DAEM Model Inventory

As part of the BGS strategy (BGS, 2009) the need to develop an Environmental Modelling Platform (EMP) has been identified. The Data and Applications for Environmental Modelling (DAEM) project has sought to scope out the requirements for an EMP. The DAEM project has four deliverables: a scoping study, an outline project plan for the next five years, a model inventory of model codes currently used within NERC, and community building. The scoping study together with the plan for the next five years has been published as a separate document (Giles et al., 2010). This report, an inventory of current Earth science models (and code) used by NERC centres, was created to form part of the appendices for the scoping study (Giles et al., 2010), but has since been commissioned as a separate report. The description for each model has come from the NERC institute indicated in the report. Where a description has not been given, a web search was used to compile the model information. Earth system modelling is undertaken at the majority of NERC centres, however where no information was given, found, or if no models are used, that centre has not been included in this report. Each entry contains a brief description of the model background, capabilities, and references to further information. The contact and use given for each model is specific to that NERC centre or department and therefore there are occasions where the same model is referenced more than once. The NERC contact cited has some degree of experience in using the model and in most cases should be able to answer related questions or direct queries to a suitable person if the required information can not be found via the link provided. The code language and runtime platform are included to aid with determine the ease of model linkages. As many relevant staff in the NERC centre/surveys were approached and consulted as possible. Whilst every effort has been undertaken to ensure the accuracy and completeness of this report, it is not necessarily comprehensive and the DAEM project team apologises in advance for any omissions

CLiDE version 1.0 user guide

The Dynamic Environmental Sensitivity to Change (DESC) project coupled cellular automaton (CA) modelling from various backgrounds and produced the CAESAR-Lisflood-DESC (CLiDE) modelling platform: a geomorphological simulator that allows a variety of Earth system interactions to be explored. A derived version of the well established Cellular Automaton Evolutionary Slope and River (CAESAR) model (Coulthard and Van De Wiel, 2006), CAESAR-Lisflood, which incorporates the Lisflood hydrodymanic model (Coulthard et al., 2013) to simulate channel and overbank flow, is used as the platform kernel. The two dimensional modular design allows great versatility in the range of simulated spatio-temporal scales to which it can be applied. CAESAR has been used to investigate a variety of sediment transport, erosional and depositional processes under differing climatic and land use pressures in river reaches and catchments (Hancock et at., 2011). The recent addition of Lisflood to the code improves the representation of surface water flow within the model by incorporating momentum. However, as with many landscape evolution models (LEMs), CAESAR over-simplifies the representation of some of the hydrological processes and interactions that drive sediment transport. Specifically, it does not simulate groundwater flow and its discharge to rivers. To address these limitations, the non-Lisflood controlled surface hydrological processes within the CLiDE platform are replaced with a bespoke distributed hydrological model that includes a groundwater model. This hydrological model partitions rainfall between surface run-off and recharge to groundwater using a soil water balance model, which is applied at each grid cell. To simulate groundwater flow to river channels we incorporate a single layer finite difference model into the code. This solves the governing partial differential groundwater flow equation using a forward time-stepping, or explicit, solution method (Wang and Anderson, 1982), which can be considered as a cellular automaton (CA) model (Ravazzani et al., 2011). The groundwater model is coupled to the surface model through the exchange of recharge and baseflow. In addition to the hydrological modifications, a debris flow component has been added to the platform. The triggering aspect of this component is linked to simulated groundwater levels

Coastal vulnerability of a pinned, soft-cliff coastline. Part II, assessing the influence of sea walls on future morphology

Coastal defences have long been employed to halt or slow coastal erosion, and their impact on local sediment flux and ecology has been studied in detail through field research and numerical simulation. The nonlocal impact of a modified sediment flux regime on mesoscale erosion and accretion has received less attention. Morphological changes at this scale due to defending structures can be difficult to quantify or identify with field data. Engineering-scale numerical models, often applied to assess the design of modern defences on local coastal erosion, tend not to cover large stretches of coast and are rarely applied to assess the impact of older structures. We extend previous work to explore the influences of sea walls on the evolution and morphological sensitivity of a pinned, soft-cliff, sandy coastline under a changing wave climate. The Holderness coast of East Yorkshire, UK, is used as a case study to explore model scenarios where the coast is both defended with major sea walls and allowed to evolve naturally were there are no sea defences. Using a mesoscale numerical coastal evolution model, observed wave-climate data are perturbed linearly to assess the sensitivity of the coastal morphology to changing wave climate for both the defended and undefended scenarios. Comparative analysis of the simulated output suggests that sea walls in the south of the region have a greater impact on sediment flux due to increased sediment availability along this part of the coast. Multiple defence structures, including those separated by several kilometres, were found to interact with each other, producing complex changes in coastal morphology under a changing wave climate. Although spatially and temporally heterogeneous, sea walls generally slowed coastal recession and accumulated sediment on their up-drift side

Coastal vulnerability of a pinned, soft-cliff coastline. Part I, assessing the natural sensitivity to wave climate

The impact of future sea-level rise on coastal erosion as a result of a changing climate has been studied in detail over the past decade. The potential impact of a changing wave climate on erosion rates, however, is not typically considered. We explore the effect of changing wave climates on a pinned, soft-cliff, sandy coastline, using as an example the Holderness coast of East Yorkshire, UK. The initial phase of the study concentrates on calibrating a numerical model to recently measured erosion rates for the Holderness coast using an ensemble of geomorphological and shoreface parameters under an observed offshore wave climate. In the main phase of the study, wave climate data are perturbed gradually to assess their impact on coastal morphology. Forward-modelled simulations constrain the nature of the morphological response of the coast to changes in wave climate over the next century. Results indicate that changes to erosion rates over the next century will be spatially and temporally heterogeneous, with a variability of up to ±25% in the erosion rate relative to projections under constant wave climate. The heterogeneity results from the current coastal morphology and the sediment transport dynamics consequent on differing wave climate regimes

Assessing the influence of sea walls on the coastal vulnerability of a pinned, soft-cliff, sandy coastline

Coastal defences have long been employed to halt or slow coastal erosion. Their impact on local sediment flux and ecology has been studied in detail through field studies and numerical simulations. The non-local impact of a modified sediment flux regime on mesoscale erosion and accretion has received less attention. Morphological changes at this scale due to defended structures can be difficult to quantify or identify with field data. Engineering scale numerical models, often applied to assess the design of modern defences on local coastal erosion, tend not to cover large stretches of coast and are rarely applied to assess the impact of older structures. We extend previous work to explore the influences of sea walls on the evolution and morphological sensitivity of a pinned, soft-cliff, sandy coastline under a changing wave climate. The Holderness coast of East Yorkshire, UK, is used as a case study, represented both as a defended example with major sea walls included and a natural example where no sea defences exist. Using a mesoscale numerical coastal evolution model, stochastic wave climate data are perturbed gradually to assess the sensitivity of the coastal morphology to changing wave climate for both the defended and natural scenarios. Comparative analysis of the simulated output suggests that sea walls in the south of the region have a greater impact on sediment flux due to the increased sediment availability along this part of the coast. Multiple defended structures, including those separated by several kilometres, were found to interact with each other, producing a complex imprint on coastal morphology under a changing wave climate. Although spatially and temporally heterogeneous, sea walls generally slowed coastal recession and accumulated sediment on their up-drift side

Exploring the sensitivities of crenulate-bay shorelines to wave climates using a new vector-based one-line model

We use a new exploratory model that simulates the evolution of sandy coastlines over decadal to centennial timescales to examine the behavior of crenulate-shaped bays forced by differing directional wave climates. The model represents the coastline as a vector in a Cartesian reference frame, and the shoreface evolves relative to its local orientation, allowing simulation of coasts with high planform-curvature. Shoreline change is driven by gradients in alongshore transport following newly developed algorithms that facilitate dealing with high planform-curvature coastlines. We simulated the evolution of bays from a straight coast between two fixed headlands with no external sediment inputs to an equilibrium condition (zero net alongshore sediment flux) under an ensemble of directional wave climate conditions. We find that planform bay relief increases with obliquity of the mean wave direction, and decreases with the spread of wave directions. Varying bay size over 2 orders of magnitude (0.1–16 km), the model predicts bay shape to be independent of bay size. The time taken for modeled bays to attain equilibrium was found to scale with the square of the distance between headlands, so that, all else being equal, small bays are likely to respond to and recover from perturbations more rapidly (over just a few years) compared to large bays (hundreds of years). Empirical expressions predicting bay shape may be misleading if used to predict their behavior over planning timescales

Aeolian sediment reconstructions from the Scottish Outer Hebrides: Late Holocene storminess and the role of the North Atlantic Oscillation

Northern Europe can be strongly influenced by winter storms driven by the North Atlantic Oscillation (NAO), with a positive NAO index associated with greater storminess in northern Europe. However, palaeoclimate reconstructions have suggested that the NAO-storminess relationship observed during the instrumental period is not consistent with the relationship over the last millennium, especially during the Little Ice Age (LIA), when it has been suggested that enhanced storminess occurred during a phase of persistent negative NAO. To assess this relationship over a longer time period, a storminess reconstruction from an NAO-sensitive area (the Outer Hebrides) is compared with Late Holocene NAO reconstructions. The patterns of storminess are inferred from aeolian sand deposits within two ombrotrophic peat bogs, with multiple cores and two locations used to distinguish the storminess signal from intra-site variability and local factors. The results suggest storminess increased after 1000 cal yrs BP, with higher storminess during the Medieval Climate Anomaly (MCA) than the LIA, supporting the hypothesis that the NAO-storminess relationship was consistent with the instrumental period. However the shift from a predominantly negative to positive NAO at c.2000 cal yrs BP preceded the increased storminess by 1000 years. We suggest that the long-term trends in storminess were caused by insolation changes, while oceanic forcing may have influenced millennial variability

Complex coastlines responding to climate change: do shoreline shapes reflect present forcing or “remember” the distant past?

A range of planform morphologies emerge along sandy coastlines as a function of offshore wave climate. It has been implicitly assumed that the morphological response time is rapid compared to the timescales of wave climate change, meaning that coastal morphologies simply reflect the extant wave climate. This assumption has been explored by focussing on the response of two distinctive morphological coastlines – flying spits and cuspate capes – to changing wave climates, using a coastline evolution model. Results indicate that antecedent conditions are important in determining the evolution of morphologies, and that sandy coastlines can demonstrate hysteresis behaviour. In particular, antecedent morphology is particularly important in the evolution of flying spits, with characteristic timescales of morphological adjustment on the order of centuries for large spits. Characteristic timescales vary with the square of aspect ratios of capes and spits; for spits, these timescales are an order of magnitude longer than for capes (centuries vs. decades). When wave climates change more slowly than the relevant characteristic timescales, coastlines are able to adjust in a quasi-equilibrium manner. Our results have important implications for the management of sandy coastlines where decisions may be implicitly and incorrectly based on the assumption that present-day coastlines are in equilibrium with current conditions

Lessons learned from improved land management schemes and their effect on gully erosion control – a review

The ill-management of headwaters has frequently shown to severely impact the fluvial environment, with channel incision and gully erosion hazards affecting many areas around the world, especially in drylands. To counter this, many regions have adopted improved land management schemes aiming at restoring the physical, biological and hydrological integrity of the landscape. Therefore, much attention has been given to the rehabilitation and renaturalization of headwater streams and gullies. Despite recent successes in land rehabilitation for many areas worldwide, optimizing the management of (agricultural) landscapes remains challenging, especially considering global trends in land use and climate change. In this paper, an analysis is presented on indirect (catchment-wide) and direct (operating at the channel) gully rehabilitation measures and their success, by reviewing literature from dryland environments across the world. Understanding the success of gully rehabilitation measures was done by adding the life-cycle of a gully to the analysis, indicating that the success of gully rehabilitation is linked to the hydrogeomorphic development phase of gullies. From cut to fill cycle, gullies typically develop through a number of hydrogeomorphic phases, in which different geomorphic responses become dominant (from headcut retreat and downcutting, to widening and eventually, infilling). This has important implications for the type of interventions required to control gully development and the costs involved. Moreover, this analysis teaches us when (appropriate timing) and where (appropriate area) to start gully rehabilitation schemes, when cost-effective and sustainable solutions are sought

The effectiveness of beach mega-nourishment, assessed over three management epochs

Resilient coastal protection requires adaptive management strategies that build with nature to maintain long-term sustainability. With increasing pressures on shorelines from urbanisation, industrial growth, sea-level rise and changing storm climates soft approaches to coastal management are implemented to support natural habitats and maintain healthy coastal ecosystems. The impact of a beach mega-nourishment along a frontage of interactive natural and engineered systems that incorporate soft and hard defences is explored. A coastal evolution model is applied to simulate the impact of different hypothetical mega-nourishment interventions to assess their impacts’ over 3 shoreline management planning epochs: present-day (0–20 years), medium-term (20–50 years) and long-term (50–100 years). The impacts of the smaller interventions when appropriately positioned are found to be as effective as larger schemes, thus making them more cost-effective for present-day management. Over time the benefit from larger interventions becomes more noticeable, with multi-location schemes requiring a smaller initial nourishment to achieve at least the same benefit as that of a single-location scheme. While the longer-term impact of larger schemes reduces erosion across a frontage the short-term impact down drift of the scheme can lead to an increase in erosion as the natural sediment drift becomes interrupted. This research presents a transferable modelling tool to assess the impact of nourishment schemes for a variety of sedimentary shorelines and highlights both the positive and negative impact of beach mega-nourishment