COASTAL HYDRAULIC MODELS 

 I. INTRODUCTION 



-by 



E.Y. Hudson 



1. Purpose and Scope . 



This report provides information on hydraulic scale models of coastal 

 engineering problems for design engineers to properly evaluate the useful- 

 ness of such models as an aid in obtaining practical solutions to diffi- 

 cult coastal problems. Sufficient information is presented so that the 

 state-of-the art of scale modeling of the most important types of coastal 

 problems can be discerned. These problems include: (a) the effects of 

 wind waves, long-period seiche-type waves, tsunamis, wind setup (storm 

 surge), and astronomical tides on currents and sediment movement in the 

 coastal zone and estuaries; (b) the functional efficiency of coastal 

 structures; (c) the effects of coastal structures on littoral currents 

 and beach erosion and accretion; and (d) the stability of coastal struc- 

 tures when subjected to the forces of waves and currents. The structures 

 considered, and the natural forces to which they are subjected, are those 

 that are pertinent to navigation, beach erosion, sediment transport and 

 deposition in estuaries, pollution, and the control of wave-generated 

 flooding. Coastal problems are discussed under the general headings of 

 estuaries, coastal harbors, coastal erosion, stability of coastal struc- 

 tures, and inlets. Hydraulic scale-model technology, considered as an 

 engineering tool, is discussed with respect to (a) its historical develop- 

 ment; (b) similitude relations; (c) field data required; (d) model design, 

 operation, and interpretation of results; (e) application, advantages, 

 and disadvantages; and (f) general time and cost estimates for typical 

 model studies. 



2. Historical Development of Hydraulics and Scale-Model Techniques . 



Although there is evidence that the control of water through canals 

 for irrigation purposes occurred in several parts of the world (e.g., 

 Egypt, Mesopotamia (mostly present-day Iraq), India, Pakistan, and China) 

 nearly 5,000 years ago, the study of hydraulics in a scientific manner was 

 actually begun by Leonardo da Vinci, in Italy, about the year 1500 (Rouse 

 and Ince, 1957). The first known scale-model experiments were conducted 

 by an English engineer (John Smeaton) during the period 1752-53, to deter- 

 mine the performance of water wheels and windmills; a French professor 

 (Ferdinand Reech) in 1852, was the first to express what is now known as 

 the Froude criterion of similitude (Rouse and Ince, 1957). The earliest 

 known tests on a movable-bed river model were conducted by another French- 

 man (Louis J. Fargue) in 1875 (Gibson, 1936; Rouse and Ince, 1957; Ippen, 

 1970). In Fargue 's tests the model riverbanks were fixed and sand was 

 spread over the bottom. The depth scale was 1:100, and the width and time 

 scales were arbitrarily assumed. In 1885, tests using a movable-bed model 



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