A lot of water over a little time or little water over a long time?
That was the geological hot-button in the late 18th century through the beginning of the 19th. Before the advent of uniformitarian thought in the West, most geologic structures in the Western Christianity were interpreted through a Young Earth & a recent Global Flood lens.  Though the specifics were not known, this was the general way of thinking because the people, including the scientists (like Newton), took the Bible as the ultimate authority source, especially during and after the Reformation.  Now they knew that the Bible did not go into detail on such issues, but the historical reality of the Flood would leave reminders.
However, as the Scripture was being attacked by humanistic thinking on theologic and philosophic grounds, it was also being attacked on historical grounds.  When the history of the Bible in Genesis was denied, a wide range of emerging scientific philosophies took root. The predominant view popularized by Charles Lyell in the 19th century was uniformitarianism. Uniformitarianism is the scientific model that the present is the key to the past–i.e. most geologic structures are formed slowly over eons of time.  However, Lyell was no mere unbiased objector of the truth.  On the contrary, not only was he a rabid anti-Christian, he pushed his philosophy of uniformitarianism with great veracity, and many people bought into it. Alleged great eons of time was now theoretically available to then push the molecules to man evolution, and this is exactly what spearheaded Darwinian thought several decades later. Macroevolution (molecules to man) was already being propagated, but Darwin could popularize the teaching because of Lyell’s time scale.
We deny that the earth is billions of years old and uphold the Global Flood because of our commitment to Scripture.  Nonetheless, how has this theory of uniformitarianism stacked up in the scientific community?  Not to our surprise, many evolutionary scientists themselves deny that the earth has come to be slowly one sand grain at a time by one drop of water at at time.  Though most of them believe the earth is old, due to other philosophic assumptions they make, they do acknowledge that the geologic layers are filled with catastrophe.  Mass fossil graveyards are interpreted as occurring through catastrophic events.
We should not be surprised when we see evidence for a global catastrophe because that is exactly what is recorded in Scripture, primarily through the Genesis Flood.  We interpret such catastrophic layering, fossil formation, mountain building, and canyon erosion through the lens of Scripture.  Much of the upper level topography that we observe today is best interpreted as being caused by the Flood or by post-Flood events like the Ice-Age and subsequent smaller local scale catastrophes.
As for geologic structures like the Grand Canyon, we can best understand them through Biblical glasses. Only the Scriptures give us a reliable lens to interpret the world, and, though our scientific models are modified at times, the general creation model itself is sustained by Scripture.  Though it is difficult do delineate exactly what may have been formed during creation week and what has been formed after that through the Flood, we can get a general idea.  Much of the upper layers of the canyon are formed through rapid sedimentation laid down by water.  We can see this through ‘bent layering’, which is to say that we see many layers flowing together and then bent in one or many directions while still soft.  This must of have occurred rapidly while soft; otherwise, the layers would have been crushed upon themselves.
As for the canyon itself, it is likely that it formed after the layers had been laid down during the Flood. Sometime before and at the end of the Flood or most probably after the Flood, giant inland lakes once existed in that area (as understood through topographical scars of such lakes).  There was a breached dam of some sort, it appears, and this could have occurred at the end of the Ice Age.  As the glaciers began to melt, large quantities of water would fill these lakes by means of rivers and such.  Eventually the lakes would have overflowed, and a water pouring out by means of a massive catastrophic breached dam would have carved out the Grand Canyon.
The Bible had it right all along! Amen!