Conclusions

This chapter has outlined the design and described the functionality of the IWMS. The decisions involved in its design have been discussed to explain the implementation of the final procedures. Automated and semi-automated procedures ensure the close integration of the wave model and the GIS and offer great advantages over running the wave model independently.

This is seen in the following ways:

• In terms of the speed with which input data for the model can be generated.

• In the way the functionality of the wave model itself has been extended to generate more data.

• With functionality for visualisation of model results on the original bathymetry. • With automated procedures that reduce user errors.

Additional functionality developed within the GIS has been described in terms of how it develops the role of the GIS from simply supporting wave modelling, to providing pre and post processing tools for wave data, and bathymetry morphology analysis.

These additional functions help the significance of the model results to be understood in the context of their own study area and with reference to any specific changes under investigation. In this way the IWMS assists decision making and management strategy in the coastal zone.

C hapter 4 Analysis Data Sets

4.1 Introduction

This chapter introduces two data sets that have been used to test the working o f the IWMS described in Chapter 3. T hey represent tw o contrasting areas a llow in g the algorithms and analysis capability to be fully tested in a range o f conditions. Figure 4.1 sh ow s the location o f the two data sets, the N ash Bank in South W ales and the Yorkshire data around Scarborough.

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A s this figure show s, the tw o data sets are sited in areas o f very different character. The N ash Bank area is situated in the Bristol Channel in the south w est o f the country w hereas the Yorkshire data is in a far more open position on the east facing North Sea coast.

The N ash Bank data were loaned for use in this project by HR W allingford and the Yorkshire data lik ew ise from Scarborough Borough C ouncil. It should noted that all the tests on these data are d evised purely to a ssess the functionality o f the IW MS and do not represent o n goin g projects in either o f these areas.

4.2 Nash Bank

The Nash Bank dataset com es from a bottom sounding survey carried out by The Adm iralty in 1949. Its location is show n in Figure 4.2

Neath Swansea Port Talbot Swansea Bay Bridgend Porthcawl Nash Bank Bathymetry Data Not to scale Approximately 10km

Figure 4.2 Location o f N ash Bank bathymetry data

This area was originally surveyed to get information about a significant underwater offshore feature, known as the Nash Bank. This has a large impact on local coastal processes, and also provides a sediment store of sufficient size and quality to make it an economic dredging proposal for extraction of sand for the construction industry. (Details of a dredging proposal in this area are given in Chapter 8).

The original survey data were used to create a TIN for the whole study area. This was then overlain by a grid which is shown by the larger blue coloured surface shown in Figure 4.3. A graphic rectangle is used to nominate the working grid, which has to confoim to the input specifications described in chapter 3 (section 3.4.2.1). The resulting working grid is shown in the green/grey colours.

The working grid isolates an area approximately 11 x 6 km (66 km^). The density of the original survey points is fairly constant throughout with an approximate average spacing between survey points of 132m. The position of the Nash Bank feature shows up as a linear feature running approximately east-west across the bathymetry area

The complexity of the bathymetry makes it ideal for testing the functionality of the IWMS. It is expected that a complex area like this will display a large variation in inshore wave height which can be visualised and analysed. These data will therefore provide a good opportunity to assess the usefulness of the information that can be generated from the model results.

Port Talbot

Bridgend

Porthcawl

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Figure 4.3 D etails o f the N ash Bank bathymetry

4.3 Yorkshire

The Yorkshire data set is a com bination o f bottom sounding data collected in 2 0 0 0 on b eh alf o f Scarborough Borough C ouncil and additional data taken from Adm iralty Charts o f the area. T his data set is show n in Figure 4.4.

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S ca rb o ro u g h

Y ork sh ire B ath ym etry D ata

Not to scale B ridlin gton S cu nth orp e Approximately 10km Humber Estuary

Figure 4 .4 L ocation o f Yorkshire bathymetry data

In their entirety these data cover an area o f approxim ately 12,500 km , much larger than the N ash Bank data d iscussed previously. The contours and sparse spot depths that can be seen in Figure 4 .4 are the additions generated from the Admiralty Charts by HR W allingford, and the d en sely spaced data are from the sounding survey. In order for this area to be com parable to the N ash Bank, an area o f sim ilar size and shape w as used for the w ave m od elling. This is show n in Figure 4.5 outlined by the graphic rectangle.

Scarborough

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Figure 4.5 Section o f the Yorkshire bathymetry used in this research

The inshore area of densely spaced survey points consists of bottom soundings taken in rows approximately 50 m apart with depths measured every 20 - 40m, giving an average spacing of 27m. This gives great detail in the inshore area directly off the coast of Scarborough. The data taken from the Admiralty Charts has been captured for each 5m contour near the coastline. This includes the 0, 5, 10, 15, and 20m contours which are separated by a few hundred metres. This then changes to include contours every 10m for the deeper 30,40, 50, and 60m contours which are separated by up to 2.5km. There is one land contour at -4m. Taking all the data together the average data spacing is 183m.

The simplicity of this area makes it an ideal test companion to the Nash Bank data. This form of bathymetry would be expected to generate much less variation in inshore wave height. It will be used to investigate how the IWMS functionality operates in a simple area with more predictable wave climates.

The analysis grid generated for the IWMS can be seen in Figure 4.6. Again the smaller working grid with the green/grey colours is shown superimposed on the larger blue coloured grid generated for the whole data set. By making the grid this size, the working area contains the densely surveyed portion of the seabed, and the grid remains directly comparable to the Nash Bank data.

Scarborough

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4.4 Summary

Choosing these two areas to test the IWMS should illustrate its ability to model areas of very different character successfully. The inshore wave height variation is expected to be very different. The Nash Bank data will demonstrate what information can be generated about the inshore wave climates in very complex areas, whereas the Yorkshire data will show what can be achieved when changes are more subtle.