Publications

Impact of land cover, rainfall and topography on flood risk in West Java

Published in Natural Hazards, 2023

Flooding represents around 32% of total disasters in Indonesia and disproportionately affects the poorest of communities. The objective of this study was to determine significant statistical differences, in terms of river catchment characteristics, between regions in West Java that reported suffering from flood disasters and those that did not. Catchment characteristics considered included various statistical measures of topography, land-use, soil-type, meteorology and river flow rates. West Java comprises 154 level 9 HydroSHEDS sub-basin regions. We split these regions into those where flood disasters were reported and those where they were not, for the period of 2009 to 2013. Rainfall statistics were derived using the CHIRPS gridded precipitation data package. Statistical estimates of river flow rates, applicable to ungauged catchments, were derived from regionalisation relation- ships obtained by stepwise linear regression with river flow data from 70 West Javanese gauging stations. We used Kolmogorov–Smirnov tests to identify catchment characteristics that exhibit significant statistical differences between the two sets of regions. Median annual maximum river flow rate (AMRFR) was found to be positively correlated with plantation cover. Reducing plantation land cover from 20 to 10% was found to lead to a modelled 38% reduction in median AMRFR. AMRFR with return periods greater than 10 years were found to be negatively correlated with wetland farming land cover, suggesting that rice paddies play an important role in attenuating extreme river flow events. Nevertheless, the Kolmogorov–Smirnov tests revealed that built land cover is the most important factor defining whether or not an area is likely to report flood disasters in West Java. This is presumably because the more built land cover, the more people available to experience and report flood disasters. Our findings also suggest that more research is needed to understand the important role of plantation cover in aggravating median annual maximum river flow rates and wetland farming cover in mitigating extreme river flow events.

Recommended citation: Rahayu R., Mathias, S. A., Reaney S., Vesuviano G., Suwarman R., Ramdhan A. M. (2023) Impact of land cover, rainfall and topography on flood risk in West Java. Natural Hazards 116, 1735–1758 https://doi.org/10.1007/s11069-022-05737-6

Identification of floodwater source areas in Nepal using SCIMAP-Flood

Published in Journal of Flood Risk Management, 2022

Practical approaches for managing flooding from fluvial sources are moving away from mitigation solely at the point of impact and towards integrated catchment management. This considers the source areas, flow pathways of floodwaters and the locations and exposure to the risk of communities. For a field site in southern Nepal, we analyse catchment response to a range of simulated rainfall events, which when evaluated collectively can help guide potential flood management solutions. This is achieved through the adoption of SCIMAP-Flood, a decision support framework that works at the catchment-scale to identify critical source areas for floodwaters. The SCIMAP-Flood Fitted inverse modelling approach has been applied to the East Rapti catchment, Nepal. For multiple flood impact locations throughout the catchment, SCIMAP-Flood effectively identifies locations where flood management measures would have the most positive effects on risk reduction. The results show that the spatial targeting of mitigation measures in areas of irrigated and rainfed agriculture and the prevention of deforestation or removal of shrubland would be the most effective approaches. If these actions were in the upper catchment above Hetauda or upstream of Manahari they would have the most effective reduction in the flood peak.

Recommended citation: Pearson C. J., Reaney S. M.,Perks M. T.,Hortobagyi B., Rosser N. J. and Large A. R. G. 2022: Identification of floodwater source areas in Nepal using SCIMAP-Flood, Journal of Flood Risk Management https://doi.org/10.1111/jfr3.12840

Sustainable Catchment-Wide Flood Management: A Review of the Terminology and Application of Sustainable Catchment Flood Management Techniques in the UK

Published in Water, 2022

Climate change has seen increased pressures put on the existing ageing flood mitigation infrastructure. As a result, over recent decades there has been a shift from traditional hard-engineered approaches to flooding to more sustainable methods that utilise nature-based processes in order to slow flow, store water and increase infiltration. Doing so has resulted in a range of different nomenclature for such techniques, particularly in the rural environment. This paper takes a critical review of such terms to draw parallels in the different approaches, with the aim of developing a more unified, consistent approach to flood management. Furthermore, links have been drawn with the urban environment, where Sustainable Drainage Systems (SuDS) are used as a sustainable approach to urban flooding. The findings from this review have identified a series of issues that result from the current UK approach of differentiating between urban and rural flood risk, with funding often given for Natural Flood Management (NFM) projects separately to SuDS, with little integrated thinking from source to sea. Hence, the review suggests:

1. A greater consideration of scale, focusing on the catchment as a whole, is required to ensure a more holistic approach to flood management, under the phrase “sustainable catchment-wide flood management”, to ensure that the focus shifts from NFM (rural) and SuDS (urban), to a more integrated catchment-wide approach;
2. The development of robust policy and regulatory framework, to ensure that such an approach is more widely adopted;
3. A greater consideration of the long-term costs is also required, with future research needed on the long-term maintenance costs of different methods;
4. The development of modelling approaches that can simulate flow at a range of spatial and temporal scales, to support stakeholders, such as local authorities, flood risk engineers and government agencies when considering flow not only in rural areas, but also to understand the impact beyond the immediate area around the scheme.

Recommended citation: Lashford, C.; Lavers, T.; Reaney, S.; Charlesworth, S.; Burgess-Gamble, L.; Dale, J. 2022: Sustainable Catchment-Wide Flood Management: A Review of the Terminology and Application of Sustainable Catchment Flood Management Techniques in the UK. _Water_, 14, 1204. https://doi.org/10.3390/w14081204

Spatial targeting of nature‐based solutions for flood risk management within river catchments

Published in Journal of Flood Risk Management, 2022

A wide range of nature-based solutions for flood hazard management work by storing and slowing flow within catchments, and therefore, there is a need to identify the optimal locations for implementing these solutions. This paper presents a relative scoring-based mapping of the likely locations that contribute to the flood peak. Targeting flow reduction and attenuating mitigation actions in these locations can be an effective way to reduce flood damages at impact points downstream. The presented tool, SCIMAP-Flood, uses information on land cover, hydrological connectivity, flood generating rainfall patterns and hydrological travel time distributions to impacted communities to find the potential source areas of flood waters. The importance of each location in the catchment is weighted based on its contribution to the flood hazard at each of the downstream impact points. In the example application, SCIMAP-Flood is applied at a 5-m grid resolution for the River Eden catchment, Cumbria, England, to provide sub-field scale information at the landscape extent. Therefore, the tool can identify sub-catchments where more detailed work can test different mitigation measures.

Recommended citation: Reaney, Sim M. (2022) Spatial targeting of nature‐based solutions for flood risk management within river catchments. Journal of Flood Risk Management Volume 15, Issue 3 e12803 https://doi.org/10.1111/jfr3.12803

Catchment Models and Management Tools for Diffuse Contaminants (Sediment, Phosphorus and Pesticides): DiffuseTools Project

Published in Irish EPA Technical Reports, 2021

Agricultural pollution continues to be a major cause of eutrophication of waterbodies and water quality degradation in Ireland and internationally, with the success of mitigation measures hampered by the diffusivity of pollution sources and pathways. Ireland must meet international water quality obligations set by the EU Water Framework Directive (WFD), with the aim of achieving “good ecological and chemical status” in all and high status in some High Status Objective (HSO) waterbodies by 2027. For surface waters, S.I. 272 sets out the required standards. Good ecological status is assessed using environmental quality standards, including an annual mean unfiltered reactive phosphorus (P) concentration not exceeding 0.035mgl ^–1 in Irish rivers. The WFD includes provisions from the Nitrates Directive that aimed to protect waterbodies from agricultural nitrogen and P pollution by implementing a Nitrates Action Programme and S.I. 605, Good Agricultural Practice for Protection of Waters Regulations. The most recent Environmental Protection Agency (EPA) water quality assessment over the period 2013–2018 found that 52.8% of surface waterbodies assessed are of good or high ecological status (a decline of 2.6% compared with 2010–2015), with the remaining (47.2%) being of moderate, poor or bad ecological status. This has given rise to concerns that the current mitigation measures, which in the past have been heavily source focused, do not go far enough, and has led to renewed interest in the development of decision support tools (DSTs) for P loss management. These can spatially map P, sediment and pesticide losses from agricultural land to waterbodies at high resolution and are needed by farmers, catchment managers, policymakers and water agencies to improve cost-effective targeting of pollution mitigation measures. The University College Dublin (UCD)-led DiffuseTools project has developed such modelling tools suitable for implementation nationally to estimate P and sediment losses from diffuse sources and their delivery points to surface waters using the latest data, science and geographical information systems (GISs).

Recommended citation: Thomas I., Bruen M., Mockler E., Werner C., Mellander P., Reaney S., Rymszewicz A., McGrath G., Eder E., Wade A., Collins A. and Arheimer B. 2021: "Catchment Models and Management Tools for Diffuse Contaminants (Sediment, Phosphorus and Pesticides): DiffuseTools Project" *Irish EPA Research Report no. 396*. ISBN: 978-1-84095-011-8

Transmission loss estimation for ephemeral sand rivers in Southern Africa

Published in Journal of Hydrology, 2021

Ephemeral sand rivers represent an important water resource in Southern Africa. These rivers only flow for a few days in a year. However, much of this water infiltrates the underlying river bed sediments where it is protected from evaporation and utilized by farmers throughout the dry season. Despite their importance, little is known about how much recoverable water is annually stored within the sand. A particular difficulty concerns obtaining reliable estimates of transmission losses (the amount of water that infiltrates the river bed). The objective of this article was to develop an improved methodology for quantifying transmission loss from ephemeral sand rivers by calibrating a lumped rainfall-runoff model to observed river flow data. Fifteen years of daily river flow data were obtained from four sand rivers in Botswana, namely, Shahshe, Ntshe, Tati and Metsimotlhabe. These data were supplemented with meteorological data from AgMERRA (Ruane et al., 2015) and precipitation data from CHIRPS (Funk et al., 2015). Our simplified rainfall runoff model had four unknown parameters including a river bed infiltration factor, a surface storage capacity, a river bed storage capacity and an average river channel width. Posteriori parameter distributions were derived using a GLUE (Beven and Binley, 1992) methodology. Our study confirms that upper and lower bounds for transmission loss can be obtained by calibrating a lumped rainfall runoff model to a single set of river flow gauging data. Transmission loss was found to represent between 55% and 85% of the total surface runoff at these locations.

Recommended citation: Mathias S. A., Reaney S. M. and Kenabatho P. K. 2021: "Transmission loss estimation for ephemeral sand rivers in Southern Africa." Journal of Hydrology, Volume 600, September 2021, 126487.

A new framework for integrated, holistic, and transparent evaluation of inter-basin water transfer schemes

Published in Science of The Total Environment, 2020

“Water shortages are forecast to affect 50% of the world’s population by 2030, impacting developing nations most acutely. To increase water security there has been a significant increase in Inter-basin Water Transfer (IBWT) schemes, engineering mega-projects that redistribute water from one basin to another. However, the implementation of these schemes is often contested, and evaluation of their complex impacts inadequate, or hidden from full public scrutiny. There is an urgent need to develop more integrated, holistic, and transparent ways of evaluating the multiple interlinking impacts of IBWT schemes of this scale. In this paper, we address this gap by outlining an experimental methodology to evaluate IBWT schemes using a multidisciplinary and transparent methodology which utilises publicly available data. We illustrate the method using a case study from the Inter-Linking Rivers Project in Northern India, comparing the results of the experimental approach against the official analysis of the proposed scheme produced by the State Government of Jharkhand. The results demonstrate that the proposed experimental method allows more detailed evaluation of spatial and temporal variability in water availability and demand, as well as holistic evaluation of the functioning of the proposed scheme under different future scenarios. Based on these results we propose a flexible framework for future evaluation of proposed water transfer schemes which embeds the principles of integrated assessment, transparency, and sound science which can be adapted to other IBWT projects across the world.”

Recommended citation: Sinha P., Rollason E., Bracken L. J., Wainwright J., Reaney S. M., 2020: "A new framework for integrated, holistic, and transparent evaluation of inter-basin water transfer schemes." Science of The Total Environment, Volume 721, 15 June 2020, 137646.

Identifying critical source areas using multiple methods for effective diffuse pollution mitigation

Published in Journal of Environmental Management, 2019

“Diffuse pollution from agriculture constitutes a key pressure on the water quality of freshwaters and is frequently the cause of ecological degradation. The problem of diffuse pollution can be conceptualised with a source-mobilisation-pathway (or delivery)-impact model, whereby the combination of high source risk and strong connected pathways leads to ‘critical source areas’ (CSAs). These areas are where most diffuse pollution will originate, and hence are the optimal places to implement mitigation measures. However, identifying the locations of these areas is a key problem across different spatial scales within catchments. A number of approaches are frequently used for this assessment, although comparisons of these assessments are rarely carried out. We evaluate the CSAs identified via traditional walkover surveys supported by three different approaches, highlighting their benefits and disadvantages. These include a custom designed smartphone app; a desktop geographic information system (GIS) and terrain analysis-based SCIMAP (Sensitive Catchment Integrated Modelling and Analysis Platform) approach; and the use of a high spatial resolution drone dataset as an improved input data for SCIMAP modelling. Each of these methods captures the locations of the CSAs, revealing similarities and differences in the prioritisation of CSA features. The differences are due to the temporal and spatial resolution of the three methods such as the use of static land cover information, the ability to capture small scale features, such as gateways and the incomplete catchment coverage of the walkover survey. The relative costs and output resolutions of the three methods indicate that they are suitable for application at different catchment scales in conjunction with other methods. Based on the results in this paper, it is recommended that a multi-evidence-based approach to diffuse pollution management is taken across catchment spatial scales, incorporating local knowledge from the walkover with the different data resolutions of the SCIMAP approach.”

Recommended citation: Reaney, S.M., Mackay, E.B., Haygarth, P.M., Fisher, M., Molineux, A., Potts, M. & Benskin, C. McW.H. Identifying critical source areas using multiple methods for effective diffuse pollution mitigation. Journal of Environmental Management. 2019;250:109366

Benchmarking the predictive capability of hydrological models for river flow and flood peak predictions across over 1000 catchments in Great Britain

Published in Hydrology and Earth System Science, 2019

“Benchmarking model performance across large samples of catchments is useful to guide model selection and future model development. Given uncertainties in the observational data we use to drive and evaluate hydrological models, and uncertainties in the structure and parameterisation of models we use to produce hydrological simulations and predictions, it is essential that model evaluation is undertaken within an uncertainty analysis framework. Here, we benchmark the capability of several lumped hydrological models across Great Britain by focusing on daily flow and peak flow simulation. Four hydrological model structures from the Framework for Understanding Structural Errors (FUSE) were applied to over 1000 catchments in England, Wales and Scotland. Model performance was then evaluated using standard performance metrics for daily flows and novel performance metrics for peak flows considering parameter uncertainty.

Recommended citation: Rosanna A. Lane, Gemma Coxon, Jim E. Freer, Thorsten Wagener, Penny J. Johnes, John P. Bloomfield, Sheila Greene, Christopher J. A. Macleod & Sim M. Reaney 2019: Benchmarking the predictive capability of hydrological models for river flow and flood peak predictions across over 1000 catchments in Great Britain. Hydrology and Earth System Science. 23:4011-4032.

Strong and recurring seasonality revealed within stream diatom assemblages

Published in SCIENTIFIC REPORTS, 2019

“Improving stream water quality in agricultural landscapes is an ecological priority and a legislative duty for many governments. Ecosystem health can be effectively characterised by organisms sensitive to water quality changes such as diatoms, single-celled algae that are a ubiquitous component of stream benthos. Diatoms respond within daily timescales to variables including light, temperature, nutrient availability and flow conditions that result from weather and land use characteristics. However, little consideration has been given to the ecological dynamics of diatoms through repeated seasonal cycles when assessing trajectories of stream function, even in catchments actively managed to reduce human pressures. Here, six years of monthly diatom samples from three independent streams, each receiving differing levels of diffuse agricultural pollution, reveal robust and repeated seasonal variation. Predicted seasonal changes in climate-related variables and anticipated ecological impacts must be fully captured in future ecological and water quality assessments, if the apparent resistance of stream ecosystems to pollution mitigation measures is to be better understood.”

Recommended citation: M. Snell, P. Barker, B. Surridge, C. Benskin, N. Barber, S. Reaney, W. Tych, D. Mindham, A. Large, S. Burke, P. Haygarth, "Strong and recurring seasonality revealed within stream diatom assemblages." SCIENTIFIC REPORTS, 2019.

High resolution characterisation of E. coli proliferation profiles in livestock faeces

Published in WASTE MANAGEMENT, 2019

“Agricultural intensification can lead to high volumes of livestock faeces being applied to land, either as solid or liquid manures or via direct defecation, and can result in reservoirs of faecal indicator organisms (FIOs) persisting within farmland. Understanding the survival of FIOs, e.g. E. coli, in agricultural environments, and in particular within different livestock faeces, is key to developing catchment management practices for the protection of ecosystem services provided by clean water. Frequently, controlled laboratory studies, under constant temperature regimes, are used to determine the impact of environmental factors on E. coli persistence in livestock faeces; however, such studies oversimplify the diurnal variations and interactions of real world conditions. The aim of this study was to investigate the survival of E. coli using a controlled environment facility, which simulated diurnal variation of temperatures typically experienced during a British spring and summer. The approach provided a comparison of E. coli persistence profiles within faeces of sheep, beef cattle and dairy cattle to allow novel interpretations of E. coli regrowth patterns in contrasting livestock faeces in the period immediately post-defecation. Thus, the coupling of a tightly controlled environment facility with high resolution monitoring enabled the development of a new non-linear, asymptotic description of E. coli proliferation in livestock faeces, with increased potential for E. coli growth observed during warmer temperatures for all livestock types. While this study focused on temperatures typical of the UK, the occurrence of a phase of E. coli regrowth has implications for microbial water quality management worldwide. (C) 2019 The Authors. Published by Elsevier Ltd..”

Recommended citation: Kenneth Porter, Richard Quilliam, Sim Reaney, David Oliver, "High resolution characterisation of E. coli proliferation profiles in livestock faeces." WASTE MANAGEMENT, 2019.

The Role of Attenuation and Land Management in Small Catchments to Remove Sediment and Phosphorus: A Modelling Study of Mitigation Options and Impacts

Published in WATER, 2018

“It is well known that soil, hillslopes, and watercourses in small catchments possess a degree of natural attenuation that affects both the shape of the outlet hydrograph and the transport of nutrients and sediments. The widespread adoption of Natural Based Solutions (NBS) practices in the headwaters of these catchments is expected to add additional attenuation primarily through increasing the amount of new storage available to accommodate flood flows. The actual type of NBS features used to add storage could include swales, ditches, and small ponds (acting as sediment traps). Here, recent data collected from monitored features (from the Demonstration Test Catchments project in the Newby Beck catchment (Eden) in northwest England) were used to provide first estimates of the percentages of the suspended sediment (SS) and total phosphorus (TP) loads that could be trapped by additional features. The Catchment Runoff Attenuation Flux Tool (CRAFT) was then used to model this catchment (Newby Beck) to investigate whether adding additional attenuation, along with the ability to trap and retain SS (and attached P), will have any effect on the flood peak and associated peak concentrations of SS and TP. The modelling tested the hypothesis that increasing the amount of new storage (thus adding attenuation capacity) in the catchment will have a beneficial effect. The model results implied that a small decrease of the order of 5-10% in the peak concentrations of SS and TP was observable after adding 2000 m(3) to 8000 m(3) of additional storage to the catchment..”

Recommended citation: Russell Adams, Paul Quinn, Nick Barber, Sim Reaney, "The Role of Attenuation and Land Management in Small Catchments to Remove Sediment and Phosphorus: A Modelling Study of Mitigation Options and Impacts." WATER, 2018.

A catchment-scale model to predict spatial and temporal burden of E. coli on pasture from grazing livestock

Published in SCIENCE OF THE TOTAL ENVIRONMENT, 2018

“Effective management of diffuse microbial water pollution from agriculture requires a fundamental understanding of how spatial patterns of microbial pollutants, e.g. E. coli, vary over time at the landscape scale. The aim of this study was to apply the Visualising Pathogen & Environmental Risk (ViPER) model, developed to predict E. coli burden on agricultural land, in a spatially distributed manner to two contrasting catchments in order to map and understand changes in E. coli burden contributed to land from grazing livestock. The model was applied to the River Ayr and Lunan Water catchments, with significant correlations observed between area of improved grassland and the maximum total E. coli per 1 km(2) grid cell (Ayr: r = 0.57; p < 0.001, Lunan: r = 0.32; p < 0.001). There was a significant difference in the predicted maximum E. coli burden between seasons in both catchments, with summer and autumn predicted to accrue higher E. coli contributions relative to spring and winter (P < 0.001), driven largely by livestock presence. The ViPER model thus describes, at the landscape scale, spatial nuances in the vulnerability of E. coli loading to land as driven by stocking density and livestock grazing regimes. Resulting risk maps therefore provide the underpinning evidence to inform spatially-targeted decision-making with respect to managing sources of E. coli in agricultural environments. (c) 2017 The Author(s). Published by Elsevier B.V..”

Recommended citation: David Oliver, Phil Bartie, A. Heathwaite, Sim Reaney, Jared Parnell, Richard Quilliam, "A catchment-scale model to predict spatial and temporal burden of E. coli on pasture from grazing livestock." SCIENCE OF THE TOTAL ENVIRONMENT, 2018.

Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management

Published in JOURNAL OF ENVIRONMENTAL MANAGEMENT, 2017

“Under the EU Water Framework Directive, suspended sediment is omitted from environmental quality standards and compliance targets. This omission is partly explained by difficulties in assessing the complex dose-response of ecological communities. But equally, it is hindered by a lack of spatially distributed estimates of suspended sediment variability across catchments. In this paper, we demonstrate the inability of traditional, discrete sampling campaigns for assessing exposure to fine sediment. Sampling frequencies based on Environmental Quality Standard protocols, whilst reflecting typical manual sampling constraints, are unable to determine the magnitude of sediment exposure with an acceptable level of precision. Deviations from actual concentrations range between -35 and +20% based on the interquartile range of simulations. As an alternative, we assess the value of low-cost,, suspended sediment sampling networks for quantifying suspended sediment transfer (SST). In this study of the 362 km(2) upland Esk catchment we observe that spatial patterns of sediment flux are consistent over the two year monitoring period across a network of 17 monitoring sites. This enables the key contributing sub-catchments of Butter Beck (SST: 1141 t km(2) yr(-1)) and Glaisdale Beck (SST: 841 t km(2) yr(-1)) to be identified. The time -integrated samplers offer a feasible alternative to traditional infrequent and discrete sampling approaches for assessing spatio-temporal changes in contamination. In conjunction with a spatially distributed diffuse pollution model (SCIMAP), time-integrated sediment sampling is an effective means of identifying critical sediment source areas in the catchment, which can better inform sediment management strategies for pollution prevention and control. (C) 2017 Elsevier Ltd. All rights reserved..”

Recommended citation: M. Perks, J. Warburton, L. Bracken, S. Reaney, S. Emery, S. Hirst, "Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management." JOURNAL OF ENVIRONMENTAL MANAGEMENT, 2017.

Predicting diffuse microbial pollution risk across catchments: The performance of SCIMAP and recommendations for future development

Published in SCIENCE OF THE TOTAL ENVIRONMENT, 2017

“Microbial pollution of surface waters in agricultural catchments can be a consequence of poor farm management practices, such as excessive stocking of livestock on vulnerable land or inappropriate handling of manures and slurries. Catchment interventions such as fencing of watercourses, streamside buffer strips and constructed wetlands have the potential to reduce faecal pollution of watercourses. However these interventions are expensive and occupy valuable productive land. There is, therefore, a requirement for tools to assist in the spatial targeting of such interventions to areas where they will have the biggest impact on water quality improvements whist occupying the minimal amount of productive land. SCIMAP is a risk-based model that has been developed for this purpose but with a focus on diffuse sediment and nutrient pollution. In this study we investigated the performance of SCIMAP in predicting microbial pollution of watercourses and assessed modelled outputs of E. coli, a common faecal indicator organism (FIO), against observed water quality information. SCIMAP was applied to two river catchments in the UK. SCIMAP uses land cover riskweightings, which are routed through the landscape based on hydrological connectivity to generate catchment scale maps of relative in-stream pollution risk. Assessment of the model's performance and derivation of optimum land cover risk weightings was achieved using a Monte-Carlo sampling approach. Performance of the SCIMAP framework for informing on FIO risk was variable with better performance in the Yealm catchment (r(s) = 0.88; p < 0.01) than the Wyre (r(s) = -0.36; p > 0.05). Across both catchments much uncertainty was associated with the application of optimum risk weightings attributed to different land use classes. Overall, SCIMAP showed potential as a useful tool in the spatial targeting of FIO diffuse pollution management strategies; however, improvements are required to transition the existing SCIMAP framework to a robust FIO risk-mapping tool. (C) 2017 The Authors. Published by Elsevier B.V..”

Recommended citation: Porter K., Reaney S. M., Quilliam R., Burgess C., Oliver D.: 2017: "Predicting diffuse microbial pollution risk across catchments: The performance of SCIMAP and recommendations for future development." SCIENCE OF THE TOTAL ENVIRONMENT, Volume 609, 31 December 2017, Pages 456-465

Predicting microbial water quality with models: Over-arching questions for managing risk in agricultural catchments

Published in SCIENCE OF THE TOTAL ENVIRONMENT, 2016

“The application of models to predict concentrations of faecal indicator organisms (FIOs) in environmental systems plays an important role for guiding decision-making associated with the management of microbial water quality. In recent years there has been an increasing demand by policy-makers for models to help inform FIO dynamics in order to prioritise efforts for environmental and human-health protection. However, given the limited evidence-base on which FIO models are built relative to other agricultural pollutants (e.g. nutrients) it is imperative that the end-user expectations of FIO models are appropriately managed. In response, this commentary highlights four over-arching questions associated with: (i) model purpose; (ii) modelling approach; (iii) data availability; and (iv) model application, that must be considered as part of good practice prior to the deployment of any modelling approach to predict FIO behaviour in catchment systems. A series of short and longer-term research priorities are proposed in response to these questions in order to promote better model deployment in the field of catchment microbial dynamics. (C) 2015 The Authors. Published by Elsevier B.V..”

Recommended citation: David Oliver, Kenneth Porter, Yakov Pachepsky, Richard Muirhead, Sim Reaney, Rory Coffey, David Kay, David Milledge, Eunmi Hong, Steven Anthony, Trevor Page, Jack Bloodworth, Per-Erik Mellander, Patrice Carbonneau, Scott McGrane, Richard Quilliam, "Predicting microbial water quality with models: Over-arching questions for managing risk in agricultural catchments." SCIENCE OF THE TOTAL ENVIRONMENT, 2016.

Changing climate and nutrient transfers: Evidence from high temporal resolution concentration-flow dynamics in headwater catchments

Published in SCIENCE OF THE TOTAL ENVIRONMENT, 2016

“We hypothesise that climate change, together with intensive agricultural systems, will increase the transfer of pollutants from land to water and impact on stream health. This study builds, for the first time, an integrated assessment of nutrient transfers, bringing together a) high-frequency data from the outlets of two surface water dominated, headwater (similar to 10 km(2)) agricultural catchments, b) event-by-event analysis of nutrient transfers, c) concentration duration curves for comparison with EU Water Framework Directive water quality targets, d) event analysis of location-specific, sub-daily rainfall projections (UKCP, 2009), and e) a linear model relating storm rainfall to phosphorus load. These components, in combination, bring innovation and new insight into the estimation of future phosphorus transfers, which was not available from individual components. The data demonstrated two features of particular concern for climate change impacts. Firstly, the bulk of the suspended sediment and total phosphorus (TP) load (greater than 90% and 80% respectively) was transferred during the highest discharge events. The linear model of rainfall-driven TP transfers estimated that, with the projected increase in winter rainfall (+ 8% to + 17% in the catchments by 2050s), annual event loads might increase by around 9% on average, if agricultural practices remain unchanged. Secondly, events following dry periods of several weeks, particularly in summer, were responsible for high concentrations of phosphorus, but relatively low loads. The high concentrations, associated with low flow, could become more frequent or last longer in the future, with a corresponding increase in the length of time that threshold concentrations (e.g. for water quality status) are exceeded. The results suggest that in order to build resilience in stream health and help mitigate potential increases in diffuse agricultural water pollution due to climate change, land management practices should target controllable risk factors, such as soil nutrient status, soil condition and crop cover. (C) 2016 Elsevier B.V. All rights reserved..”

Recommended citation: M. Ockenden, C. Deasy, C. Benskin, K. Beven, S. Burke, A. Collins, R. Evans, P. Falloon, K. Forber, K. Hiscock, M. Hollaway, R. Kahana, C. Macleod, S. Reaney, M. Snell, M. Villamizar, C. Wearing, P. Withers, J. Zhou, P. Haygarth, "Changing climate and nutrient transfers: Evidence from high temporal resolution concentration-flow dynamics in headwater catchments." SCIENCE OF THE TOTAL ENVIRONMENT, 2016.

Dominant mechanisms for the delivery of fine sediment and phosphorus to fluvial networks draining grassland dominated headwater catchments

Published in SCIENCE OF THE TOTAL ENVIRONMENT, 2015

“Recent advances in monitoring technology have enabled high frequency, in-situ measurements of total phosphorus and total reactive phosphorus to be undertaken with high precision, whilst turbidity can provide an excellent surrogate for suspended sediment. Despite these measurements being fundamental to understanding the mechanisms and flow paths that deliver these constituents to river networks, there is a paucity of such data for headwater agricultural catchments. The aim of this paper is to deduce the dominant mechanisms for the delivery of fine sediment and phosphorus to an upland river network in the UK through characterisation of the temporal variability of hydrological fluxes, and associated soluble and particulate concentrations for the period spanning March 2012-February 2013. An assessment of the factors producing constituent hysteresis is undertaken following factor analysis (FA) on a suite of measured environmental variables representing the fluvial and wider catchment conditions prior to, and during catchment-wide hydrological events. Analysis indicates that suspended sediment is delivered to the fluvial system predominantly via rapidly responding pathways driven by event hydrology. However, evidence of complex, figure-of-eight hysteresis is observed following periods of hydrological quiescence, highlighting the importance of preparatory processes. Sediment delivery via a slow moving, probably sub-surface pathway does occur, albeit infrequently and during low magnitude events at the catchment outlet. Phosphorus is revealed to have a distinct hysteretic response to that of suspended sediment, with sub-surface pathways dominating. However, high magnitude events were observed to exhibit threshold-like behaviour, whereby activation and connection of usually disconnected depositional zones to the fluvial networks results in the movement of vast phosphorus fluxes. Multiple pathways are observed for particulate and soluble constituents, highlighting the challenges faced in mitigating the delivery of contaminant fluxes to headwater river systems. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved..”

Recommended citation: M. Perks, G. Owen, C. Benskin, J. Jonczyk, C. Deasy, S. Burke, S. Reaney, P. Haygarth, "Dominant mechanisms for the delivery of fine sediment and phosphorus to fluvial networks draining grassland dominated headwater catchments." SCIENCE OF THE TOTAL ENVIRONMENT, 2015.

A geospatial framework to support integrated biogeochemical modelling in the United Kingdom

Published in ENVIRONMENTAL MODELLING & SOFTWARE, 2015

“Anthropogenic impacts on the aquatic environment, especially in the context of nutrients, provide a major challenge for water resource management. The heterogeneous nature of policy relevant management units (e.g. catchments), in terms of environmental controls on nutrient source and transport, leads to the need for holistic management. However, current strategies are limited by current understanding and knowledge that is transferable between spatial scales and landscape typologies. This study presents a spatially-explicit framework to support the modelling of nutrients from land to water, encompassing environmental and spatial complexities. The framework recognises nine homogeneous landscape units, distinct in terms of sensitivity of nutrient losses to waterbodies. The functionality of the framework is demonstrated by supporting an exemplar nutrient model, applied within the Environmental Virtual Observatory pilot (EVOp) cloud cyber-infrastructure. We demonstrate scope for the use of the framework as a management decision support tool and for further development of integrated biogeochemical modelling. (C) 2015 The Authors. Published by Elsevier Ltd..”

Recommended citation: Greene S., Johnes P., Bloomfield J., Reaney S., Lawley R., Elkhatib Y., Freer J., Odoni N., Macleod C., Percy B.: 2015: A geospatial framework to support integrated biogeochemical modelling in the United Kingdom." Environmental Modelling & Software, 68, 219-232

The role of tributary relative timing and sequencing in controlling large floods

Published in WATER RESOURCES RESEARCH, 2014

“Hydrograph convolution is a product of tributary inputs from across the watershed. The time-space distribution of precipitation, the biophysical processes that control the conversion of precipitation to runoff and channel flow conveyance processes, are heterogeneous and different areas respond to rainfall in different ways. We take a subwatershed approach to this and account for tributary flow magnitude, relative timing, and sequencing. We hypothesize that as the scale of the watershed increases so we may start to see systematic differences in subwatershed hydrological response. We test this hypothesis for a large flood (T > 100 years) in a large watershed in northern England. We undertake a sensitivity analysis of the effects of changing subwatershed hydrological response using a hydraulic model. Delaying upstream tributary peak flow timing to make them asynchronous from downstream subwatersheds reduced flood magnitude. However, significant hydrograph adjustment in any one subwatershed was needed for meaningful reductions in stage downstream, although smaller adjustments in multiple tributaries resulted in comparable impacts. For larger hydrograph adjustments, the effect of changing the timing of two tributaries together was lower than the effect of changing each one separately. For smaller adjustments synergy between two subwatersheds meant the effect of changing them together could be greater than the sum of the parts. Thus, this work shows that while the effects of modifying biophysical catchment properties diminishes with scale due to dilution effects, their impact on relative timing of tributaries may, if applied in the right locations, be an important element of flood management..”

Recommended citation: Pattison I., Lane S. N., Hardy R., Reaney S. M., "The role of tributary relative timing and sequencing in controlling large floods." WATER RESOURCES RESEARCH, 2014. 50 (7) 5444-5458. https://doi.org/10.1002/2013WR014067

The importance of surface controls on overland flow connectivity in semi-arid environments: results from a numerical experimental approach

Published in HYDROLOGICAL PROCESSES, 2014

“In semi-arid environments, the characteristics of the land surface determine how rainfall is transformed into surface runoff and influences how this runoff moves from the hillslopes into river channels. Whether or not water reaches the river channel is determined by the hydrological connectivity. This paper uses a numerical experiment-based approach to systematically assess the effects of slope length, gradient, flow path convergence, infiltration rates and vegetation patterns on the generation and connectivity of runoff. The experiments were performed with the Connectivity of Runoff Model, 2D version distributed, physically based, hydrological model. The experiments presented are set within a semi-arid environment, characteristic of south-eastern Spain, which is subject to low frequency high rainfall intensity storm events. As a result, the dominant hydrological processes are infiltration excess runoff generation and surface flow dynamics. The results from the modelling experiments demonstrate that three surface factors are important in determining the form of the discharge hydrograph: the slope length, the slope gradient and the infiltration characteristics at the hillslope-channel connection. These factors are all related to the time required for generated runoff to reach an efficient flow channel, because once in this channel, the transmission losses significantly decrease. Because these factors are distributed across the landscape, they have a fundamental role in controlling the landscape hydrological response to storm events. Copyright (c) 2013 John Wiley & Sons, Ltd..”

Recommended citation: S. Reaney, L. Bracken, M. Kirkby, "The importance of surface controls on overland flow connectivity in semi-arid environments: results from a numerical experimental approach." HYDROLOGICAL PROCESSES, 2014.

High frequency variability of environmental drivers determining benthic community dynamics in headwater streams

Published in ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS, 2014

“Headwater streams are an important feature of the landscape, with their diversity in structure and associated ecological function providing a potential natural buffer against downstream nutrient export. Phytobenthic communities, dominated in many headwaters by diatoms, must respond to physical and chemical parameters that can vary in magnitude within hours, whereas the ecological regeneration times are much longer. How diatom communities develop in the fluctuating, dynamic environments characteristic of headwaters is poorly understood. Deployment of near- continuous monitoring technology in sub-catchments of the River Eden, NW England, provides the opportunity for measurement of temporal variability in stream discharge and nutrient resource supply to benthic communities, as represented by monthly diatom samples collected over two years. Our data suggest that the diatom communities and the derived Trophic Diatom Index, best reflect stream discharge conditions over the preceding 18-21 days and Total Phosphorus concentrations over a wider antecedent window of 7-21 days. This is one of the first quantitative assessments of long-term diatom community development in response to continuously-measured stream nutrient concentration and discharge fluctuations. The data reveal the sensitivity of these headwater communities to mean conditions prior to sampling, with flow as the dominant variable. With sufficient understanding of the role of antecedent conditions, these methods can be used to inform interpretation of monitoring data, including those collected under the European Water Framework Directive and related mitigation efforts..”

Recommended citation: M. Snell, P. Barker, B. Surridge, A. Large, J. Jonczyk, C. Benskin, S. Reaney, M. Perks, G. Owen, W. Cleasby, C. Deasy, S. Burke, P. Haygarth, "High frequency variability of environmental drivers determining benthic community dynamics in headwater streams." ENVIRONMENTAL SCIENCE-PROCESSES &amp; IMPACTS, 2014.

Towards a unified threshold-based hydrological theory: necessary components and recurring challenges

Published in HYDROLOGICAL PROCESSES, 2013

Extrapolating the influence of local runoff generation processes to larger watershed scales has not always proven successful (Sivapalan, 2003; Kirchner, 2006; McDonnell et al., 2007). This has led to a call among hydrologists for research frameworks within which to pose questions, choose methodology, and shape interpretation and analysis of hydrological behaviour for advancing our understanding of watershed scale processes. In recent years, a shift towards focusing on catchment emergent properties and developing a unified hydrological theory (Sivapalan, 2005) as opposed to fine-scale process descriptions for individual catchments has occurred. One such emergent property is the hillslope- or catchment-scale threshold runoff response (e.g. Bonell, 1998; Weiler et al., 2005; Zehe et al., 2005; Lehmann et al., 2007), which is the critical point in time or space at which runoff behaviour rapidly changes (Phillips, 2006). In describing threshold driven systems, we have recognized that the simplicity of overall emergent catchment response is likely to be the result of interactions and feedbacks between processes that we do not fully understand. The use of thresholds as effective diagnostic tools of catchment behaviour has however been hindered by the fact that knowledge gained over different sites stand as disparate cases with no unifying theory to connect them. In this commentary, we build upon discussions from the AGU 2011 Fall Meeting session ‘Moving Towards a Unified Threshold-based Hydrological Theory’ to propose a new unifying hydrological research framework based on nonlinear threshold theory. It is not the goal of this commentary to summarize each of the presentations from the AGU session; rather, we discuss several of the central topics that emerged as the session progressed. These topics include: (1) defining a set of organizing principles for a threshold-based framework, (2) assessing the measurement-related hurdles we face on the road towards a threshold-based theory, and (3) encouraging both inductive and deductive methods to examine threshold behaviours in community-level experiments across sites.

Recommended citation: Genevieve Ali, Claire Oswald, Christopher Spence, Erik Cammeraat, Kevin McGuire, Thomas Meixner, Sim Reaney, "Towards a unified threshold-based hydrological theory: necessary components and recurring challenges." HYDROLOGICAL PROCESSES, 2013.

Integrated environmental modeling: A vision and roadmap for the future

Published in ENVIRONMENTAL MODELLING & SOFTWARE, 2013

“Integrated environmental modeling (IEM) is inspired by modern environmental problems, decisions, and policies and enabled by transdisciplinary science and computer capabilities that allow the environment to be considered in a holistic way. The problems are characterized by the extent of the environmental system involved, dynamic and interdependent nature of stressors and their impacts, diversity of stakeholders, and integration of social, economic, and environmental considerations. IEM provides a science-based structure to develop and organize relevant knowledge and information and apply it to explain, explore, and predict the behavior of environmental systems in response to human and natural sources of stress. During the past several years a number of workshops were held that brought IEM practitioners together to share experiences and discuss future needs and directions. In this paper we organize and present the results of these discussions. IEM is presented as a landscape containing four interdependent elements: applications, science, technology, and community. The elements are described from the perspective of their role in the landscape, current practices, and challenges that must be addressed. Workshop participants envision a global scale IEM community that leverages modern technologies to streamline the movement of science-based knowledge from its sources in research, through its organization into databases and models, to its integration and application for problem solving purposes. Achieving this vision will require that the global community of IEM stakeholders transcend social, and organizational boundaries and pursue greater levels of collaboration. Among the highest priorities for community action are the development of standards for publishing IEM data and models in forms suitable for automated discovery, access, and integration: education of the next generation of environmental stakeholders, with a focus on transdisciplinary research, development, and decision making: and providing a web-based platform for community interactions (e.g., continuous virtual workshops). Published by Elsevier Ltd..”

Recommended citation: Gerard Laniak, Gabriel Olchin, Jonathan Goodall, Alexey Voinov, Mary Hill, Pierre Glynn, Gene Whelan, Gary Geller, Nigel Quinn, Michiel Blind, Scott Peckham, Sim Reaney, Noha Gaber, Robert Kennedy, Andrew Hughes, "Integrated environmental modeling: A vision and roadmap for the future." ENVIRONMENTAL MODELLING &amp; SOFTWARE, 2013.

Concepts of hydrological connectivity: Research approaches, pathways and future agendas

Published in EARTH-SCIENCE REVIEWS, 2013

“For effective catchment management and intervention in hydrological systems a process-based understanding of hydrological connectivity is required so that: i) conceptual rather than solely empirical understanding drives how systems are interpreted; and ii) there is an understanding of how continuous flow fields develop under different sets of environmental conditions to enable managers to know when, where and how to intervene in catchment processes successfully. In order to direct future research into process-based hydrological connectivity this paper: i) evaluates the extent to which different concepts of hydrological connectivity have emerged from different approaches to measure and predict flow in different environments; ii) discusses the extent to which these different concepts are mutually compatible; and iii) assesses further research to contribute to a unified understanding of hydrological processes. Existing research is categorised into five different approaches to investigating hydrological connectivity: i) evaluating soil moisture patterns (soil moisture connectivity); ii) understanding runoff patterns and processes on hillslopes (flow-process connectivity); iii) investigating topographic controls (terrain-connectivity) including the impact of road networks on hydrological connectivity and catchment runoff; iv) developing models to explore and predict hydrological connectivity; and v) developing indices of hydrological connectivity. Analysis of published research suggests a relationship between research group, approach, geographic setting and the interpretation of hydrological connectivity. For further understanding of hydrological connectivity our knowledge needs to be developed using a range of techniques and approaches, there should be common understandings between researchers approaching the concept from different perspectives, and these meanings need to be communicated effectively with those responsible for land management. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved..”

Recommended citation: L. Bracken, J. Wainwright, G. Ali, D. Tetzlaff, M. Smith, S. Reaney, A. Roy, "Concepts of hydrological connectivity: Research approaches, pathways and future agendas." EARTH-SCIENCE REVIEWS, 2013.

Climate change and health and social care: Defining future hazard, vulnerability and risk for infrastructure systems supporting older people's health care in England

Published in APPLIED GEOGRAPHY, 2012

“Health and social care systems (including the care needs of the population and infrastructures providing health and social care) are likely to be influenced by climate change, in particular by the increasing frequency and severity of weather-related hazards such as floods and heatwaves. Coldwaves will also continue to be challenging in the foreseeable future. Protecting people's health and wellbeing from the impacts of climate change is especially important for older people, as they are particularly vulnerable to climate-related hazards. In addition, the proportion of people aged 65 and over is projected to increase significantly. This paper addresses these issues through a discussion of our work to map variations across England in future hazards, vulnerability and risk. We explain how this mapping has been used to identify areas of the country where the built infrastructure serving the older age group might be most severely impacted by climate-related events over the next 20-30 years and where planning for adaptation and resilience is most urgently required. Based on a review of research on the links between extreme weather events and their impacts on older people's health and the care services on which they depend, we developed operational definitions of extreme weather-related hazards likely to place particular pressure on health and social care systems that are essential for older people's health and wellbeing. We consider ways to relate these to the latest climate projections for the 2030s from the UK Climate Impacts Programme (UKCP09); river and coastal flooding projections for the 2050s from the 2004 UK Government's Foresight Flood and Coastal Defence Project (Environment Agency, 2004); and demographic projections for 2031 produced by the Office for National Statistics, UK. The research highlights the complexity of undertaking future hazard and vulnerability assessments. Key challenges include: how to define future hazards associated with climate change; how to predict and interpret future socio-demographic conditions contributing to vulnerability; and how geographical variability in hazards and vulnerabilities may combine to produce risks at the local level. In contrast to a number of more local studies which have focused on the vulnerability of urban populations to the impact of climate change (particularly heatwaves), the findings highlight the potential vulnerability of older populations in more rural regions (often in coastal areas) to a range of extreme weather-related hazards in both the North and South of England. (C) 2011 Elsevier Ltd. All rights reserved..”

Recommended citation: K. Oven, S. Curtis, S. Reaney, M. Riva, M. Stewart, R. Ohlemueller, C. Dunn, S. Nodwell, L. Dominelli, R. Holden, "Climate change and health and social care: Defining future hazard, vulnerability and risk for infrastructure systems supporting older people&apos;s health care in England." APPLIED GEOGRAPHY, 2012.

A Monte Carlo approach to the inverse problem of diffuse pollution risk in agricultural catchments

Published in SCIENCE OF THE TOTAL ENVIRONMENT, 2012

“The hydrological and biogeochemical processes that operate in catchments influence the ecological quality of freshwater systems through delivery of fine sediment, nutrients and organic matter. Most models that seek to characterise the delivery of diffuse pollutants from land to water are reductionist. The multitude of processes that are parameterised in such models to ensure generic applicability make them complex and difficult to test on available data. Here, we outline an alternative - data-driven - inverse approach. We apply SCIMAP, a parsimonious risk based model that has an explicit treatment of hydrological connectivity. we take a Bayesian approach to the inverse problem of determining the risk that must be assigned to different land uses in a catchment in order to explain the spatial patterns of measured in-stream nutrient concentrations. We apply the model to identify the key sources of nitrogen (N) and phosphorus (P) diffuse pollution risk in eleven UK catchments covering a range of landscapes. The model results show that: 1) some land use generates a consistently high or low risk of diffuse nutrient pollution; but 2) the risks associated with different land uses vary both between catchments and between nutrients; and 3) that the dominant sources of P and N risk in the catchment are often a function of the spatial configuration of land uses. Taken on a case-by-case basis, this type of inverse approach may be used to help prioritise the focus of interventions to reduce diffuse pollution risk for freshwater ecosystems. (C) 2012 Elsevier B.V. All rights reserved..”

Recommended citation: David Milledge, Stuart Lane, A. Heathwaite, Sim Reaney, "A Monte Carlo approach to the inverse problem of diffuse pollution risk in agricultural catchments." SCIENCE OF THE TOTAL ENVIRONMENT, 2012.

Using the nutrient transfer continuum concept to evaluate the European Union Nitrates Directive National Action Programme

Published in ENVIRONMENTAL SCIENCE & POLICY, 2011

“Agricultural catchments are where farm and landscape management interact with policy and science; especially with regard to the implementation and evaluation of agri-environmental regulation. The Nitrates Directive constrains nitrogen and phosphorus use and management on agricultural land across all EU member states and is one of the programmes of measures to mitigate eutrophication of water resources under the Water Framework Directive. All policies require a robust evaluation tool and for the potential diffuse transfer of nutrients from land to water, the nutrient transfer continuum concept is applied here as an example framework in small (6-30 km(2)) catchments. The experimental design, methods and some early results are presented: auditing nutrient sources to established levels of compliance is the first stage and considers nutrient use and soil status. Studying pathways provides an understanding of linkages between the land sources and delivery in catchment rivers. This delivery is generally associated with episodic, high magnitude transfers and may not necessarily be the only or even primary ecological impact in rivers. Critiquing existing delivery/impact metrics and defining appropriate standards for identifying trajectories associated with diffuse nutrient transfer will be important in ensuring that agri-environmental policies are given a fair and thorough evaluation over a suitable time period. (C) 2011 Elsevier Ltd. All rights reserved..”

Recommended citation: D. Wall, P. Jordan, A. Melland, P. Mellander, C. Buckley, S. Reaney, G. Shortie, "Using the nutrient transfer continuum concept to evaluate the European Union Nitrates Directive National Action Programme." ENVIRONMENTAL SCIENCE &amp; POLICY, 2011.

Risk-based modelling of diffuse land use impacts from rural landscapes upon salmonid fry abundance

Published in ECOLOGICAL MODELLING, 2011

“Research has demonstrated that landscape or watershed scale processes can influence instream aquatic ecosystems, in terms of the impacts of delivery of fine sediment, solutes and organic matter. Testing such impacts upon populations of organisms (i.e. at the catchment scale) has not proven straightforward and differences have emerged in the conclusions reached. This is: (1) partly because different studies have focused upon different scales of enquiry; but also (2) because the emphasis upon upstream land cover has rarely addressed the extent to which such land covers are hydrologically connected, and hence able to deliver diffuse pollution, to the drainage network However, there is a third issue. In order to develop suitable hydrological models, we need to conceptualise the process cascade. To do this, we need to know what matters to the organism being impacted by the hydrological system, such that we can identify which processes need to be modelled. Acquiring such knowledge is not easy, especially for organisms like fish that might occupy very different locations in the river over relatively short periods of time. However, and inevitably, hydrological modellers have started by building up piecemeal the aspects of the problem that we think matter to fish. Herein, we report two developments: (a) for the case of sediment associated diffuse pollution from agriculture, a risk-based modelling framework, SCIMAP, has been developed, which is distinct because it has an explicit focus upon hydrological connectivity; and (b) we use spatially distributed ecological data to infer the processes and the associated process parameters that matter to salmonid fry. We apply the model to spatially distributed salmon and fry data from the River Eden, Cumbria, England. The analysis shows, quite surprisingly, that arable land covers are relatively unimportant as drivers of fry abundance. What matters most is intensive pasture, a land cover that could be associated with a number of stressors on salmonid fry (e.g. pesticides, fine sediment) and which allows us to identify a series of risky field locations, where this land cover is readily connected to the river system by overland flow. (C) 2010 Elsevier B.V. All rights reserved..”

Recommended citation: Reaney S., Lane S., Heathwaite A. and Dugdale L., 2011: Risk-based modelling of diffuse land use impacts from rural landscapes upon salmonid fry abundance; ECOLOGICAL MODELLING, Volume 222, Issue 4, Pages 1016-1029; [https://doi.org/10.1016/j.ecolmodel.2010.08.022](https://doi.org/10.1016/j.ecolmodel.2010.08.022)

Representation of landscape hydrological connectivity using a topographically driven surface flow index

Published in WATER RESOURCES RESEARCH, 2009

“This paper assesses the extent to which a topographically defined description of the spatial arrangement of catchment wetness can be used to represent landscape hydrological connectivity in temperate river catchments. A physically based distributed hydrological model is used to characterize the space-time patterns of surface overland flow connection to the drainage network. These characterizations are compared with a static descriptor of the spatial structure of topographically controlled local wetness, called here the Network Index. Theoretically, if topography is the primary control upon hydrological response, the level of catchment wetness required to maintain connectivity along a flow path should be greater for flow paths that have a lower value of the topographically controlled local wetness. We find that our static descriptor can be used to generalize a significant proportion of the time-averaged spatial variability in connectivity, in terms of both the propensity to and duration of connection. Although the extent to which this finding holds will vary with the extent of topographic control of hydrological response, in catchments with relatively shallow soils and impervious geology our index could improve significantly the estimation of the transfer of sediment and dissolved materials to the drainage network and so assist with both diffuse pollution and climate change impact studies. The work also provides a second reason for the concept that there are Critical Source Areas in river catchments: these arise from the extent to which that material can be delivered to the drainage network, as well as the generation of risky material itself.”

Recommended citation: S. Lane, S. Reaney, A. Heathwaite 2009, Representation of landscape hydrological connectivity using a topographically driven surface flow index; WATER RESOURCES RESEARCH, 2009. Volume 45, Issue 8 https://doi.org/10.1029/2008WR007336

The use of agent based modelling techniques in hydrology: determining the spatial and temporal origin of channel flow in semi-arid catchments

Published in EARTH SURFACE PROCESSES AND LANDFORMS, 2008

“Information on the spatial and temporal origin of runoff entering the channel during a storm event would be valuable in understanding the physical dynamics of catchment hydrology; this knowledge could be used to help design flood defences and diffuse pollution mitigation strategies. The majority of distributed hydrological models give information on the amount of flow leaving a catchment and the pattern of fluxes within the catchment. However, these models do not give any precise information on the origin of runoff within the catchment. The spatial and temporal distribution of runoff sources is particularly intricate in semi-arid catchments, where there are complex interactions between runoff generation, transmission and re-infiltration over short temporal scales. Agents are software components that are capable of moving through and responding to their local environment. In this application, the agents trace the path taken by water through the catchment. They have information on their local environment and on the basis of this information make decisions on where to move. Within a given model iteration, the agents are able to stay in the current cell, infiltrate into the soil or flow into a neighbouring cell. The information on the current state of the hydrological environment is provided by the environment generator. In this application, the Connectivity of Runoff Model (CRUM) has been used to generate the environment. CRUM is a physically based, distributed, dynamic hydrology model, which considers the hydrological processes relevant for a semi-arid environment at the temporal scale of a single storm event. During the storm event, agents are introduced into the model across the catchment; they trace the flows of water and store information on the flow pathways. Therefore, this modelling approach is capable of giving a novel picture of the temporal and spatial dynamics of flow generation and transmission during a storm event. This is possible by extracting the pathways taken by the agents at different time slices during the storm. The agent based modelling approach has been applied to two small catchments in South East Spain. The modelling approach showed that the two catchments responded differently to the same rainfall event due to the differences in the runoff generation and overland flow connectivity between the two catchments. The model also showed that the time of travel to the nearest flow concentration is extremely important for determining the connectivity of a point in the landscape with the catchment outflow. Copyright (C) 2007 John Wiley & Sons, Ltd..”

Recommended citation: S. Reaney, "The use of agent based modelling techniques in hydrology: determining the spatial and temporal origin of channel flow in semi-arid catchments." EARTH SURFACE PROCESSES AND LANDFORMS, 2008.

Use of the Connectivity of Runoff Model (CRUM) to investigate the influence of storm characteristics on runoff generation and connectivity in semi-arid areas

Published in HYDROLOGICAL PROCESSES, 2007

“Much attention has been given to the surface controls on the generation and transmission of runoff in semi-arid areas. However, the surface controls form only one part of the system; hence, it is important to consider the effect that the characteristics of the storm event have on the generation of runoff and the transmission of flow across the slope. The impact of storm characteristics has been investigated using the Connectivity of Runoff Model (CRUM). This is a distributed, dynamic hydrology model that considers the hydrological processes relevant to semi-arid environments at the temporal scale of a single storm event. The key storm characteristics that have been investigated are the storm duration, rainfall intensity, rainfall variability and temporal structure. This has been achieved through the use of a series of defined storm hydrographs and stochastic rainfall. Results show that the temporal fragmentation of high-intensity rainfall is important for determining the travel distances of overland flow and, hence, the amount of runoff that leaves the slope as discharge. If the high-intensity rainfall is fragmented, then the runoff infiltrates a short distance downslope. Longer periods of high-intensity rainfall allow the runoff to travel further and, hence, become discharge. Therefore, storms with similar amounts of high-intensity rainfall can produce very different amounts of discharge depending on the storm characteristics. The response of the hydrological system to changes in the rainfall characteristics can be explained using a four-stage model of the runoff generation process. These stages are: (1) all water infiltrating, (2) the surface depression store filling or emptying without runoff occurring, (3) the generation and transmission of runoff and (4) the transmission of runoff without new runoff being generated. The storm event will move the system between the four stages and the nature of the rainfall required to move between the stages is determined by the surface characteristics. This research shows the importance of the variable-intensity rainfall when modelling semi-arid runoff generation. The amount of discharge may be greater or less than the amount that would have been produced if constant rainfall intensity is used in the model. Copyright (c) 2006 John Wiley & Sons, Ltd..”

Recommended citation: Reaney, S.M., Bracken, L.J. and Kirkby, M.J. (2007), Use of the Connectivity of Runoff Model (CRUM) to investigate the influence of storm characteristics on runoff generation and connectivity in semi-arid areas. Hydrol. Process., 21: 894-906. https://doi.org/10.1002/hyp.6281

Surveillant science: Challenges for the management of rural environments emerging from the new generation diffuse pollution models

Published in JOURNAL OF AGRICULTURAL ECONOMICS, 2006

“Current models of diffuse pollution are characterised by a progressive engagement with remotely-sensed data coupled with more elegant modelling approaches. Central to these new models is the concept of connectivity, which leads to the identification and prioritisation of those landscape units (e.g., fields) where the consequences of land management activities are most readily transmitted to watercourses. The practice of diffuse pollution modelling using such models encounters certain problems. Following Brewer we argue that interdisciplinarity offers the opportunity to overcome these problems through: (1) its explicit recognition of the framing implicit in model development; (2) an emphasis on context in problem-solving; (3) methodological pluralism; and (4) following from these other factors, the possibility of a different sort of engagement between land managers and modellers. Hence, the case for developing interdisciplinary approaches goes beyond the conventional dictates of problem-led research and points to very different ways of conducting diffuse pollution research, taking on board the full dimensions of interdisciplinarity, with its emphasis on reflexivity, contextuality, substance and engagement..”

Recommended citation: SN Lane, CJ Brookes, AL Heathwaite, S Reaney, "Surveillant science: Challenges for the management of rural environments emerging from the new generation diffuse pollution models." JOURNAL OF AGRICULTURAL ECONOMICS, 2006.

The influence of land use, soils and topography on the delivery of hillslope runoff to channels in SE Spain

Published in EARTH SURFACE PROCESSES AND LANDFORMS, 2002

“It is generally accepted that within particular physiographic and climatic regions catchments exhibit differences in their hydrological response. These differences result from the interaction of spatial variability in catchment characteristics, variability of rainfall inputs and surface and subsurface hydrological processes. These interactions are complex and difficult to unravel. Hydrologically similar surfaces (HYSS) have been used to identify catchment areas that have a similar response to rainfall and have been identified at a number of scales. HYSS have been identified at the subcatchment scale for the Rambla de Nogalte in SE Spain. Areas with similar at-a-point hydrological storages were distinguished by using a combination of geology, land use and topography. This mapping was compared with discharge estimates made throughout the catchment following a seven-year return interval flood in September 1997. From this significant flood source areas were identified from reaches showing rapidly increasing channel discharge, and associated with HYSS that combined suitable internal characteristics with good connectivity to the main channel. This paper presents a simulation model that has been developed to investigate the way in which the hydrological response of areas within a HYSS respond to changes in source area, gradient, connectivity to the channel, storm size and intensity profile. This is one of the first studies using a hillslope model to investigate spatial patterns of runoff-response in semi-arid areas and results have implications for scaling up hydrological response, and on how the dynamics of runoff producing areas vary both underchanging storm conditions and over time. It is implicit in our results that the nature of stream-slope coupling differs substantively between semi-arid and humid areas. Copyright (C) 2002 John Wiley Sons, Ltd..”

Recommended citation: M Kirkby, L Bracken, S Reaney, "The influence of land use, soils and topography on the delivery of hillslope runoff to channels in SE Spain." EARTH SURFACE PROCESSES AND LANDFORMS, 2002.