2. River Mouths. The area on either side of a river just upstream from its mouth has certain 

 advantages as a site for a small-craft harbor (Fig. 2). The river current is often minimal, and 

 the site is usually protected from ocean or lake waves. Also, the river has usually scoured a 

 deep channel that may be adequate for navigational access. However, the site may be 

 endangered by occasional river floods, and sediments moved by river currents or tidal action 

 may shoal the harbor basins and channels. Much depends on the characteristics of the river: 

 whether it is relatively slow -flowing and stable; has a steep gradient and is subject to flash 

 floods and channel meandering; and if the sediment load may be transported into the water 

 areas of the harbor. These factors require in-depth study by quahfied coastal engineers. At 

 times, the river flows through a delta estuary or marshland before reaching the ocean or 

 lake; then the harbor can be situated in a basin and isolated from the main flow of the river. 

 This type of river-mouth site is safer from direct flood damage, but the channel leading to 

 the harbor from the main flow of the river may be subject to shoahng by river floods. 



3. Dredged Lowlands. Low, marshy areas are often found adjacent to ocean and lake 

 shores where no river exists. Ecological factors permitting, these areas are good sites for 

 small-craft harbors (Fig. 3). Marshes can usually be dredged to navigable depth at reasonable 

 costs. If the dredged material is suitable, it may be used to fill perimeter areas to design 

 levels for roads, parking, and other harbor-support uses. Although the low cost of using this 

 marginal land may be attractive, this advantage may be offset by the high cost of 

 maintaining an entrance to navigable waters in the lake or ocean if the rate of longshore 

 movement of Uttoral material is high. Protection against shoahng due to httoral drift is 

 possible by using various methods. If the longshore transport is predominantly in one 

 direction, provision must be made for sand bypassing (discussed in Sec. V). If the shore of 

 the lake or ocean is frequented by high waves, protective structures may be required to 

 reduce surge and wave action in the entrance and interior basins, as discussed in Section IV. 

 There are advantages to siting an ocean harbor opposite the head of a submarine canyon. 

 The deep water of the canyon refracts waves toward its flanks, making the canyon head a 

 relatively calm area of wave divergence. Thus, the harbor is ensured not only of a deep, 

 maintenance-free channel, provided httoral transport is excluded, but a minimum of wave 

 energy penetration into the berthing basins. The need for adequate exchange of water in a 

 dredged interior basin to preserve its quality may be another important factor. 



4. Bays. Some natural embayments provide excellent sites for small-craft harbors (Fig. 4). 

 However, the mouth of the bay should be small or protected by islands to exclude most 

 waves from entering the bay from open water. Preferably, the bay should be small enough 

 so that waves of undesirable heights cannot be generated by winds within the bay's confines. 

 In a large bay, some type of protective structure may be required to exclude larger, locally 

 generated waves from the berthing areas, or for secondary protection from large storms. 



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