Details of Award
NERC Reference : NE/K007165/1
[ENVIRONMENT] Measuring active layer depth to develop predictive models of mixed sediment beach response to wave energies.
Training Grant Award
- Lead Supervisor:
- Professor C Moses, University of Sussex, Sch of Global Studies
- Grant held at:
- University of Sussex, Sch of Global Studies
- Science Area:
- Marine
- Overall Classification:
- Marine
- ENRIs:
- Environmental Risks and Hazards
- Global Change
- Natural Resource Management
- Science Topics:
- None
- Abstract:
- Mixed sediment beaches (MSBs) with sediment sizes ranging over three orders of magnitude are an increasingly important defence against coastal flooding & erosion. Understanding MSB dynamics is relevant to the management of more than one third of the shoreline of England & Wales & almost all of the heavily populated SE coast of England. Some 70% of the latter's shoreline has a Hold the Line policy under which marine dredged aggregate (recharge), which is increasingly expensive, is added to maintain adequate beach volumes. Beaches lose sediment via longshore & offshore transport whose accurate quantification is critical to calculating recharge amounts needed for effective beach management. Industry does this using sediment transport modelling which depends on reliable input data & modelling assumptions. Tracer experiments to calculate longshore transport rates, require three measurements: distance travelled by the tracers' centre of mass or volume; thickness of the moving sediment layer (the active layer; AL); width over which transport occurs. On MSBs the latter two are often estimated & considered homogenous across & alongshore. Beach response to waves is controlled largely by permeability & that of MSB is highly variable. Recharging reduces it by introducing a higher proportion of fine sand. Limited field studies of MSB hydraulic conductivity focus on sediment movement mechanisms & profile changes, neglecting AL depth. This project combines fluvial & coastal sediment transport theories via innovative technologies to understand AL behaviour, about which little is currently known, to improve model input data & to inform MSB management policy and practice. The research focuses on a MSB type site at Hayling Island, Hampshire, with key sediment characteristics of MSBs yet sufficient variability in sediment mix & exposure to wave conditions to facilitate comparative studies. It is regularly recharged, giving an excellent opportunity to study AL response to this practice. The principal objective of this research is to confirm preliminary research that a predictive relationship between AL depth & wave height can be established for MSBs that will allow coastal managers to quantify the level of flood & erosion protection. The aim is to measure variations in AL depth & width on MSBs & characterise sediment permeability properties & wave energies that underpin its behaviour. By studying MSBs with different sediment compositions, it is hypothesised that: beach profile elevation changes are an uncertain guide to the maximum depth of the AL; sediment size distribution and packing patterns will strongly influence AL depth; there is a correlation between AL depth & wave height; there are identifiable lower & upper size limits at which sediment remains active on the beach. Experimental focus is on: measurement of AL depth, width & sediment movement, using innovative technologies provided by the project partner (PIT tag tracers) with established methods in coastal & fluvial science; characterisation of beach sediment properties across & along the beach, seasonally & following a recharge programme; measurement of sediment packing patterns, permeability & hydraulic conductivity. The AL response on MSBs with different sediment compositions will be used to identify the sediment characteristics that underpin its behaviour under a range of wave conditions. Focusing on Hayling Island frontage constrains variables to achieve a clear understanding of AL behaviour applicable to all MSBs. The key output is to develop a predictive model, that combines theoretical principles with empirical data, for MSB response to a range of wave conditions, including those anticipated under future climate change scenarios. MSBs are widespread along the Channels coasts & the Kent & East Anglian coastlines & the results of this innovative research will be of considerable value in informing management practice & policy in England and worldwide.
- NERC Reference:
- NE/K007165/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Open CASE
This training grant award has a total value of £73,368
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - Student Stipend | Total - RTSG |
|---|---|---|
| £13,978 | £49,194 | £10,198 |
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