or long-term unidirectional trends that may be climatic or related to changes in 

 relative sea level and/or sediment supply. The planning and design of coastal 

 engineering projects and the long-term management of coastal areas require a 

 basic knowledge of the likely geomorphic variations that can be expected to 

 occur during the lifetime of the project. Thus, before plaiming and designing, 

 some study of the environmental and geomorphic features of the coastline to 

 be engineered, and its relation to adjacent coastlines, should be given detailed 

 attention. 



Many types of processes occur in the coastal zone. Inland of the coastline, 

 terrestrial processes are dominant, except during severe storm surges and 

 where the coastline is on a barrier backed by marginal marine features such as 

 lagoons, sounds, bays, and marshland. The shore and shoreface are the main 

 focuses of coastal marine processes: waves, currents, tides, and storm surges. 

 Seaward of the shoreface, inner Continental Shelf features such as linear and 

 arcuate shoals may change because of interaction with large waves and storm- 

 generated shelf currents. Other important causes of change in coastal zone 

 features are changes in relative sea level, increase or decrease of sediment 

 supply, and construction of engineering projects. Processes acting on 

 consolidated rock are usually much slower to bring about significant 

 morphological change, and some features may remain relatively unchanged for 

 centuries. Also, some changes such as relative sea level may take place so 

 slowly that they are difficult to detect and measure. 



Data collection on temporal changes in coastal features and environmental 

 factors is often difficult and expensive. Ideally, time-series data should cover 

 periods of several years, but this is rarely possible because of required lead 

 time and funding constraints. In some cases, there are historical resources in 

 the form of earlier hydrographic surveys, aerial photography, and prior 

 studies that can provide information about past temporal changes, but many 

 are deficient in detail, quality, time span, or frequency of observations and 

 measurements. 



It is important to obtain data on the processes, such as waves and currents, 

 that affect coastal features and, insofar as possible, gain an understanding of 

 the connection between processes and variable geomorphic features. Many 

 instruments are now available for acquiring time-series data on waves, 

 currents, winds, and other dynamic factors of the environment. Although 

 capable of obtaining high quality data, these techniques of data collection can 

 be expensive if used alone. With good historical sources such as weather 

 charts, much can be learnetl concerning factors such as waves and storm 

 surges by hindcasting, and instruments may be more economically used in a 

 limited role to verify data. The difficulty in measuring many environmental 

 factors is primarily economic rather than technical. 



The geomorphic variability of the coast requires that a range of factors be 

 considered in the management and engineering of coasts for storm protection 

 and navigation. Environmental and geomorphic factors cause the rates, scale, 

 and nature of change in coastal environments to be highly variable, and the 



Chapter 6 Summary and Conclusions 



89 



