Those glorious inundations moved massive quantities of sediment through the Grand Canyon,wiping the slate dirty, and making a muddy mess of silt and muck that would make modern river rafters cringe.ĭo the following statements agree with the information given in Reading Passage? At less than 1,200 cubic metres a second, this flood is smaller than even an average spring flood, let alone one of the mightier deluges of the past. G Even so, it may turn out to be an empty gesture. So if a flood is going to do some good, this is the time to unleash one. The amount of sediment available is three times greater than it was in 2004. This time, the USGS is convinced that things will be better.
This problem was avoided in 2004, but unfortunately, on that occasion, the volume of sand available behind the dam was too low to rebuild the sandbanks. Eventually, however, the continued flow washed most of the sediment out of the canyon. The floodwaters built up sandbanks and infused the river with sediment. In 1996 the flood was allowed to go on too long. Floods were sent down the Grand Canyon in 19 and the results were mixed. Unfortunately, it is easier said than done. Meanwhile, aliens including fathead minnows, channel catfish and common carp, which would have been hard, put to survive in the savage waters of the undammed canyon, have move din.į So flooding is the obvious answer. These include the Colorado pike-minnow, the razorback sucker and the round-tail chub. In the years since the Glen Canyon dam was built, several species have vanished altogether. Without the cloudy water the chub became vulnerable.Į And the chub are not alone. The chub were well adapted to the poor visibility created by the thick, red water which gave the river its name,and depended on it to hide from predators. Steve Gloss, of the United States’ Geological Survey (USGS), reckons that the chub’s decline is the result of their losing their most valuable natural defense, the Colorado’s rusty sediment. But trout and chub co-existed until the Glen Canyon dam was built, so something else is going on. At first sight, it looked as if the reason was that the chub were being eaten by trout introduced for sport fishing in the mid-20th century. Recently, though, its population has crashed. The humpback chub, for example, thrived in the rust-redwaters of the Colorado. Even that has not been much use as those tributaries are not powerful enough to distribute the sediment in an ecologically valuable way.ĭ This lack of flooding has harmed local wildlife. These floods infused the river with sediment, carved its beaches and built its sandbars.Ĭ However, in the four decades since the building of the Glen Canyon dam, just upstream of the Grand Canyon, the only sediment that it has collected has come from tiny, undammed tributaries. Every eight years or so, that figure rose to almost 3,000 cubic metres. Spring Snow from as far away as Wyoming would melt and swell the Colorado river to a flow that averaged around 1,500 cubic metres (50,000 cubic feet) a second.
#BLUE FOOTED BOOBIES READING WITH ANSWER FULL#
By Thursday March 6th it was running at full throttle, which was expected to be sustained for 60 hours.ī Floods once raged through the canyon every year.
#BLUE FOOTED BOOBIES READING WITH ANSWER TORRENT#
That is why a man-made torrent has been surging down the Grand Canyon. Rivers – and the ecosystems they support – need floods. And a similar revelation is now – dawning on hydrologists. But foresters have learned that forests need fires to clear out the brash and even to get seeds to germinate. The flow of rivers is regulated by weirs and dams. People have, therefore, always sought to control them. While riverine flood damage can be eliminated by moving away from rivers and other bodies of water, people have traditionally lived and worked by rivers because the land is usually flat and fertile and because rivers provide easy travel and access to commerce and industry.Ī Fire and flood are two of humanity’s worst nightmares. Floods often cause damage to homes and businesses if they are in the natural flood plains of rivers. Floods can occur in rivers when the flow rate exceeds the capacity of the river channel, particularly at bends or meanders in the waterway.
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