Details of Grant 

EPSRC Reference:	EP/N011252/1
Title:	Theoretical modelling of shoreline protection by coastal vegetation
Principal Investigator:	Chan, Dr I
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Civil Engineering
Organisation:	University of Dundee
Scheme:	First Grant - Revised 2009
Starts:	01 December 2015	Ends:	30 November 2017	Value (£):	97,925
EPSRC Research Topic Classifications:	Coastal & Waterway Engineering
EPSRC Industrial Sector Classifications:	Environment
Related Grants:
Panel History:	Panel Date Panel Name Outcome 01 Oct 2015 Engineering Prioritisation Panel Meeting 1 October 2015 Announced
Summary on Grant Application Form
Traditionally, we defend our coastlines from storm surges and other powerful ocean waves by building hard structures, such as breakwaters and seawalls. Recently though, seacoast towns have begun to use environmentally sustainable engineering strategies such as augmenting the natural protective function of coastal vegetation. Soft as this may seem, it can be very effective. In the 2004 Indian Ocean Tsunami that affected India, Sri Lanka, and Thailand, mangroves, coconut trees, and cashew nut trees reduced the worst impact of the waves. And on the east coast of England, where the waves are more moderate, field experiments conducted by coastal geomorphologists show that significant damping of wave amplitude takes place in areas of salt marshes. Theoretical models that aim to explain this use of coastal vegetation are often based on the heuristic drag force formula for the interaction of waves and vegetation. Wave dissipation by a vegetated bed is modelled by an ad hoc term added to the assumed equations of motion with an empirical drag coefficient determined using field data or laboratory measurements. The methodology is attractive because it is simple. Unfortunately, it predicts only a bulk wave attenuation rate. It does not account for variations in the space between plants. In many coastal environments, the typical plant spacing (micro scale) can be orders of magnitude smaller than the wavelength of interest (macro scale). Since the wave energy dissipation results mainly from the turbulence generated by interstitial dynamics, it would be better to develop a theory for macro wave motion from the micro physics upwards. That is what this project will do. It will make use of the sharp contrast between the wave length and the plant spacing that exists in many coastal environments and apply the two-scale method of homogenisation to derive the effective macro equations for wave motion with the constitutive coefficients representing the effects of vegetation. The coefficients are computed from the solution of the micro flow problem for a small region surrounding only a few plants. A computational model based on the new mathematical model will be developed and will reflect the key feature of the proposed methodology: the macro scale wave problem and the mechanics of the micro scale vegetation will be solved separately. The new theory will be more computationally expedient than existing numerical models that resolve small-scale dynamics. That will make it more affordable to use for large-scale engineering problems at the same time as providing a more robust theoretical basis than the older drag force approach. The outcome of this work will be a scientific understanding of how exactly how coastline plants impede the approach of wave surges. This new knowledge will provide the technical know-how for effectively planting trees and other vegetation as sustainable engineering solutions for coastal protection.
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Organisation Website:	http://www.dundee.ac.uk