Table 3-1. Estuarine problems. 



Due to navigation or 

 navigation improvements 



Not directly traceable to navigation 

 or navigation improvements 



Channel dimensions and layouts 



Shoaling 



Disposal of dredged material 



Salinity problems 



Erosion and deposition along shorelines 



Changes in regimen 



Pollution (heat, chemical, organic) 



Ecologic and environmental problems 



Jetties and groins 



Effects of landfills 



Effects of bridges and embankments 



Hurricane and storm surges 



Tsunami surge problems 



Diversion and changes of upland discharges 



Shoreline scour and deposition 



Pollution (heat, chemical, organic) 



Estuary ecology and environment 



Coastal marshlands 



Levees and dikes 



a particular prototype situation. It allows an investigator to study 

 various aspects of prototype behavior without observing and testing the 

 prototype itself. Although a model might not reproduce all prototype phe- 

 nomena, it must be designed to yield the desired design decision param- 

 eters (parameters on which decisions are based, such as tides, currents, 

 salinities, etc.). Basically, models are used as aids in the planning 

 process. In certain cases, model results may, within themselves, provide 

 sufficient information on which to base certain decisions; in other cases, 

 modeling may be only one step or a small part of the planning process 

 necessary to make a decision or develop a design (Simmons, Harrison, and 

 Huval, 1971). 



Estuary modeling is usually restricted to modeling water- related 

 problems where tidal action provides the major amount of system energy. 

 In some cases, other phenomena such as riverflow, wind waves, and storm 

 surges are of major importance, with tidal action merely a part of the 

 physical processes that control the system. 



Estuary modeling techniques have been applied to two major problem 

 types: (a) Predicting effects of construction in areas subject to tidal 

 action, and (b) establishing base-line conditions against which future 

 changes can be measured. Predicting the effects of changes caused by 

 construction has been the major use of estuary modeling. Establishing 

 base-line conditions in areas of anticipated changes has been a more 

 recent application which has grown from the need for guidelines against 

 which possible future developments may be compared (U.S. Army Engineer 

 Waterways Experiment Station, 1969). 



Modeling techniques are an important planning tool for a number of 

 reasons. It is both easier and faster to initiate changes and test their 

 effects in a model than in the prototype. The testing of many alterna- 

 tives in a model represents only a modest financial investment; prototype 

 testing of the same alternatives would probably be a prohibitively expen- 

 sive major undertaking. Prototype testing of tidal-related problems is 

 time consiaming, and often the results are of less than desirable quality 

 or quantity. It would be impractical to test a sufficient number of 



49 



