where Lj^ is the distance to the farthest point and d^ is 

 the average bay depth. 



(c) The inlet channel depth is large compared to the ocean 

 tidal range and the channel depth and width do not vary along 

 the channel. Hydraulic calculations may be made with a reason- 

 able degree o£ confidence if channel cross-section variations 

 exist but are not too extreme. For irregular jettied or un- 

 jettied channels, an effective channel length, L^ , which can 

 be used in place of L, is given by 



lih 



^a ^' 



Ac, 



Ax (6) 



where R and A^ are average values of the channel hydraulic 

 radius and cross-sectional area used in the hydraulic calcula- 

 tions, and R^ and A^^. are the hydraulic radius and cross- 

 sectional area at each of n sections of equal length. Ax, 

 spaced along the channel. For jettied inlets the length may 

 be taken as the distance along the channel axis from the sea- 

 ward end of the jetties to the section on the bayward end of 

 the channel where the flow velocity is diminished to a small 

 percentage [e.g., 20 percent) of the average channel velocity. 

 For unjettied inlets that are not too irregular in cross 

 section, the length may be taken as the distance along the 

 channel axis between the points on each end where the veloc- 

 ity is, for example, 20 percent of the average velocity. 



(d) Bay walls are vertical over the bay tidal range. 

 Hydraulic calculations may be made with a reasonable degree 

 of confidence if there is no extensive flooding of tidal 

 flats. 



(e) There are negligible density currents at the inlet and 

 negligible inflow to the bay from other sources (rivers, over- 

 land flow, precipitation, etc.). 



The values for kg^, kg^, and f must also be established for 

 calculations to proceed, kg^ may be assumed equal to unity (kg^ = 1.0) 

 and kg^ will probably vary between approximately and 0.2 as the 

 entrance hydraulic efficiency decreases. A value of kg^ = 0.1 is 

 recommended for most calculations. 



The friction factor, f, or Manning's n (n = 0. 093R^ ''^f ^ ''2) depends 

 on the bed roughness and flow velocity. For a sandy channel bottom 

 typical of most inlets, f can vary between 0.01 and 0.07 depending on 

 the peak velocity and the phase of the tidal cycle. If no information is 



