PART VI: EXAMPLE APPLICATION 2: INDIAN RIVER INLET, DELAWARE 



160. This chapter presents an example calculation demonstrating the 

 applicability of DYNLETl in tidal flow studies involving a bay (in this case, 

 two bays) and a narrow inlet throat at Indian River Inlet, Delaware. 



Indian River Inlet 



161. Indian River Inlet is located approximately half-way between Cape 

 Henlopen at the entrance to Delaware Bay and the State line of Maryland. It 

 is the only inlet in the State of Delaware (Figure 12) and the only opening to 

 the Atlantic Ocean for Indian River Bay and Rehoboth Bay. Both bays are 

 shallow, with an average depth of approximately 7 ft (Anders, Lillycrop, and 

 Gebert 1990). Historically, this inlet was an ephemeral feature that inter- 

 mittently opened to expose Rehoboth and Indian River Bays to the Atlantic 

 Ocean. During flood tide, the flow goes through the main channel, under the 

 State Highway 14 bridge that spans the inlet, and then splits into Rehoboth 

 Bay and Indian River Bay. Thus, the system consists of a well-defined main 

 channel and two bays . 



162. Between 1938 and 1940, the USACE constructed two rubble -mound 

 jetties that stabilized the inlet, thereby maintaining water quality and 

 allowing free navigation between the bays and the ocean. The jetties are 

 500 ft apart, and two sets of pilings from the Highway 14 bridge are located 

 in the inlet channel. Upon construction of the jetties, the navigation 

 channel was 200 ft wide and 14 ft deep. 



163. The coastal area around Indian River Inlet has experienced three 

 problems of engineering significance (Anders, Lillycrop, and Gebert 1990): 

 scour in the inlet, particularly at the tip of the north jetty and adjacent to 

 the pilings of the bridge along Delaware Highway 14; erosion of the shoreline 

 interior to the inlet; and erosion of the beach to the north of the jetties 

 (with corresponding accretion on the beach south of the jetties) . The last 

 two-listed problems have been substantially mitigated and are effectively 

 under control, with the interior shorelines now protected by bulkheads and 

 revetments, and the imbalance in longshore sand transport at the jetties 

 appears to be corrected by a successful sand bypassing operation (Clausner 



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