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Name: Kevin
Status: Student
Age: 6-8
Location: FL 
Country: United States
Date: October 2, 2005


Question:
I am researching different things that cause erosion and am specifically looking at the effects of saltwater on erosion. Does saltwater cause erosion in a way that is different from fresh water?
I am not looking for information on intrusion, just erosion. I am wondering if the process is too slow for anyone to notice it or understand it.



Replies:
Erosion is not a simple process to model. In addition to the flow rate of water, the chemical composition of the soil/rock comes into play. The pH and ionic strength play a role, but whether these factors increase or decrease the process depends upon the composition of the soil/rock. The granular structure of the soil/rock is important and is mineral-dependent. Some minerals are "compacted" by water making them more difficult to further erosion; others are "loosened" making them easier to further erosion. The vegetation (or lack of/ type) also has an important effect. So just how hardy the plant life is in fresh vs. brackish vs. salt water is a major factor. Erosion is also a function of the flow rate of the water and this effect is not linear. For example, erosion may be negligible for flow rates up to a certain critical value and then becomes very rapid and non-linear. This can result in a "land slide" which is the ultimate erosion process. The chemical interaction of the soil and water plays a role -- that is, certain minerals in the soil may be soluble in the water resulting in chemical breakdown of the soil. In short, erosion is a very complicated phenomenon to model, and extract the effect of fresh water vs. salt water from all the other interacting variables.

Vince Calder


Kevin,

When it comes to this kinds of things I always try to reword the question so that I can better answer it. First of all, what is the main difference between salt and fresh water? Once you answer that, then the question becomes, is the difference quantitatively large enough so that you can expect a different form of erosion. Finally, since you want to discount intrusion (which I take to mean that you want to discount physical activity of the body of water as opposed to the quality -salt or fresh- of the water) as a factor in erosion, then that really limits you to whether the main components of land mass is more soluble or easily mixed in salt or fresh water. I think, you can take it from there.

Greg (Roberto Gregorius)



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