volumetric computations. On land, the lines can usually be adjusted to 

 accomodate unusual features. However, a major limitation of hydrographic 

 surveys is that the operators cannot see significant morphological changes 

 beforehand. For example, sand waves parallel to the survey track line or rock 

 pinnacles may not be recorded, yet these features may represent a significant 

 volume of material. In effect, these features are smoothed out of the data set. 

 Saville and Caldwell (1953) estimated that spacing errors were much more 

 important than measurement errors. They provided some figures and formu- 

 las for estimating these errors, although their work may need to be updated. 



Coastal Data Interpretation with Numerical Models 



Introduction 



The use of numerical models in assessing changes in coastal geomorph- 

 ology is rapidly increasing in sophistication. Models are designed to numeri- 

 cally simulate hydrodynamic processes or simulate sediment response on 

 beaches, offshore, and in inlets. Specific types include models of wave 

 refraction and longshore transport, beach profile response, coastal flooding, 

 and shoreline change and storm-induced beach erosion (Birkemeier et al. 

 1987; Komar 1983; Kraus 1990). The judicious use of prototype data and 

 models can greatly assist the understanding of coastal processes and landforms 

 at a study site. Because models should be tested and calibrated, field data 

 collection or mathematical simulations of waves, tides, and winds at a project 

 site are usually required. 



The advantage of tools like numerical models is that they can simulate 

 phenomena only rarely observed, can generate complex and long-duration 

 changes, and can incorporate judgements and measurements from many 

 sources. The use of numerical models is a highly specialized skill, requiring 

 training, an understanding of the underlying mathematics, and empirical ("real 

 world") experience of coastal processes. This section summarizes types of 

 models and introduces some of their strengths and limitations. 



Types of models 1 



Coastal experience / empirical models. This represents the process by 

 which an understanding or intuitive feeling of coastal processes and 

 geomorphology is adapted and extrapolated from a researcher's experience to 

 a specific project. Prediction through coastal experience without the support 

 of objective quantitative tools has many limitations, including severe subjectiv- 

 ity and a lack of criteria to use for optimizing projects. Complete reliance on 

 coastal experience places the full responsibility for project decisions on the 



120 



Material in this section has been summarized from Kraus (1989). 



Chapter 5 Analysis and Interpretation of Coastal Data 



