HR: 1340h
AN: GC33A-0960    [Abstracts]
TI: The Sensitivity of Coastal Cliffs to Changes in Sea Level
AU: * Rosser, N
EM: n.j.rosser@dur.ac.uk
AF: Institute of Hazard and Risk Research, Department of Geography, University of Durham, Science Labs., South Road, Durham, DH1 3LE, United Kingdom
AU: Lim, M
EM: michael.lim@newcastle.ac.uk
AF: School of Civil Engineering and Geosciences, Cassie Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom
AU: Petley, D
EM: d.n.petley@dur.ac.uk
AF: Institute of Hazard and Risk Research, Department of Geography, University of Durham, Science Labs., South Road, Durham, DH1 3LE, United Kingdom
AB: The impact of waves upon coastal cliffs is a significant control on erosion and subsequent cliff retreat. It is widely anticipated that climatically-driven sea-level rise will result in an increase in the rate of erosion, and thus the retreat, of coastal cliffs. Quantifying the changes in the rate of coastal erosion remains problematic, primarily due to the difficulty of collecting high-precision and high-frequency monitoring data on both cliff change and the variations in environmental conditions at the coast. In the UK, local authorities now have to produce a "Shoreline Management Plan" (SMP), indicating how the coastline will be managed for the future. This requires the estimation of rates of coastal retreat over the next century, making the impact of sea-level change a critical consideration. This study presents the results from a three year monitoring survey of a section of near-vertical coastal cliffs in north-east England. Data have been collected using a high-resolution terrestrial laser scanner to obtain cliff surfaces. Analysis of successive 3D cliff models is used to derive sequential change, from which the precise nature, geometry and rate of retreat can be measured. In parallel, data has been collected on the micro-seismic impact of waves onto the cliff to gain a direct measure of the delivery of energy at any given sea-level, rather than using a function of wave and tide gauge records. The coastline studied has a significant tidal range, in excess of 6 m, in addition to a large seasonal variability in mean tide heights, allowing a range of sea-level conditions to be assessed. For comparison weather, tide and wave monitoring has been undertaken. The results suggest a close link between the magnitude and frequency of wave impact and the loss of material from the cliff face. Marked changes in wave impact are apparent as the tide level fluctuates on an inter-monthly and inter-annual basis. Thresholds are identified which appear to reflect discrete changes in wave energy delivery as tidal level rises, possibly reflecting critical inundation depths and wave propagation up onto the cliff face. The cliff monitoring data show a similar sensitivity with a marked increase in absolute volumes of material loss, the location of these losses on the cliff face and the resulting effective rate of cliff face retreat. The results demonstrate the sensitivity of the cliffs and the short term variability in response. The study provides significant insights into both the likely future retreat of cliffs in response to climate change and perhaps more importantly the nature with which cliffs accommodate and respond to sea-level changes.
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1640 Remote sensing (1855)
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
DE: 4217 Coastal processes
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting