2 Categorisation 2.1
Introduction
The objective of the categorisation process is to group inland waterways according to common function and character, with the understanding that waterways in the same category would respond similarly to policy scenarios. The intention is to produce a manageable number of categories that are meaningful, intuitively sensible and that would also offer variation in their response to research scenarios across categories. The use of GIS to facilitate categorisation is intended to allow the systematic allocation of categories to waterways using recognised national datasets of information concerning the wider environment. To enable this, the first step was to establish a baseline of waterways for which the categorisation would be undertaken. Data were collated for British Waterways, Defra and other freely available sources to populate the GIS database.
2.2
Categorisation
The difference between a canal and a river was recognised as a key waterway distinction as it influences likely usage and acts as a parameter to represent physical form. Similarly, the difference between urban and rural nature of the waterway environment was identified for incorporation as this influences both the types of user and features of the waterway which require maintenance. The urban /rural split is also considered to represent current and potential visitor levels to some extent as these are expected to be higher in urban areas than rural areas. Once the range of influencing parameters were identified and considered, it quickly became apparent that the number of sub-categories would have to be limited to keep the categorisation manageable. Therefore, only canal / river and urban / rural were selected as the main parameters. Applying just these parameters, results in four potential combinations and therefore four waterways categories. A final variable was sought to represent usage of the waterway. The inclusion of a distinction between usage volumes or rates was considered to be imperative to realising the variation in waterway response to scenario benefits. Boat density data were selected to represent this. Inland waterways data were provided by British Waterways in two GIS shapefiles, namely BW_waterways.SHP and AINA_waterways.SHP, which were used as the baseline for categorisation. The data are made up of short polyline reaches (mainly 1km in length) which are assigned a common waterway name; therefore multiple reaches comprise a single waterway. Presented in this format, the data are summarised by the following statistics for England and Wales: -
BW_waterways.SHP: 3213 reaches, 3081km total length AINA_waterways.SHP: 3320 reaches, 1921km total length7
There was some consideration of whether the study should dissolve waterway reaches into longer polylines on the basis of common name; however this approach 7
The Association of Inland Navigation Authorities (AINA) dataset relates to waterways managed by other AINA members excluding British Waterways. 6