1990; Clausner, Patterson, and Rambo 1990). 



164. The problem of scour in the inlet, however, still remains and is 

 the subject of ongoing studies. In 1940, the channel depth was approximately 

 20 ft. At present (December 1990) the inlet throat averages over 40 ft in 

 depth and contains three large scour holes. One scour hole, located near the 

 tip of the jetty, has caused loss of part of the north jetty. The other two 

 scour holes are in the vicinity of the bridge pilings where the depth reaches 

 more than 80 ft along certain sections . 



165. One of the basic questions to be answered is why the rate of scour 

 increased in the period 1974 to the present as compared with the time 1934 to 

 1974. Several factors are under evaluation, such as different layers of 

 material composing the underlying sedimentary structure, changes in jetty 

 configuration, and mining of the flood- tidal shoal. Whatever the cause, the 

 capability to quantitatively predict tidal flow through the inlet is required 

 to arrive at a process-and-response understanding of the sediment transport 

 regime at the site. To this end, the Coastal Engineering Research Center 

 (CERC), in support of the USACE District, Philadelphia, collected tidal 

 velocity data for conducting a comprehensive two-dimensional hydrodynamic 

 numerical modeling effort. 



166. The Indian River Inlet channel is relatively narrow and long, and 

 the tidal flow in it is expected to be well described by a one -dimensional 

 hydrodynamic model. Also, current velocity data taken in the shallow natural 

 channels connecting Rehoboth and Indian River Bays, as well as tidal elevation 

 measurements made in the bays at intermediate and far distances from the 

 inlet, make the site highly suited for testing both the accuracy of a one- 

 dimensional model and its capability to represent boundary conditions in 

 complex bays represented by multiple channels. 



167. In the present study, tidal flow and elevation data obtained for 

 the more extensive hydrodynamic modeling effort presently in progress at CERC 

 were used to examine the predictive capability of DYNLETl . A description of 

 the data collection effort, associated hydrodynamic modeling, and results 

 pertaining to the aforementioned scour problem can be found in McGehee and 

 Lillycrop (1989) and Anders, Lillycrop, and Gebert (1990). The measurements 

 processed for use in the ongoing two-dimensional modeling effort were used 

 directly in the present study without modification. 



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