4 Investigation of 



Environmental Factors 



Geomorphic variability is chiefly caused by the work of dynamic envi- 

 ronmental factors that vary over time and space. The most important of these 

 factors are waves, tides, and currents which continually affect the shore and 

 upper shoreface. During periodic storms, these factors affect a much wider 

 zone, producing large-scale changes in geomorphic features. Because of this, 

 data on geomorphic variations in the coastal zone are much more valuable 

 when accompanied by wave and current observations for the same time period 

 so that process-response relationships can be examined. This portion of the 

 report concerns the equipment and techniques used to gather wave and current 

 data. 



Wave Data 



Methods of obtaining wave data include gages, hindcasting from weather 

 maps, shipboard observations, and littoral environment observations. Gages 

 are the most accurate of these methods, but their relative cost often restricts 

 their use to short-term deployments for the purpose of validating data col- 

 lected by observation or hindcasting methods. Multiple gages across the shore 

 zone in both shallow and deep water can be used to determine the accuracy of 

 wave transformation calculations for a specific locale. 



Wave gages can be separated into two general groups: directional and 

 non-directional. In general, directional gages are more expensive to build, 

 deploy, and maintain than non-directional gages. Because wave direction is 

 an important parameter in applications such as sediment transport analysis and 

 calculation of wave transformation, the additional expense is often necessary. 

 Wave gages in both categories can be installed in buoys, placed directly on the 

 sea or lake bottom, or mounted on existing structures, such as piers, 

 navigation aids, and offshore platforms. 



Buoy-mounted non-directional gages are accurate and relatively easy to 

 deploy and maintain. Data are usually transmitted by radio from the buoy to 



Chapter 4 Investigation of Environmental Factors 



65 



