and image processing to be used in autonomous and automated monitoring systems. However, the combined use of UASs and image processing for wastewater treatment plant inspections has not yet been tested. This paper presents a novel image processing-UAS framework for the identification of failures in trickling filters and activated sludge facilities. The results show that the proposed framework has an accuracy of 95% in the detection of failures in activated sludge assets, with the accuracy ranging between 55% and 81% for trickling filters. These results are promising and they highlight the potential use of the technology for the inspection of wastewater treatment plantsItem Open Access Computational fluid dynamics simulations of water flow on a studded upstream eel pass(Wiley, 2021-07-19) Syihab, Abu B. M. Ibnu; Verdin, Patrick G.; Wright, Rosalind M.; Piper, Adam T.; Rivas Casado, MonicaThe European eel population has undergone a significant decline in recruitment over the last 3–4 decades. Anthropogenic riverine barriers that disrupt the eel's life cycle when migrating upstream are contributory factors in this decline. The development of eel passage facilities is one of many attempts to mitigate this problem. In upstream passes, eels rely on a substrate in the base of the pass to assist their ascent by climbing and/or swimming. This study numerically evaluates, using computational fluid dynamics, the hydrodynamic characteristics of water flow on a studded substrate, under a range of installation angles and water flowrates. To assess and predict the efficiency of the pass, simulated flow field data were used to create pass-ability maps by comparing simulated velocity data with eel swimming capabilities. An 11° installation angle with a ramp flowrate of 1.12 × 10−3 m3/s per metre width was shown to be likely most suitable for 70 mm long eels, and could be used by eels with sizes up to 150 mm. The numerical study has also shown that under specific water flowrates, installation angles of 30° or more can make the water level fluctuate and splash out of the eel pass, resulting in potential inefficiency in ramp water supply, while posing additional challenges for eels ascending the pass.Item Open Access Contrasting changes in soil carbon under first rotation, secondary and historic woodland in England and Wales(Elsevier, 2021-12-09) Rivas Casado, Monica; Bellamy, Patricia; Leinster, Paul; Burgess, Paul J.This study investigates changes in soil carbon under woodland combining data from the National Soil Inventory of England and Wales with data from the National Inventory of Woodlands and Trees to create a unique dataset with woodland management information at the sites where soil carbon was measured in 1980 and 2003. Three woodland management stages were compared: first rotation (i.e. recently planted on land not previously under woodland and not yet harvested), second rotation (i.e. harvested at least once), and historic woodlands. Woodlands in their first rotation demonstrated a reduction (p < 0.01) in topsoil organic carbon content typically losing over 2% per year, whereas no change (p ≥ 0.10) was observed for the other two woodland types. This large reduction in organic carbon could not be statistically explained by a higher inherent soil carbon, as the mean soil carbon content of the first rotation and second rotation woodlands were not (p ≥ 0.50) different. The average age of the woodlands under first rotation was 42 years, indicating that the period of significant soil carbon loss could go on for about 40 years after planting.Item Restricted Data relating to "High resolution (cm scale) elevation data of Cockermouth Town, UK"(Cranfield University, 2024-08-07) Mukherjee, Kriti; Rivas Casado, Monica; Ramachandran, Rakhee; Leinster, PaulThe project is focused on 'Harnessing long-term gridded rainfall data and microtopographic insights to characterise risk from surface water flooding'. The data provides the microtopography information of Cockermouth Town in England and the property resilience and resistance information. Three data sets are provided; 1.Elevation model at 25 cm resolution generated from lidar point clouds captured from aircraft; 2. Elevation model at 10 cm resolution generated from stereo photos captured by photographic cameras mounted on UAV; 3. shapefile having attributes related to flood resilience and resistance information for the residential buildings of Cockermouth Town.Item Open Access Data supporting 'Understanding the effects of Digital Elevation Model resolution in urban fluvial flood modelling'(Cranfield University, 2023-02-10 17:21) Muthusamy, Manoranjan; Rivas Casado, Monica; Leinster, Paul; Butler, DavidThis HERAS 2D model setup files and results were produced to study the effect of DEM resolution in fluvial flood modelling using Cockermouth storm Desmend flood (2015). -Link to the publication will be added once available- Note: This folder contains DEM data downloaded from Environment Agency, UK. This metadata record is for Approval for Access product AfA458. Attribution statement: (c) Environment Agency copyright and/or database right 2019. All rights reservedItem Open Access Detection of flood damage in urban residential areas using object-oriented UAV image analysis coupled with tree-based classifiers(MDPI, 2021-10-01) Zawadzka, Joanna Ewa; Truckell, Ian; Khouakhi, Abdou; Rivas Casado, MonicaTimely clearing-up interventions are essential for effective recovery of flood-damaged housing, however, time-consuming door-to-door inspections for insurance purposes need to take place before major repairs can be done to adequately assess the losses caused by flooding. With the increased probability of flooding, there is a heightened need for rapid flood damage assessment methods. High resolution imagery captured by unmanned aerial vehicles (UAVs) offers an opportunity for accelerating the time needed for inspections, either through visual interpretation or automated image classification. In this study, object-oriented image segmentation coupled with tree-based classifiers was implemented on a 10 cm resolution RGB orthoimage, captured over the English town of Cockermouth a week after a flood triggered by storm Desmond, to automatically detect debris associated with damages predominantly to residential housing. Random forests algorithm achieved a good level of overall accuracy of 74%, with debris being correctly classified at the rate of 58%, and performing well for small debris (67%) and skips (64%). The method was successful at depicting brightly-colored debris, however, was prone to misclassifications with brightly-colored vehicles. Consequently, in the current stage, the methodology could be used to facilitate visual interpretation of UAV images. Methods to improve accuracy have been identified and discussed.Item Open Access Development of a UAV based framework for CH4 monitoring in sludge treatment centres(MDPI, 2023-07-25) Hiniduma Gamage, Kavindi; Bajón Fernández, Yadira; Srinamasivayam, Bharanitharan; Turner, Duncan; Rivas Casado, MonicaWith the increasing trend in the global average temperature, the UK’s water industry has committed to achieve Net Zero by 2030 and part of this includes cutting CH4 emissions from sludge treatment facilities. Currently, emissions are estimated following the carbon accounting workbook guidelines and using default emission factors. However, this method might not be a true representation of emissions as these vary depending on many factors. The use of unmanned aerial vehicles (UAVs) has proved cost effective for environmental monitoring tasks requiring high spatial resolution information. Within the context of CH4 emissions and in the last decade, the technology has been curtailed by sensor weight and size. Recent advances in sensor technology have enabled the development of a fit-for purpose UAV CH4 sensor (U10) which uses Tuneable Diode Laser Absorption Spectroscopy. This study intends to develop a framework for CH4 data collection strategies from sludge treatment centres using UAV-U10 technology and asset level CH4 enhancement estimations based on geostatistical interpolation techniques and the mass balance approach. The framework presented here enables the characterization of spatial and temporal variations in CH4 concentrations. It promotes asset level CH4 enhancement estimation based on on-site measurements.Item Open Access Disruption of cells in biosolids affects E. coli dynamics in storage(IWA Publishing, 2019-05-22) Fane, Sarah Elizabeth; Madureira, D.; Nocker, Andreas; Vale, Peter C. J.; Rivas Casado, Monica; Wilson, A.; Bajón Fernández, Yadira; Harris, Jim A.; Cartmell, Elise; Tyrrel, SeanAchieving microbial compliance during biosolids storage can be complicated by the unpredictable increase of Escherichia coli. Thermal treatment during anaerobic digestion (AD) and the effects of dewatering may be a significant factor contributing to indicator survival. Shear forces present during dewatering may promote cell damage, releasing nutrient for E. coli growth. The effect of cell damage on E. coli survival was assessed in laboratory-scale thermal and physical disruption experiments. E. coli growth curves for disrupted treatments were compared with control conditions and quantified using flow cytometry and membrane filtration techniques. A significant difference (p < 0.05) in the level of damaged cells between control and disrupted conditions was observed. For thermal and physical disruption treatments, the peak of E. coli concentration increased significantly by 1.8 Log and 2.4 Log (CFU (colony forming units) g−1 DS), respectively, compared with control treatments. Research findings contribute to the understanding of bacterial growth and death dynamics in biosolidsItem Open Access Exploring the usefulness of a simple linear regression model for understanding price movements of selected recycled materials in UK.(Elsevier Science B.V., Amsterdam., 2012-03-31T00:00:00Z) Angus, Andrew; Rivas Casado, Monica; Fitzsimons, DThe price volatility of recycled materials exposes many different organisations to financial and regulatory risk. These risks can be partially mitigated by improved understanding of price volatility using econometric models, although these have tended to be sophisticated autoregressive models, beyond the analytical capability or cost structure of the average market participant. In this context, this study explores the use of a simple linearregression model to understand the behaviour of prices for recycled plastic, recovered paper and glass, based on the price of their primary inputs, with a specific focus on the UK market. The results of the simple regression model are compared with a wavelet analysis to determine what information is lost in the trade off with simplicity. Both models found significant relationships between the price of crude oil/ethylene/naphtha and recycled plastics and it appears that there is no loss in model performance by using oil as the explanatory variable, rather than direct inputs (ethylene/naphtha). However, few correlations were found for recovered paper and glass. Initial findings from the wavelet analysis suggest that since 2004 the oil price has become more closely linked to the price of recycled plastics. It must be noted that this study is exploratory and particular dynamics of UK markets for recycled materials may affect price development in a way that would not be repeated on international markets.Item Open Access Field-based measurement of hydrodynamics associated with engineered in-channel structures: the example of fish pass assessment(Cranfield University, 2016-03) Kriechbaumer, Thomas; Rivas Casado, Monica; Blackburn, Kim; Gill, Andrew B.The construction of fish passes has been a longstanding measure to improve river ecosystem status by ensuring the passability of weirs, dams and other in- channel structures for migratory fish. Many fish passes have a low biological effectiveness because of unsuitable hydrodynamic conditions hindering fish to rapidly detect the pass entrance. There has been a need for techniques to quantify the hydrodynamics surrounding fish pass entrances in order to identify those passes that require enhancement and to improve the design of new passes. This PhD thesis presents the development of a methodology for the rapid, spatially continuous quantification of near-pass hydrodynamics in the field. The methodology involves moving-vessel Acoustic Doppler Current Profiler (ADCP) measurements in order to quantify the 3-dimensional water velocity distribution around fish pass entrances. The approach presented in this thesis is novel because it integrates a set of techniques to make ADCP data robust against errors associated with the environmental conditions near engineered in-channel structures. These techniques provide solutions to (i) ADCP compass errors from magnetic interference, (ii) bias in water velocity data caused by spatial flow heterogeneity, (iii) the accurate ADCP positioning in locales with constrained line of sight to navigation satellites, and (iv) the accurate and cost-effective sensor deployment following pre-defined sampling strategies. The effectiveness and transferability of the methodology were evaluated at three fish pass sites covering conditions of low, medium and high discharge. The methodology outputs enabled a detailed quantitative characterisation of the fish pass attraction flow and its interaction with other hydrodynamic features. The outputs are suitable to formulate novel indicators of hydrodynamic fish pass attractiveness and they revealed the need to refine traditional fish pass design guidelines.Item Open Access A framework for reviewing the trade-offs between, renewable energy, food, feed and wood production at a local level(Pergamon, 2012-01-31T00:00:00Z) Burgess, Paul J.; Rivas Casado, Monica; Gavu, Jerry; Mead, Andrew; Cockerill, Tim; Lord, Richard; van der Horst, Dan; Howard, David C.High fuel prices and concerns about energy security and anthropogenic climate change are encouraging a transition towards a low carbon economy. Although energy policy is typically set at a national level, tools are needed for people to engage with energy policy at regional and local levels, and to guide decisions regarding land use, distributed generation and energy supply and demand. The aim of this paper is to develop a per-capita approach to renewable energy demand and supply within a landscape and to illustrate the key trade-offs between renewable energy, food, (animal) feed and wood production. The chosen case study area (16,000 ha) of Marston Vale, England is anticipated to have a population density midway between that for England and the UK. The daily per capita demand for energy for heat (31 kWh), transport (34 kWh) and electricity (15 kWh) when combined (80 kWh) was seven-fold higher than the combined demand for food (2 kWh), animal feed (6 kWh), and wood (4 kWh). Using described algorithms, the combined potential energy supply from domestic wind and photovoltaic panels, solar heating, ground-source heat, and municipal waste was limited (<10 kWh p−1d−1). Additional electricity could be generated from landfill gas and commercial wind turbines, but these have temporal implications. Using a geographical information system and the Yield-SAFE tree and crop yield model, the capacity to supply bioethanol, biodiesel, and biomass, food, feed and wood was calculated and illustrated for three land-use scenarios. These scenarios highlight the limits on meeting energy demands for transport (33%) and heat (53%), even if all of the arable and grassland area was planted to a high yielding crop like wheat. The described framework therefore highlights the major constraints faced in meeting current UK energy demands from land-based renewable energy and the stark choices faced by decision makItem Open Access Geostatistical analysis of the spatial distribution of mycotoxin concentration in bulk cereals(Taylor & Francis, 2009-06-30T00:00:00Z) Rivas Casado, Monica; Parsons, David J.; Weightman, R. M.; Magan, Naresh; Origgi, S.Deoxynivalenol (DON) and ochratoxin A (OTA) in agricultural commodities present hazards to human and animal health. Bulk lots are routinely sampled for their presence, but it is widely acknowledged that designing sampling plans is particularly problematical because of the heterogeneous distribution of the mycotoxins. Previous studies have not take samples from bulk. Sampling plans are therefore designed on the assumption of random distributions. The objective of this study was to analyse the spatial distribution of DON and OTA in bulk commodities with geostatistics. This study was the first application of geostatistical analysis to data on mycotoxins contamination of bulk commodities. Data sets for DON and OTA in bulk storage were collected from the literature and personal communications, of which only one contained data suitable for geostatistical analysis. This data set represented a 26-tonne truck of wheat with a total of 100 sampled points. The mean concentrations of DON and OTA were 1342 and 0.59 mu g kg(-1), respectively. The results showed that DON presented spatial structure, whilst OTA was randomly distributed in space. This difference between DON and OTA probably reflected the fact that DON is produced in the field, whereas OTA is produced in storage. The presence of spatial structure for DON implies that sampling plans need to consider the location of sample points in addition to the number of points sampled in order to obtain reliable estimates of quantities such as the mean contamination.Item Open Access Guidelines for the use of unmanned aerial systems in flood emergency response(MDPI, 2020-02-13) Salmoral, Gloria; Rivas Casado, Monica; Muthusamy, Manoranjan; Butler, David; Menon, Prathyush P.; Leinster, PaulThere is increasing interest in using Unmanned Aircraft Systems (UAS) in flood risk management activities including in response to flood events. However, there is little evidence that they are used in a structured and strategic manner to best effect. An effective response to flooding is essential if lives are to be saved and suffering alleviated. This study evaluates how UAS can be used in the preparation for and response to flood emergencies and develops guidelines for their deployment before, during and after a flood event. A comprehensive literature review and interviews, with people with practical experience of flood risk management, compared the current organizational and operational structures for flood emergency response in both England and India, and developed a deployment analysis matrix of existing UAS applications. An online survey was carried out in England to assess how the technology could be further developed to meet flood emergency response needs. The deployment analysis matrix has the potential to be translated into an Indian context and other countries. Those organizations responsible for overseeing flood risk management activities including the response to flooding events will have to keep abreast of the rapid technological advances in UAS if they are to be used to best effect.Item Open Access High resolution orthomosaics of African coral reefs: a tool for wide-scale benthic monitoring(MDPI, 2017-07-08) Palma, Marco; Rivas Casado, Monica; Pantaleo, Ubaldo; Cerrano, CarloCoral reefs play a key role in coastal protection and habitat provision. They are also well known for their recreational value. Attempts to protect these ecosystems have not successfully stopped large-scale degradation. Significant efforts have been made by government and research organizations to ensure that coral reefs are monitored systematically to gain a deeper understanding of the causes, the effects and the extent of threats affecting coral reefs. However, further research is needed to fully understand the importance that sampling design has on coral reef characterization and assessment. This study examines the effect that sampling design has on the estimation of seascape metrics when coupling semi-autonomous underwater vehicles, structure-from-motion photogrammetry techniques and high resolution (0.4 cm) underwater imagery. For this purpose, we use FRAGSTATS v4 to estimate key seascape metrics that enable quantification of the area, density, edge, shape, contagion, interspersion and diversity of sessile organisms for a range of sampling scales (0.5 m × 0.5 m, 2 m × 2 m, 5 m × 5 m, 7 m × 7 m), quadrat densities (from 1–100 quadrats) and sampling strategies (nested vs. random) within a 1655 m2 case study area in Ponta do Ouro Partial Marine Reserve (Mozambique). Results show that the benthic community is rather disaggregated within a rocky matrix; the embedded patches frequently have a small size and a regular shape; and the population is highly represented by soft corals. The genus Acropora is the more frequent and shows bigger colonies in the group of hard corals. Each of the seascape metrics has specific requirements of the sampling scale and quadrat density for robust estimation. Overall, the majority of the metrics were accurately identified by sampling scales equal to or coarser than 5 m × 5 m and quadrat densities equal to or larger than 30. The study indicates that special attention needs to be dedicated to the design of coral reef monitoring programmes, with decisions being based on the seascape metrics and statistics being determined. The results presented here are representative of the eastern South Africa coral reefs and are expected to be transferable to coral reefs with similar characteristics. The work presented here is limited to one study site and further research is required to confirm the findings.Item Open Access Identifying non-stationary groundwater level response to North Atlantic ocean- atmosphere teleconnection patterns using wavelet coherence(Springer Science Business Media, 2011-12-31T00:00:00Z) Holman, Ian P.; Rivas Casado, Monica; Bloomfield, J. P.; Gurdak, J. J.The first comprehensive use of wavelet methods to identify non-stationary time- frequency relations between North Atlantic ocean-atmosphere teleconnection patterns and groundwater levels is described. Long-term hydrogeological time series from three boreholes within different aquifers across the UK are analysed to identify statistically significant wavelet coherence between the North Atlantic Oscillation, East Atlantic pattern, and the Scandinavia pattern and monthly groundwater-level time series. Wavelet coherence measures the cross- correlation of two time series as a function of frequency, and can be interpreted as a correlation coefficient value. Results not only indicate that there are common statistically significant periods of multiannual-to-decadal wavelet coherence between the three teleconnection indices and groundwater levels in each of the boreholes, but they also show that there are periods when groundwater levels at individual boreholes show distinctly different patterns of significant wavelet coherence with respect to the teleconnection indices. The analyses presented demonstrate the value of wave- let methods in identifying the synchronization of groundwater-level dynamics by non-stationary climate variability on time scales that range from interannual to decadal
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