No, this isn't for school, but I'm really interested in knowing what the immediate benefits of dredging rivers and lakes etc are. Is dredging reversible? Would it be better to dredge a river, or to leave it in it's natural state?
2007-05-17 11:55:33 · 5 answers · asked by madeline b 3 in Environment ➔ Other - Environment
The positive affects are now apparent, but I'd like to know more of the negative affects. Why did my local river turn brown when it was dredged? Will it ever go clear again?
2007-05-17 14:03:38 · update #1
It was dredged in 1960 something. I'm pretty sure it had time to settle by now, it's not, any other ideas?
2007-05-21 12:18:09 · update #2
The immediate benefits are usually:
1. Increasing or maintaining the depth of the water so it remains navigable
2. Harvesting sand for construction projects or to reconstruct or restore eroded beaches
3. Maintain waterways to guard againts erosion and help with flood control.
4. Removing trash and debris
These are important benefits, but since dredging does always have an impact environmentally and commercially (it's not reversible), the benefits and risks should always be weighed.
But as long as we use our national waterways for pleasure, commerce and transportation, dredging will be necessary. Measures should be taken to at least limit the amounts of toxic chemicals released, and also to time the dredge so as not to disturb spawning and other reproductive activities of the native species.
There are lots of different dredging methods and the one with the least negative impact but with the greatest benefits should be used.
2007-05-17 12:08:53 · answer #1 · answered by Veritas 7 · 1⤊ 0⤋
The river went brown because of all the sediment which was stirred up by the dredging. The water will clear as the sediment settles.
Rivers which contain contaminants on the bottom can be negatively impacted by dredging. The contaminants, which were lying dormant, are stirred up and set loose by the dredging action. This releases them into the water and makes the pollutants more "active".
2007-05-21 15:02:35 · answer #2 · answered by steve d 4 · 3⤊ 1⤋
Dredging is the most proven and effective technology for cleaning up contaminated sediments. Environmental dredging techniques remove the source of contamination and reduce contaminant concentrations in sediment (and, over time, in fish).
Monitoring data for cleanups at other PCB contamination sites show that cleanups were able to reduce the total amount of PCBs by more than 90%, reduce concentrations of PCBs in sediment by at least 82%, and reduce the PCB concentrations in fish by at least 56%.
In other river systems where dredging has occurred, levels of PCBs in fish have dropped substantially within just a few years.
Environmental dredging techniques differ markedly from the open "clamshell" dredging that GE has depicted in its TV ads. Cleanup dredging often uses hydraulic or suction technology to remove sediment with great precision, and is designed to minimize the amount of sediment that is stirred up, or re-suspended, into the water.
The amount of stirring caused by hydraulic dredging is generally not greater than the amount stirred up by the normal river flow.
2007-05-17 19:12:21 · answer #3 · answered by Song 6 · 1⤊ 0⤋
on the other hand.... dredging upsets the ecosystem and all of its inhabitants by destroying their habitat. this can lead to a domino effect as species scramble to compete in a new environment and some will win and some will become extinct.
dredging impacts the natural flow of a riverway which can impact a river's ability to cleanse itself of upstream pollutants and, if close to saltwater, increase saltwater intrusion which can impact both the aquatic and soil systems in the area.
it increases boat traffic and all the attendant oil leakage and damage to resident species - manatees are a good warm water example.
2007-05-17 19:18:38 · answer #4 · answered by Basta Ya 3 · 0⤊ 0⤋
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2007-05-23 06:49:12 · answer #5 · answered by BRAINY SKEETA ® 6 · 0⤊ 0⤋