140 



LANDSCAPE DESIGN 



Streams and 



Stream 



Banks 



Whenever an along-shore current is bearing sand or other fine 

 material with it, if there is a slackening of current, there is a deposition 

 of the drift material which it carries, and so any sheltered cove, or the 

 sheltered side of any promontory, would tend to have its own sand beach, 

 and on the downstream or down-current end of promontories there 

 would tend to be a sand spit. If the conditions remain constant, 

 there will come a time when a beach will protect itself against wave 

 action, having assumed a constant slope, and except for the effects 

 of great storms or high tides which send the waves to attack the slope 

 behind the beach, a beach may remain in the same place for ages even 

 under the assaults of the ocean surf. 



A typical shore modeled by wave-action from mixed materials of 

 various sizes would thus have its promontories made of the coarser and 

 more tenacious material standing at a steeper slope both in the bank 

 and on the beach, and probably with some outlying bowlders on the 

 beach and in the water. The form of the promontories would be 

 more or less rugged, expressing the structure of the wave-resisting 

 material of which they are made. Between the promontories and in 

 other sheltered places might be beaches of gravel or sand, flatter in 

 slope and falling into curved lines expressing the submission of the fine 

 material to the forces of the waves and currents. 



The valley of a stream and especially its immediate shores express 

 by their forms the work of the flowing water to which they owe their 

 origin. 



Near its head-waters, the work of a brook is almost entirely cutting, 

 and the ground forms show this. Where a current is cutting a bank 

 of mixed material, naturally it cuts at the bottom, carrying away what 

 it cuts, and the form of the bank will be produced by gravitation and 

 the work of rain, which carry the material down into the stream. The 

 more tenacious the ground is which the brook is eroding, or the larger 

 its component particles, the steeper will be the banks which the brook 

 produces. Any particularly large fragment of stone will resist the cur- 

 rent and perhaps serve as a protection to weaker material behind it. 

 On the other hand, a bowlder standing in the stream will tend to concen- 

 trate the erosive power of the water where the current strikes it, so that 

 above it and on each side of it the bottom of the stream may be scoured 



