3.1 Introduction
This chapter describes the components and architecture that make up an integrated system for use in coastal zone management. All future references to the ‘Integrated Wave Modelling System’, or IWMS, refer to the new system that has been developed in this research. The main aim was to run a coastal process model from within a GIS framework to investigate the benefits that can be derived from such a linkage. Ultimately the final system has gone further than this, with additional functionality that transforms the system from a tool that merely facilitates and extends the use of the coastal process model, into one which plays a full role in decision support for coastal zone managers.
The target users are defined as ‘anyone who may benefit from being able to generate information about changes in inshore wave climates’. This encompasses professionals with a wide skills range from dedicated wave modellers in coastal consultancy groups, to GIS consultants involved in environmental issues, through to those whose skills lie in coastal zone management who need inshore wave data to underpin ideas on how to approach local management issues.
This chapter describes the basic structure of the IWMS. This includes procedures to run the wave refraction model and new functionality for the display and analysis of model results. It also describes additional functionality for bathymetric analysis to describe the complexity of a study area. Specific developments for a typical dredging application which illustrate the flexibility of the system to be customised to meet the needs of a particular user group are discussed later in Chapter 7.
3.2 Integration Strategy
Two approaches can be taken when integrating two software entities into a single system - ‘fully integrated’ or ‘loosely coupled’. These options are described in Chapter 2 (section 2.7). A fully integrated system benefits from a single user interface and seamless operation, whereas the loosely coupled approach maintains the structure of its component parts relying on file transfer for the linkages. This results in a system, which although not as compact from a user perspective, is more flexible, and still maintains access to all component functionality.
The flexibility of the final system is an important consideration when working with coastal process models. Irrespective of the processes modelled by the algorithms, such models are typically complex and use a large number of both spatial and non-spatial inputs to generate results. The main issues under consideration when designing the system structure are detailed in Table 3.1
Issues Fully Integrated Approach Loosely - Coupled Approach
Algorithms Re-code into GIS macro
language.
Retain original coding
Processing Speed Algorithms would run much
slower in this format
Original processing speeds retained
User Interface Single interface which is
easy to use
Multiple interfaces which may increase system complexity
Adaptability Limited, as whole system
would need to be modified to incorporate new
functionality
New functions can be added as separate modules that uo not effect existing structures Linkage between software
entities
Close and fully automated Relies on file transfer and may require some user intervention.
The loosely coupled approach was adopted for this research for the following reasons: • When the two software entities to be integrated are fully developed in their own right,
there is little to be gained from trying to re-code wave model algorithms in GIS development languages purely to be able to run all the functions directly from a single user interface. Experience has shown that the resulting functionality is likely to be less flexible and run significantly slower. (Moore et al, 1997).
• By maintaining the integrity of the two software entities and relying on file transfer to achieve the integration, each one retains its full functionality and works at its original optimum processing speed.
• The flexibility of a loosely coupled structure ensures that users are not restricted to a single path through the system and that all modelling options remain available.
• The open structure allows easy modification to incorporate new functions for the requirements of different user groups.
The main drawback of this type of approach is that the modular structure makes use of more than one user interface. The GIS, the wave model, and other software packages that make up the system are all accessed through their own user interface. This could be perceived as problematic because the system as a whole becomes more complex to navigate than one in which there is only one interface to be mastered. This drawback was felt to be less important than the need to create a system that retained the original processing speed and functionality of the wave model whilst also being flexible enough to be easily modified to incorporate a range of functionality to suit a wide user group.
Wherever possible, fully automated procedures were implemented to achieve the integration, although some remain semi-automatic requiring user input of site specific information. Two-way links are implemented where it is advantageous to re-import data and results back into the GIS for visualisation and further analysis, and one-way links are used to give access to more sophisticated tools not available in the GIS.
3.3 System Components
The IWMS was intended to integrate coastal processing functionality into a GIS framework. The first step was to identify and procure the main system components. The key decision therefore was the choice of coastal process model and GIS that should be used.
3.3.1 Coastal Process Model
The principal factor affecting the choice of coastal process model was the need for a well-known and established model. A model fitting this criterion would have credibility in the wider user community. This steers the choice towards an older style of model that has been available for many years. The IWMS was to be a ‘proof of concept system’ and therefore it was not considered important to use the most advanced or newest model to produce the most sophisticated modelling system.
The vector wave ray type of wave refraction model is common and popular in industry and has been available to users for many years. For straightforward efficient wave refraction studies these models are still often used. The other available model types, such as finite difference réfraction-diffraction models and the 3"^^ generation Boussinesq models which also model energy inputs and losses within the system in general offer no significant advantages for the aims of this project. The main options considered for the choice of model are outlined in Figure 3.1.
Not Available
CHOSEN
CHOSEN