Kenneth Pye
Associates
Ltd.
Scientific Research,
Consultancy and Investigations
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Beach Topographic Variability in Relation to Significant Biological Change
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Webb, H., Pye, K., Huckle, J. and Blott, S.J. (2010) Beach Topographic Variability in Relation to Significant Biological Change. Report to Countryside Council for Wales by APEM Ltd. and Kenneth Pye Associates Ltd., CCW Contract Science Report No 906, Countryside Council for Wales, Bangor, xiii + 160 pp. Executive Summary The Welsh Assembly
Government (WAG) is funding the development of an all Wales Monitoring Centre
that will collate and manage regional shoreline data. This national scale
background monitoring will complement strategic investigations at a regional
level. It is vital that full use is made of the information that the Monitoring
Centre generates to ensure the funding delivers best value.
This project is designed to assist Countryside Council for Wales (CCW) to
specify its data requirements and thus maximise the use of the Monitoring Centre
from the outset. For
CCW, a major driver for physical and biological monitoring arises from
international and national obligations with respect to nature conservation. The
data held by the Monitoring Centre will underpin the identification and
monitoring of regional changes and will inform protected site management in
terms of reporting and understanding changes occurring at each sites. CCW
spends a great deal of effort characterising and mapping inter-tidal habitats in
Wales and undertakes an extensive program of biological monitoring. However,
monitoring of coastal physical processes and morphological change undertaken by
CCW is very limited; therefore, there is a valuable opportunity to maximise the
use of physical data gathered and reported on by the Monitoring Centre. Key to
achieving this is the development of an integrated programme which combines
physical and biological monitoring. CCW would also like to identify
environmental thresholds relevant to each biotope and designated area of
conservation interest. Such thresholds would inform site management and trigger
appropriate conservation activities. An understanding of the extent and
timescales of topographic variability of different types of coastal profile is
also required for assisting in prescribing operational management plans to
minimise the potential impacts of pollution events such as the 1996 Sea Empress
disaster in Milford Haven. A key aim of this project was to provide a review of the nature of coastal monitoring that is currently being undertaken elsewhere, so that appropriate recommendations as to CCW’s data requirements can be made to the new Monitoring Centre. These recommendations concern the measurement and reporting of environmental processes and features which are of biological significance. Many
environmental factors exert an influence on coastal biological communities,
principally water quality, exposure to wave action, tidal range, and tidal
currents. A review of the definitions and terminology used when describing these
environmental factors is presented to set the
context for the rest of the report and to assist in identifying
environmental trigger thresholds for key ecological features. A thorough review of relevant published and unpublished information relating to beach volatility and biological communities was undertaken. A number of key ecological features were selected as case studies, namely: Sabellaria reefs, Eelgrass (Zostera sp.) beds, beaches supporting the amphipod Pectenogammarus planicrurus, low shore and sub-littoral bivalve-rich communities, and muddy gravels. Key biological sensitivities in relation to changes in physical characteristics of beaches were identified and where possible, thresholds of topographic change defined. Such thresholds would indicate where biological changes are likely to occur and could be used as triggers for reporting/notification of change to CCW. This review considers both beach topography and associated changes in the hydrodynamic regime. The
physical requirements of the case study species and communities could be defined
in a broad qualitative sense. However,
the ability to ascribe quantitative levels of change in physical environmental
variables as causes of biological change requires more work before a robust
assessment of significant impacts on species and habitats can be made. A key
factor in gaining this understanding is developing an improved knowledge base
regarding the levels of ‘natural’ change occurring in coastal environments. The
importance of monitoring changes in beach and nearshore morphology has been
recognised for many years. An
overview of the main methodologies available for the monitoring of beach/nearshore
topographic change and the driving environmental processes has been provided,
including those currently used in Strategic Regional Coastal Monitoring
Programmes (SRCMPs) in England. For monitoring coastal change these include
visual observation and photography, land-based surveying, hydrographic surveys,
aerial photography and photogrammetry, CASI, satellite imagery and LiDAR. The
methods and importance of monitoring the physical forcing factors such as tidal
levels and currents, wind speed, wind direction and wave action, including
examples of the types of data which can be gathered, is also given along with
methods used to monitor sediment characteristics.
The issues surrounding beach volatility and biological communities were considered within the context of a number of selected case study areas (Traeth Crugan, Morfa Dyffryn, the Dyfi Estuary, and Burry Inlet). These case studies were used to identify some of the key data requirements for each of the sites that the Monitoring Centre could deliver and thereby demonstrate the practical applications of the results of this study. Existing SRCMPs throughout the UK have developed a relatively comprehensive set of procedures for data capture and reporting and a great deal of the information being gathered is relevant to biological conservation interests. To date, these results have been poorly integrated with ecological and wider environmental monitoring. An overview is provided of the methods for the monitoring of beach topographic variability carried out by these SRCMPs. The frequency and intensity of the monitoring employed is generally considered adequate for the purposes of monitoring medium to longer term changes (at annual to decadal timescales). Such methods are therefore highly relevant to the assessment of medium term threats to habitats of national and international conservation importance. The current monitoring programmes may be less adequate for the purposes of biological monitoring of species and communities where their survival may be as much dependent on the occurrence of extreme events as on long-term changes. Short-lived episodes of very low or very high beach levels may not, for example, be detected by annual or bi-annual monitoring; to obtain a true picture of beach topographic variability high frequency monitoring may be required, ideally after, or even during, individual tides. An understanding of short-term changes in beach levels need to be accompanied by a knowledge of the associated variations in surface sediment mobility and particle size characteristics, which exert a significant influence on many species. The data to be
held by the Monitoring Centre offers great potential to assist in defining
thresholds of topographic change above which biological changes are likely to
occur and which could be used as triggers for reporting/notification of change
to CCW. For some habitats and
species, for which there is a better understanding of the biological
implications of physical changes in beach topography, such thresholds would be
relatively easy to define. For most
ecological features however, more work is required before these quantitative
thresholds could be set. Individual
critical levels established by niche modelling or further field investigations
would be required in order to specify reporting requirements. The strategic
regional monitoring should be supplemented by more detailed local area studies
to achieve a better understanding of critical thresholds of topographic change,
sediment character and water quality which are relevant to particular species
and communities of national and international conservation interest. |
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