O’Hanley, J., Pompeu, P., Louzada, M., Zambaldi, L. and Kemp, P. (2020). Optimizing hydropower dam location and removal in the São Francisco River basin, Brazil to balance hydropower and river biodiversity tradeoffs. Landscape and Urban Planning [Online] 195:103725. Available at: https://doi.org/10.1016/j.landurbplan.2019.103725.
To support eco-friendly hydropower planning in developing regions, we propose a spatial optimization model for locating dams to balance tradeoffs between hydropower generation and migratory fish species richness. Our model incorporates two special features. First, it is tailored to the dispersal of tropical migratory fishes, which require long, unimpeded river stretches to complete their life-cycle. To model fish with this type of dispersal pattern, we introduce the concept of a river pathway, which represents a novel way to describe river connectivity. Second, it combines decisions about dam placement and removal, thus facilitating opportunities for hydropower offsetting. We apply our model to the São Francisco River basin, Brazil, an area of hydropower-freshwater biodiversity conflict. We find that dams have reduced weighted migratory fish richness 51% compared to a pre-dam baseline. We also find that even limited dam removal has the potential to significantly enhance fish biodiversity. Offsetting the removal of a single dam by the optimal siting of new dams could increase fish richness by 25% above the current average. Moving forward, optimizing new dam sites to increase hydropower by 20%, rather than selecting the fewest number of dams, could reduce fish species losses by 89%. If decisions about locating new dams are combined with dam removal, then a win-win can even be achieved with 20% greater hydropower and 19% higher species richness. Regardless of hydropower targets and dam removal options, a key observation is that optimal sites for dams are mostly located in the upper reaches of the basin rather than along the main stem of the São Francisco River or its main tributaries.
Preston, G., Horne, P., Scaparra, M. and O’Hanley, J. (2020). Masterplanning at the Port of Dover: The Use of Discrete-Event Simulation in Managing Road Traffic. Sustainability [Online] 12:1067. Available at: http://dx.doi.org/10.3390/su12031067.
The Port of Dover is Europe’s busiest ferry port, handling £119 billion or 17% of the UK’s annual trade in goods. The Port is constrained geographically to a small area and faces multiple challenges, both short- and long-term, with managing the flow of five million vehicles per year to/from mainland Europe. This article describes some of the work that the Port is doing to minimize the impact of port road traffic on the local community and environment using discrete-event simulation modeling. Modeling is particularly valuable in identifying where future bottlenecks are likely to form within the Port due to projected growth in freight traffic and comparing the effectiveness of different interventions to cope with growth. One of our key findings is that space which can be used flexibly is far more valuable than dedicated space. This is supported by the much greater reduction in traffic congestion that is expected to be achieved given a 10% increase in freight traffic by reallocating space at the front of the system to temporarily hold vehicles waiting to pass through border control and check-in compared to extending the amount of space for ferry embarkation at the rear of the system. The importance of flexible space has implications for port design that can be applied more broadly. Modeling is also useful in identifying critical thresholds for vehicle processing times that would cause the system to become overwhelmed. Increasing the check-in time by just three to five minutes, for example, would completely exceed the Port’s capacity and produce indefinite queueing. This finding has important implications for Brexit planning. From a wider context, the research presented here nicely illustrates how simulation can be used to instill more evidence-based thinking into port masterplanning and support “green port” and other corporate sustainability initiatives.
Jones, W., Kotiadis, K., Scaparra, M. and O’Hanley, J. (2020). Using Simulation to Improve the Customer Experience at Eurostar. Impact [Online] 2020:7-11. Available at: https://doi.org/10.1080/2058802X.2019.1703346.
Malik, S., Fearne, A. and O’Hanley, J. (2019). The use of disaggregated demand information to improve forecasts and stock allocation during sales promotions: a simulation and optimisation study using supermarket loyalty card data. International Journal of Value Chain Management [Online] 10:339-357. Available at: http://dx.doi.org/10.1504/IJVCM.2019.103271.
Our work highlights the importance of using disaggregated demand information at store level to improve sales forecasts and stock allocation during sales promotions. Monte Carlo simulation and optimisation modelling were used to estimate short-term promotional impacts. Supermarket loyalty card data was used from a major UK retailer to identify the benefits of using disaggregated demand data for improved forecasting and stock allocation. The results suggest that there is a high degree of heterogeneity in demand at individual store level due to number of factors including the weather, the characteristics of shoppers, the characteristics of products and store format, all of which conspire to generate significant variation in promotional uplifts. The paper is the first to use supermarket loyalty card data to generate store level promotional forecasts and quantify the benefits of disaggregating the allocation of promotional stock to the level of individual stores rather than regional distribution centres.
Ioannidou, C. and O’Hanley, J. (2019). The Importance of Spatiotemporal Fish Population Dynamics in Barrier Mitigation Planning. Biological Conservation [Online] 231:67-76. Available at: https://dx.doi.org/10.1016/j.biocon.2019.01.001.
In this study, we propose a novel framework combining spatially explicit population viability analysis and optimization for prioritizing fish passage barrier mitigation decisions. Our model aims to maximize the equilibrium population size, or alternatively minimize the extinction risk, of a target fish species
subject to a budget on the total cost of barrier mitigation. A case study involving a wild coho salmon (Oncorhynchus kisutch) population from the Tillamook basin, Oregon, USA is used to illustrate the benefits of our approach. We consider two different spawning adult dispersal patterns, river and reach level homing, as well as straying. Under density dependent population growth, we find that homing behavior type has a significant effect on barrier mitigation decisions. In particular, with reach homing, our model produces virtually the same population sizes as a more traditional barrier prioritization procedure designed to maximize accessible habitat. With river homing, however, we find that it is not necessary to remove all barriers in order to maximize equilibrium population size. Indeed, a stochastic version of our model reveals that removing all barriers actually results in a marginal increase in quasi-extinction risk. We hypothesize that this is due to a population thinning effect of barriers, resulting in a surplus of recruits in areas of low spawner density. Our findings highlights the importance of considering spatiotemporal fish population dynamics in river connectivity restoration planning. By adding greater biological realism, models such as ours can help conservation managers to more strategically allocate limited resources, resulting in both cost savings and improved population status for a focal species.
Neeson, T., Moody, A., O’Hanley, J., Diebel, M., Doran, P., Ferris, M., Colling, T. and McIntyre, P. (2018). Aging infrastructure creates opportunities for cost-efficient restoration of aquatic ecosystem connectivity. Ecological Applications [Online] 28:1494-1502. Available at: https://doi.org/10.1002/eap.1750.
A hallmark of industrialization is the construction of dams for water management and roads for transportation, leading to fragmentation of aquatic ecosystems. Many nations are striving to address both maintenance backlogs and mitigation of environmental impacts as their infrastructure ages. Here, we test whether accounting for road repair needs could offer opportunities to boost conservation efficiency by piggybacking connectivity restoration projects on infrastructure maintenance. Using optimization models to align fish passage restoration sites with likely road repair priorities, we find potential increases in conservation return-on-investment ranging from 17% to 25%. Importantly, these gains occur without compromising infrastructure or conservation priorities; simply communicating openly about objectives and candidate sites enables greater accomplishment at current funding levels. Society embraces both reliable roads and thriving fisheries, so overcoming this coordination challenge should be feasible. Given deferred maintenance crises for many types of infrastructure, there could be widespread opportunities to enhance the cost-effectiveness of conservation investments by coordinating with infrastructure renewal efforts.
Milt, A., Diebel, M., Doran, P., Ferris, M., Herbert, M., Khoury, M., Moody, A., Neeson, T., Ross, J., Treska, T., O’Hanley, J., Walter, L., Wangen, S., Yacobson, E. and McIntyre, P. (2018). Minimizing opportunity costs to aquatic connectivity restoration while controlling an invasive species. Conservation Biology [Online] 32:894-904. Available at: https://doi.org/10.1111/cobi.13105.
Controlling invasive species is critical for conservation but can have unintended consequences for native species and divert resources away from other efforts. This dilemma occurs on a grand scale in the North American Great Lakes, where dams and culverts block tributary habitat access for desirable fish species and are also a lynchpin of long-standing efforts to limit ecological damage inflicted by invasive, parasitic sea lamprey. Habitat restoration and sea lamprey control create conflicting goals for managing aging infrastructure. Here, we use optimization to minimize opportunity costs to habitat gains for 37 desirable migratory
fishes that arise from restricting sea lamprey access (0-25% increase) when selecting barriers for removal under a limited budget ($1-105M). Imposing limits on sea lamprey habitat reduces gains in tributary access for desirable species by 15-50% relative to an unconstrained scenario. Working around a sea lamprey access cap is costly for 30 of 37 species (e.g., an additional $20-80M for lake sturgeon), and often requires ≥5% increase in sea lamprey access to be feasible. Narrowly distributed species exhibit the highest opportunity costs, but also benefit more at lower cost from allowing small increases in sea lamprey access. Our results illustrate the value of optimization for limiting opportunity costs when balancing invasion control against restoration benefits for diverse desirable species.
Such tradeoff analyses are essential for expanded efforts in the conservation community to restore connectivity within fragmented rivers without unleashing invaders.
Erős, T., O’Hanley, J. and Czeglédi, I. (2018). A Unified Model for Optimizing Riverscape Conservation. Journal of Applied Ecology [Online] 55:1871-1883. Available at: http://dx.doi.org/10.1111/1365-2664.13142.
1. Spatial prioritization tools provide a means of finding efficient trade-offs between biodiversity protection and the delivery of ecosystem services. Although a large number of prioritization approaches have been proposed, most are specifically designed for terrestrial systems. When applied to river ecosystems, they often fail to adequately account for the essential role that landscape connectivity plays in maintaining both biodiversity and ecosystem services. This is particularly true of longitudinal connectivity, which in many river catchments is highly altered by the presence of dams, stream-road crossings, and other artificial structures.
2. We propose a novel framework for coordinating river conservation and connectivity restoration. We formulate an optimization model for deciding which subcatchments to designate for ecosystem services and which to include in a river protected area (RPA) network, while also deciding which existing river barriers to remove in order to maximize longitudinal connectivity within the RPA network. In addition to constraints on the size and makeup of the RPA network, the model also considers the suitability of sites for conservation, based on a biological integrity index, and connectivity to multiple habitat types. We demonstrate the usefulness of our approach using a case study involving four managed river catchments located in Hungary.
3. Results show that large increases in connectivity-weighted habitat can be achieved through targeted selection of barrier removals and that the benefits of barrier removal are strongly depend on RPA network size. We find that (i) highly suboptimal solutions are produced if habitat conservation planning and connectivity restoration are done separately and (ii) RPA acquisition provides substantially greater marginal benefits than barrier removal given limited resources.
4. Synthesis and applications. Finding a balance between conservation and ecosystem services provision should give more consideration to connectivity restoration planning, especially in multi-use riverscapes. We present the first modelling framework to directly integrate and optimize river conservation and connectivity restoration planning. This framework can help conservation managers to better account for connectivity, resulting in more effective catchment scale maintenance of biological integrity and ecosystem services delivery.
Traffic Modelling at the Port of Dover (2018). Impact [Online] 2018:7-11. Available at: https://doi.org/10.1080/2058802X.2018.1452422.
The port of Dover has undergone many reincarnations over the centuries: from a fortified port complete with lighthouse in the first century AD, to a military Cinque Port in the middle ages, to the ferry and hovercraft terminal of the late twentieth century. Dover’s principal role now is as a Roll-on, Roll-off (Ro-Ro) Ferry Terminal, in which 2 ferry companies (P&O and DFDS) between them make up to 60 round trips a day to the French Ports of Calais and Dunkerque. They carry over 2.6 million lorries, 2 million cars, and 12 million people a year. The economic value in goods handled through the Port is up to 17% of the UK’s overall trade in goods. Based on 2016 projections, freight traffic is expected to increase by up to 40% in the next 30 years. However, the Dover Eastern Docks Ferry Terminal is small, around half a square kilometre, and expansion is challenging since it is hemmed in by the sea, the White Cliffs of Dover, and Dover town.
A dynamic model for road protection against flooding (2017). Journal of the Operational Research Society [Online] 68:74-88. Available at: http://dx.doi.org/10.1057/s41274-016-0019-0.
This paper focuses on the problem of identifying optimal protection strategies to reduce the impact of flooding on a road network. We propose a dynamic mixed-integer programming model that extends the classic concept of road network protection by shifting away from single-arc fortifications to a more general and realistic approach involving protection plans that cover multiple components. We also consider multiple disruption scenarios of varying magnitude. To efficiently solve large problem instances, we introduce a customised GRASP heuristic. Finally, we provide some analysis and insights from a case study of the Hertfordshire road network in the East of England. Results show that optimal protection strategies mainly involve safeguarding against flooding events that are small and likely to occur, whereas implementing higher protection standards are not considered cost-effective.
Tran, T., Scaparra, M. and O’Hanley, J. (2017). A Hypergraph Multi-Exchange Heuristic for the Single-Source Capacitated Facility Location Problem. European Journal of Operational Research [Online] 263:173-187. Available at: http://dx.doi.org/10.1016/j.ejor.2017.04.032.
In this paper, we introduce a large-scale neighborhood search procedure for solving the single-source capacitated facility location problem (SSCFLP). The neighborhood structures are induced by innovative split multi-customer multi-exchanges, where clusters of customers assigned to one facility can be moved simultaneously to multiple destination facilities and vice versa. To represent these exchanges, we use two types of improvement hypergraphs. The improvement hypergraphs are built dynamically and the moving customers associated with each hyperedge are selected by solving heuristically a suitably defined mixed-integer program. We develop a hypergraph search framework, including forward and backward procedures, to identify improving solutions efficiently. Our proposed algorithm can obtain improving moves more quickly and even find better solutions than a traditional multi-exchange heuristic (Ahuja et al., 2004). In addition, when compared with the Kernel Search algorithm (Guastaroba and Speranza, 2014), which at present is the most effective for solving SSCFLP, our algorithm is not only competitive but can find better solutions or even the best known solution to some very large scale benchmark instances from the literature.
Mingers, J., O’Hanley, J. and Okunola, M. (2017). Using Google Scholar Institutional Level Data to Evaluate the Quality of University Research. Scientometrics [Online] 113:1627-1643. Available at: http://dx.doi.org/10.1007/s11192-017-2532-6.
In recent years, the extent of formal research evaluation, at all levels from the individual to the multiversity has increased dramatically. At the institutional level, there are world university rankings based on an ad hoc combination of different indicators. There are also national exercises, such as those in the UK and Australia that evaluate research outputs and environment through peer review panels. These are extremely costly and time consuming. This paper evaluates the possibility of using Google Scholar (GS) institutional level data to evaluate university research in a relatively automatic way. Several citation-based metrics are collected from GS for all 130 UK universities. These are used to evaluate performance and produce university rankings which are then compared with various rankings based on the 2014 UK Research Excellence Framework (REF). The rankings are shown to be credible and to avoid some of the obvious problems of the REF ranking, as well as being highly efficient and cost effective. We also investigate the possibility of normalizing the results for the university subject mix since science subjects generally produce significantly more citations than social science or humanities.
Sethi, S., O’Hanley, J., Gerken, J., Ashline, J. and Bradley, C. (2017). High value of ecological information for river connectivity restoration. Landscape Ecology [Online] 32:2327-2336. Available at: http://dx.doi.org/10.1007/s10980-017-0571-2.
Context: Efficient restoration of longitudinal river connectivity relies on barrier mitigation prioritization tools that incorporate stream network spatial structure to maximize ecological benefits given limited resources. Typically, ecological bene 5 fits of barrier mitigation are measured using proxies such as the amount of accessible riverine habitat. Objectives We developed an optimization approach for barrier mitigation planning which directly incorporates the ecology of managed taxa, and applied it to an urbanizing salmonbearing watershed in Alaska.
Methods: A novel river connectivity metric that exploits information on the distribution and movement of managed taxon was embedded into a barrier prioritization framework to identify optimal mitigation actions given limited restoration budgets. The value of ecological information on managed taxa was estimated by comparing costs to achieve restoration targets across alternative barrier prioritization approaches.
Results: Barrier mitigation solutions informed by life history information outperformed those using only river connectivity proxies, demonstrating high value of ecological information for watershed restoration. In our study area, information on salmon ecology was typically valued at 0.8-1.2M USD in costs savings to achieve a given benefit level relative to solutions derived only from stream network information, equating to 16-28% of the restoration budget. Conclusions Investing in ecological studies may achieve win-win outcomes of improved understanding of aquatic ecology and greater watershed restoration efficiency.
Moody, A., Neeson, T., Milt, A., Wangen, S., Dischler, J., Diebel, M., Herbert, M., Khoury, M., Yacobson, E., Doran, P., Ferris, M., O’Hanley, J. and McIntyre, P. (2017). Pet Project or Best Project? Online Decision Support Tools for Prioritizing Barrier Removals in the Great Lakes and Beyond. Fisheries [Online] 42:57-65. Available at: http://dx.doi.org/10.1080/03632415.2016.1263195.
Structures that block movement of fish through river networks are built to serve a variety of societal needs, including transportation, hydroelectric power, and exclusion of exotic species. Due to their abundance, road crossings and dams reduce the amount of habitat available to fish that migrate from the sea or lakes into rivers to breed. The benefits to fish of removing any particular barrier depends on its location within the river network, its passability to fish, and the relative position of other barriers within the network. Balancing the trade-offs between ecological and societal values makes choosing among potential removal projects difficult. To facilitate prioritization of barrier removals, we developed an online decision support tool (DST) with three functions: (1) view existing barriers at various spatial scales; (2) modify information about barriers, including removal costs; and (3) run optimization models to identify portfolios of removals that provide the greatest amount of habitat access for a given budget. A survey of available DSTs addressing barrier removal prioritization indicates that barrier visualization is becoming widespread but few tools allow dynamic calculation of connectivity metrics, scenario analysis, or optimization. Having these additional functions, our DST enables organizations to develop barrier removal priorities based on
cost-effectiveness in restoring aquatic connectivity.
Fraser, I. and O’Hanley, J. (2016). Benefits Transfer and the Aquatic Environment: An Investigation into the Context of Fish Passage Improvement. Journal of Environmental Management [Online] 183:1079-1087. Available at: http://dx.doi.org/10.1016/j.jenvman.2016.09.041.
We present findings from a choice experiment investigating improvements in the aquatic environment from mitigation of barriers to fish passage. Implemented at a local and national level, results reveal positive preferences for increased numbers of fish species as well as fish abundance. In addition, we examine if in this case the willingness to pay estimates are suitable for direct transfer between national and local settings. For both samples, we consider the extent to which stated attribute non-attendance impacts estimates of willingness to pay and the potential ability of researchers to transfer values between contexts. Implications of the use of benefit transfer within this policy context are discussed in light of our findings.
Tran, T., O’Hanley, J. and Scaparra, M. (2016). Reliable hub network design: Formulation and solution techniques. Transportation Science [Online] 51:358-375. Available at: http://dx.doi.org/10.1287/trsc.2016.0679.
In this paper, we investigate the issue of unreliability in hub location planning. A mixed integer nonlinear programming model is formulated for optimally locating p uncapacitated hubs, each of which can fail with a site-specific probability. The objective is to determine the location of hubs and the assignment of demand nodes to hubs in order to minimize expected demand weighted travel cost plus a penalty if all hubs fail. A linear version of the model is developed employing a specialized flow network called a probability lattice to evaluate compound probability terms. A Tabu search algorithm is proposed to find optimal to near optimal solutions for large problem instances. A parallel computing strategy is integrated into the Tabu search process to improve performance. Experimental results carried out on several benchmark instances show the efficiency of our linearized model and heuristic algorithm. Compared to a standard hub median model that disregards the potential for hub failures, our model produces solutions that serve larger numbers of customers and at lower cost per customer.
Ioannidou, C. and O’Hanley, J. (2016). Eco-friendly location of small hydropower. European Journal of Operational Research [Online] 264:907-918. Available at: http://dx.doi.org/10.1016/j.ejor.2016.06.067.
We address the problem of locating small hydropower dams in an environmentally friendly manner. We propose the use of a multi-objective optimization model to maximize total hydropower production, while limiting negative impacts on river connectivity. Critically, we consider the so called “backwater effects” that dams have on power generation at nearby upstream sites via changes in water surface profiles. We further account for the likelihood that migratory fish and other aquatic species can successfully pass hydropower dams and other artificial/natural barriers and how this is influenced by backwater effects. Although naturally represented in nonlinear form, we manage through a series of linearization steps to formulate a mixed integer linear programing model. We illustrate the utility of our proposed framework using a case study from England and Wales. Interestingly, we show that for England and Wales, a region heavily impacted by a large number of existing river barriers, that installation of small hydropower dams fitted with even moderately effective fish passes can, in fact, create a win-win situation that results in increased hydropower and improved river connectivity.
King, S., O’Hanley, J., Newbold, L., Kemp, P. and Diebel, M. (2016). A toolkit for optimizing fish passage barrier mitigation actions. Journal of Applied Ecology [Online] 54:599-611. Available at: http://dx.doi.org/10.1111/1365-2664.12706.
1. The presence of dams, stream–road crossings and other infrastructure often compromises the connectivity of rivers, leading to reduced fish abundance and diversity. The assessment and mitigation of river barriers is critical to the success of restoration efforts aimed at restoring river integrity.
2. In this study, we present a combined modelling approach involving statistical regression methods and mixed integer linear programming to maximize resident fish species richness within a catchment through targeted barrier mitigation. Compared to existing approaches, our proposed method provides enhanced biological realism while avoiding the use of complex and computationally intensive population/ecosystem models.
3. To estimate barrier passability quickly and at low cost, we further outline a rapid barrier assessment methodology. The methodology is used to characterize potential passage barriers for various fish species common to the UK but can be readily adapted to different planning areas and other species of interest.
4. We demonstrate the applicability of our barrier assessment and prioritization approach based on a case study of the River Wey, located in south-east England. We find that significant increases in species richness can be achieved for modest investment in barrier mitigation. In particular, dams and weirs with low passability located on mid- to high-order streams are identified as top priorities for mitigation.
5. Synthesis and applications. Our study shows the benefits of combining a coarse resolution barrier assessment methodology with state-of-the-art optimization modelling to cost-effectively plan fish passage barrier mitigation actions. The modelling approach can help inform on-the-ground river restoration decision-making by providing a recommended course of action that best allocates limited resources in order to restore longitudinal connectivity and maximize ecological gains.
Diebel, M., Fedora, M., Cogswell, S. and O’Hanley, J. (2015). Effects of road crossings on habitat connectivity for stream-resident fish. River Research and Applications 31:1251-1261.
Road crossings can act as barriers to the movement of stream fishes, resulting in habitat fragmentation, reduced population resilience to environmental disturbance and higher risks of extinction. Strategic barrier removal has the potential to improve connectivity in stream networks, but managers lack a consistent framework for determining which projects will most benefit target species. The objective of this study is to develop a method for identifying and prioritizing action on road crossings in order to restore stream network connectivity. We demonstrate the method using a case study from the Pine-Popple watershed in Wisconsin. First, we propose a new metric for quantifying stream connectivity status for stream-resident fish. The metric quantifies the individual and cumulative effects of barriers on reach and watershed level connectivity, while accounting for natural barriers, distance-based dispersal limitations and variation in habitat type and quality. We conducted a comprehensive field survey of road crossings in the watershed to identify barriers and estimate replacement costs. Of the 190 surveyed road crossings, 74% were determined to be barriers to the movement of at least one species or life stage of fish, primarily due to high water velocity, low water depth or outlet drops. The results of the barrier removal prioritization show that initial projects targeted for mitigation create much greater improvements in connectivity per unit cost than later projects. Benefit–cost curves from this type of analysis can be used to evaluate potential projects within and among watersheds and minimize overall expenditures for specified restoration targets.
Neeson, T., Ferris, M., Diebel, M., Doran, P., O’Hanley, J. and McIntyre, P. (2015). Enhancing ecosystem restoration efficiency through spatial and temporal coordination. Proceedings of the National Academy of Sciences USA 112:6236-6241.
In many large ecosystems, conservation projects are selected by a diverse set of actors operating independently at spatial scales
ranging from local to international. Although small-scale decision making can leverage local expert knowledge, it also may be an
inefficient means of achieving large-scale objectives if piecemeal efforts are poorly coordinated. Here, we assess the value of
coordinating efforts in both space and time to maximize the restoration of aquatic ecosystem connectivity. Habitat fragmentation
is a leading driver of declining biodiversity and ecosystem services in rivers worldwide, and we simultaneously evaluate optimal barrier removal strategies for 661 tributary rivers of the Laurentian Great Lakes, which are fragmented by at least 6,692 dams and 232,068 road crossings.We find that coordinating barrier removals across the entire basin is nine times more efficient at reconnecting fish to headwater breeding grounds than optimizing independently for each watershed. Similarly, a one-time pulse of restoration investment is up to 10 times more efficient than annual allocations totaling the same amount. Despite widespread emphasis on dams as key barriers in river networks, improving road culvert passability is also essential for efficiently restoring connectivity to the Great Lakes. Our results highlight the dramatic economic and ecological advantages of coordinating efforts in both space and time during restoration of large ecosystems.
King, S. and O’Hanley, J. (2014). Optimal fish passage barrier removal – Revisited. River Research and Applications [Online]. Available at: http://dx.doi.org/10.1002/rra.2859.
Infrastructure, such as dams, weirs and culverts, disrupt the longitudinal connectivity of rivers, causing adverse impacts on fish and other aquatic species. Improving fish passage at artificial barriers, accordingly, can be an especially effective and economical river restoration option. In this article, we propose a novel, mixed integer programing model for optimizing barrier mitigation decisions given a limited budget. Rather than simply treating barriers as being impassable or not, we consider the more general case in which barriers may be partially passable. Although this assumption normally introduces nonlinearity into the problem, we manage to formulate a linear model via the use of probability chains, a newly proposed technique from the operations research literature. Our model is noteworthy in that it can be readily implemented and solved using off-the-shelf optimization modelling software. Using a case study from the US State of Maine, we demonstrate that the model is highly efficient in comparison with existing solution methods and, moreover, highly scalable in that large problems with many thousands of barriers can still be solved optimally. Our analysis confirms that barrier mitigation can provide substantial ecological gains for migratory fish at low levels of investment.
O’Hanley, J., Scaparra, M. and García-Quiles, S. (2013). Probability chains: A general linearization technique for modeling reliability in facility location and related problems. European Journal of Operational Research [Online] 230:63-75. Available at: http://dx.doi.org/10.1016/j.ejor.2013.03.021.
In this paper, we propose an efficient technique for linearizing facility location problems with site-dependent failure probabilities, focusing on the unreliable p-median problem. Our approach is based on the use of a specialized flow network, which we refer to as a probability chain, to evaluate compound probability terms. The resulting linear model is compact in size. The method can be employed in a straightforward way to linearize similarly structured problems, such as the maximum expected covering problem. We further discuss how probability chains can be extended to problems with co-location and other, more general problem classes. Additional lower bounds as well as valid inequalities for use within a branch and cut algorithm are introduced to significantly speed up overall solution time. Computational results are presented for several test problems showing the efficiency of our linear model in comparison to existing
Warren, R., Lowe, J., Arnell, N., Hope, C., Berry, P., Brown, S., Gambhir, A., Gosling, S., Nicholls, R., O’Hanley, J., Osborn, T., Osborne, T., Price, J., Raper, S., Rose, G. and Vanderwal, J. (2013). The AVOID programme’s new simulations of the global benefits of stringent climate change mitigation. Climatic Change [Online] 120:55-70. Available at: http://dx.doi.org/10.1007/s10584-013-0814-4.
Quantitative simulations of the global-scale benefits of climate change mitigation are presented, using a harmonised, self-consistent approach based on a single set of climate change scenarios. The approach draws on a synthesis of output from both physically-based and economics-based models, and incorporates uncertainty analyses. Previous studies have projected global and regional climate change and its impacts over the 21st century but have generally focused on analysis of business-as-usual scenarios, with no explicit mitigation policy included. This study finds that both the economics-based and physically-based models indicate that early, stringent mitigation would avoid a large proportion of the impacts of climate change projected for the 2080s. However, it also shows that not all the impacts can now be avoided, so that adaptation would also therefore be needed to avoid some of the potential damage. Delay in mitigation substantially reduces the percentage of impacts that can be avoided, providing strong new quantitative evidence for the need for stringent and prompt global mitigation action on greenhouse gas emissions, combined with effective adaptation, if large, widespread climate change impacts are to be avoided. Energy technology models suggest that such stringent and prompt mitigation action is technologically feasible, although the estimated costs vary depending on the specific modelling approach and assumptions. © 2013 Springer Science+Business Media Dordrecht.
O’Hanley, J., Wright, J., Diebel, M., Fedora, M. and Soucy, C. (2013). Restoring stream habitat connectivity: A proposed method for prioritizing the removal of resident fish passage barriers. Journal of Environmental Management [Online] 125:19-27. Available at: http://dx.doi.org/10.1016/j.jenvman.2013.02.055.
Systematic methods for prioritizing the repair and removal of fish passage barriers, while growing of late, have hitherto focused almost exclusively on meeting the needs of migratory fish species (e.g., anadromous salmonids). An important but as of yet unaddressed issue is the development of new modeling
approaches which are applicable to resident fish species habitat restoration programs. In this paper, we develop a budget constrained optimization model for deciding which barriers to repair or remove in order to maximize habitat availability for stream resident fish. Habitat availability at the local stream
reach is determined based on the recently proposed C metric, which accounts for the amount, quality, distance and level of connectivity to different stream habitat types. We assess the computational performance of our model using geospatial barrier and stream data collected from the Pine-Popple Watershed, located in northeast Wisconsin (USA). The optimization model is found to be an efficient and practical decision support tool. Optimal solutions, which are useful in informing basin-wide restoration planning efforts, can be generated on average in only a few minutes.
Ioannidou, C. (2017). Optimising River Infrastructure Placement and Mitigation Decisions.
We address the problem of locating small hydropower dams in an environmentally friendly manner. We propose the use of a multi-objective optimization model to maximize total hydropower production, while limiting negative impacts on river connectivity. Critically, we consider the so called "backwater effects" that dams have on power generation at nearby upstream sites via changes in water surface profiles. We further account for the likelihood that migratory fish and other aquatic species can successfully pass hydropower dams and other artificial/natural barriers and how this is influenced by backwater effects. Although naturally represented in nonlinear form, we manage through a series of linearization steps to formulate a mixed integer linear programing model. We illustrate the utility of our proposed framework using a case study from England and Wales. Interestingly, we show that for England and Wales, a region heavily impacted by a large number of existing river barriers, installation of small hydropower dams fitted with even moderately effective fish passes can, in fact, create a win-win situation that results in increased hydropower and improved river connectivity.
We also propose a novel optimization framework to prioritize fish passage barrier mitigation decisions that incorporates both fish population and dispersal dynamics in order to maximize equilibrium population size. A case study involving a wild coho salmon (Oncorhynchus kisutch) population from the Tillamook basin, Oregon, USA is used to illustrate the benefits of our approach. We consider two extreme homing patterns, river and reach level homing, as well as straying. Under density dependent population growth, we find that the type of homing behavior has a significant effect on barrier mitigation decisions. In particular, with reach homing, our model results in virtually the same population sizes as a more traditional barrier prioritization procedure that seeks to maximize the accessible habitat. With river homing, however, there is no need to remove all barriers to maximize equilibrium population size. Indeed, a stochastic version of our model reveals that removing all barriers actually results in a marginal increase in quasi-extinction risk. We hypothesize that this is due to a population thinning effect of barriers, resulting in a surplus of recruits in areas of low spawner density. Our present study should prove useful to fish conservation managers by assessing the relative importance of incorporating spatiotemporal fish population dynamics in river connectivity restoration planning.
Finally, habitat fragmentation is a leading threat to global biodiversity. Restoring habitat connectivity, especially in freshwater systems, is considered essential in improving ecosystem function and health. Various studies have looked at cost effectively prioritizing river barrier mitigation decisions. In none of these, however, has the importance of accounting for the potential presence of unknown or "hidden" barriers been considered. In this study, we propose a novel optimization based approach that accounts for hidden barrier uncertainty in river connectivity restoration planning and apply it in a case study of the US state of Maine. We find that ignoring hidden barriers leads to a dramatic reduction in anticipated accessible habitat gains. Using a conventional prioritization approach, habitat gains are on average 60% lower than expected across a range of budgets when there are just 10% additional but unknown barriers. More importantly our results show that anticipating for hidden barriers can improve potential gains in accessible habitat in excess of 110% when the budget is low and the number of hidden barriers comparatively large. Finally, we find that solutions optimized for an intermediate number of unknown barriers perform well regardless of the actual number of hidden barriers. In other words, we can build-in robustness into the barrier removal planning framework. Dealing with the hidden elephant in the room could lead to a far more realistic approach of the habitat connectivity restoration issue.
Starita, S. (2016). Optimization Approaches To Protect Transportation Infrastructure Against Strategic and Random Disruptions.
Past and recent events have proved that critical infrastructure are vulnerable to natural catastrophes, unintentional accidents and terrorist attacks. Protecting these systems is critical to avoid loss of life and to guard against economical upheaval. A systematic approach to plan security investments is paramount to guarantee that limited protection resources are utilized in the most effcient manner. This thesis provides a detailed review of the optimization models that have been introduced in the past to identify vulnerabilities and protection plans for critical infrastructure. The main objective of this thesis is to study new and more realistic models to protect transportation infrastructure such as railway and road systems against man made and natural disruptions. Solution algorithms are devised to effciently solve the complex formulations proposed. Finally, several illustrative case studies are analysed to demonstrate how solving these models can be used to support effcient protection decisions.
Malik, S. (2015). Optimising Supermarket Promotions of Fast Moving Consumer Goods Using Disaggregated Sales Data: A Case Study of Tesco and Their Small and Medium Sized Suppliers.
The use of price promotions for fast moving consumer goods (FMCG’s) by supermarkets has increased substantially over the last decade, with significant implications for all stakeholders (suppliers, service providers & retailers) in terms of profitability and waste. The overall impact of price promotions depends on the complex interplay of demand and supply side factors, which has received limited attention in the academic literature. There is anecdotal evidence that in many cases, and particularly for products supplied by small and medium sized enterprises (SMEs), price promotions are implemented with limited understanding of these factors, resulting in missed opportunities for sales and the generation of avoidable promotional waste. This is particularly dangerous for SMEs who are often operating with tight margins and limited resources.
A better understanding of consumer demand, through the use of disaggregated sales data (by shopper segment and store type) can facilitate more accurate forecasting of promotional uplifts and more effective allocation of stock, to maximise promotional sales and minimise promotional waste. However, there is little evidence that disaggregated data is widely or routinely used by supermarkets or their suppliers, particularly for those products supplied by SMEs. Moreover, the bulk of the published research regarding the impact of price promotions is either focussed on modelling consumer response, using claimed behaviour or highly aggregated scanner data or replenishment processes (frameworks and models) that bear little resemblance to the way in which the majority of food SMEs operate.
This thesis explores the scope for improving the planning and execution of supermarket promotions, in the specific context of products supplied by SME, through the use of dis-aggregated sales data to forecast promotional sales and allocate promotional stock. An innovative case study methodology is used combining qualitative research to explore the promotional processes used by SMEs supplying the UK’s largest supermarket, Tesco, and simulation modelling, using supermarket loyalty card data and store level sales data, to estimate short term promotional impacts under different scenarios and derive optimize stock allocations using mixed integer linear programming (MILP).
The results suggest that promotions are often designed, planned and executed with little formalised analysis or use of dis-aggregated sales data and with limited consideration of the interplay between supply and demand. The simulation modelling and MILP demonstrate the benefits of using supermarket loyalty card data and store level sales data to forecast demand and allocate stocks, through higher promotional uplifts and reduced levels of promotional waste
Jeffries, T. (2015). Optimising Blood Donation Session Scheduling in South East England.
It is essential that all countries operate a form of blood banking service, where blood is collected at donation sessions, stored and then distributed to local healthcare providers. It is imperative that these services are efficiently managed to ensure a safe supply of blood and that costs and wastages are kept minimal. Previous works in the area of blood management have focussed primarily on the perishable inventory problem and on routing blood deliveries to hospitals; there has been relatively little work focusing on scheduling blood donation sessions.
The primary aim of this research is to provide a tool that allows the National Blood Service (the English and Welsh blood service) to schedule donation sessions so that collection targets are met in such a way that costs are minimised (the Blood Scheduling Problem). As secondary aims, the research identifies the key types of data that blood services should be collecting for this type of problem. Finally, various what-if scenarios are considered, specifically improv- ing donor attendance through paying donors and the proposed changes to the inter-donation times for male and female donors.
The Blood Scheduling Problem is formulated as a Mixed Integer Linear Programming (MILP) problem and solved using a variable bound heuristic. Data from the South East of England is used to create a collection schedule, with all further analysis also being carried out on this data set. It was possible to make improvements to the number of units under collected in the current schedule, moreover the number of venues and panels operated could be reduced. Further- more, it was found that paying donors to donate was uneconomical. Finally, changing the inter-donation times could lead to a reduction in the number of shortfalls, even when demand was increased by as much as 20%.
Though the model is specific to England and Wales, it can easily be adapted to other countries’ blood services. It is hoped that this model will provide blood services with a model to help them better schedule donation sessions and allow them to identify the data necessary to better understand their performance.
King, S. (2015). Economic Valuation and Optimisation of River Barrier Mitigation Actions.
Infrastructure, such as dams, weirs and culverts, disrupt the longitudinal connectivity of rivers, causing adverse impacts on fish and other species. This compromises the ability of river ecosystems to provide a range of services that contribute to human well-being. Improving fish passage at artificial barriers is an economic river restoration policy option that can improve the delivery of river ecosystem services provision. Whilst a number of methodologies exist to cost-effectively prioritize barriers for mitigation action, there is also now considerable interest in estimating the economic benefits of increased ecosystem service provision from investing in this activity. This is relevant in a number of policy contexts, including the Water Framework Directive in the EU. This thesis presents a novel bio-economic model that addresses the dual problem of prescribing cost optimal river barrier mitigation solutions whilst, simultaneously, estimating the social benefit of undertaking this activity. Minimal cost solutions are obtained for the problem of barrier mitigation decisions using a mixed integer linear program (MILP). The benefit from marginal improvements in river connectivity and fish species responses is then estimated using the Choice Experiment method. Incorporating these benefit estimates into the MILP generates the final bio-economic model. The specific advantage of this approach is it can readily inform cost benefit analysis of river barrier mitigation policy. The methods are demonstrated using the River Wey in South East England, containing over 650 artificial barriers, as a case study. For the case study, the benefits of investing in river barrier mitigation exceed costs at all budget levels, with the most socially efficient level of investment identified as approximately £30M.