A New Navajo Art

Sand Waves

The Colorado river was unusually high in the spring of 1942 when Dr. Russell G. Frazier, Willis Johnson and I launched our three small rubber boats at Dandy Crossing to float down through Glen Canyon to Lee's Ferry, 180 miles below; but since high water had obliterated many of the riffles and smaller rapids found at low water we anticipated no difficulty. Except for floating logs and small driftwood the wide, muddy stream was almost as smooth as a millpond as we floated along at about eight miles an hour, enjoying the magnificent canyon vistas revealed at every hand. After three days of this tranquility it appeared our voyage might be lacking in adventure. But the Colorado is never twice the same and although we had passed through this canyon several times, it had something new to show us. Just after passing the mouth of San Juan river, coming in from the east, we stopped to examine the smooth sandstone walls for Indian petroglyphs and possible early Spanish inscriptions. As we reached the top of a high sand bank we heard a low rumble which gradually increased to a deafening roar, echoed and magnified by the perpendicular canyon walls. Startled, we looked back at the river which had been flowing quietly only a moment before. Its surface, from bank to bank, was corrugated by heavy, closely spaced waves formed at right angles to the current. While we watched the waves rose higher and higher until they began to break upstream against the current, one after the other at regular intervals, making a roar like a mighty rapid.

"What goes on?" Dr. Frazier asked, fascinated by the strange sight. "There's no rapid here, and the river was quiet when we left the boats."

"Sand waves!" I replied, hazarding a guess.

"Sand waves?" Johnson queried. "What causes 'em?"

I couldn't answer that, although I thought I recognized their peculiar form from a description given me by Bert Loper, old time river man. Although this was our fourth voyage on that section of river, none of us had ever seen a sand wave. A good many voyagers, including Major Powell in 1869, have passed all the way down the Colorado without seeing one. They appear to be peculiar to this great desert river and one or two of its larger tributaries.

We had planned to visit Music Temple, directly across the river, where members of Powell's two expeditions had carved their names; but the choppy, roaring waves made us hesitate. Then, as we stood debating our next move, the waves disappeared as suddenly as they had come, leaving the river once more smooth and quiet.

"Come on, boys!" Doc yelled as he raced for the boats.

We pushed off again and began pulling for the opposite shore, but before reaching the middle of the stream sand waves began to form again. They started as a mere ripple, but within a minute or two were six feet high and breaking backward into the boats with a peculiarly terrifying growl. Because they were spaced so closely together it was almost impossible to use the oars. First the boat stood on end, then balanced on the crest and finally dived into the deep trough. We had a wild ride for a half a mile before being thrown into an eddy where we managed to pull to shore, sustaining no other damage than a thorough wetting.

From there all the way to Lee's Ferry we encountered an almost continual succession of sand waves, which gave us an unusual opportunity to study their action. It is possible we may have discovered their cause; at least we are prepared to advance a theory.

Unlike ocean waves, which are caused by and travel with the wind, sand waves remain in a fixed position in relation to the river bank. Beginning as small corrugations on the river's surface, extending often from bank to bank, they quickly increase in height until in places they seem to be ten or twelve feet from trough to crest. Then the crest breaks, upstream, like a breaker on the beach, causing a heavy and continuous roar as the waves break, one after the other in regular succession. When the whole series has broken it may repeat the performance or disappear entirely for a few minutes before reforming. Sand waves occur below the mouth of any tributary which carries an unusually heavy load of silt, like the San Juan, and continue until this overload has been deposited on the bottom.

By Charles Kelly

Our observations lead us to believe that because of its density and weight this overload of silt causes a drag on the river bottom. The lighter surface water, being more fluid, tries to flow at a greater speed, setting up a sort of friction with the silt laden strata near the bottom. To illustrate this action take two strips of thin dental rubber; stretch the lower strip, wet its surface and lay on a second strip without stretching. When tension is relaxed on the lower strip the upper piece will form corrugations exactly like sand waves.

Some river men believe sand waves are caused by corrugations of the river bed, the water following these unseen ridges. We found, however, that the waves occur in water sometimes forty feet deep where any such conformation of the bottom could have no effect. We were unable to determine why the waves appear and disappear at intervals, unless the difference in "tension" between layers of light and heavy water accumulates and dissipates in periodic surges. In some places, however, the waves remain practically constant until the load of silt has been dropped, particularly where the current is swift or the channel narrow.

We camped that night on a sandbar below Music Temple and at the head of another big series of sand waves. All of us had slept beside roaring rapids in other parts of the river and were accustomed to the sound, which is constant and soon puts one to sleep. But sand waves were entirely different. As they formed they made a swishing sound which gradually turned to a low rumble, increasing in intensity until it sounded as though the canyon walls were about to fall on us. After a few minutes the roar decreased until at last perfect quiet reigned. This was repeated over and over all night long, and it was many hours before we finally went to sleep.

Continuing downstream next day we attempted to keep our boats on the inside curve of the innumerable river beds in order to avoid the almost continuous succession of sand waves in the main channel. Sometimes we were successful, sometimes not. Eventually we quit worry-ing about them and rather enjoyed the excitement of be-ing tossed about for half a mile every now and then. It was something like riding a long roller coaster.

But our carelessness ended in disaster. Just above Wildhorse bar we suddenly ran into a rapid caused by a big rock fall, where the whole flood passed through a narrow opening choked with great boulders. To com-plicate matters heavy sand waves were running at right angles to the waves of the rapid, and these, the biggest we had seen, were breaking upstream with a menacing roar. It was a nasty looking place and we were into it before we realized what was happening. Frantic pulling on the oars got us nowhere, as our small inflated boats were tossed about like bits of driftwood. There was nothing to do but go through and trust to luck.

Doc Frazier, who was heavy on the oars, managed to avoid the biggest waves and got through with nothing more serious that a boatful of muddy water. Johnson, next in line, was drawn into the main current where a big, roaring sand wave turned him neatly upside down. After what seemed several minutes he came to the sur-face and clung to his overturned boat, then went out of sight around a bend.

Following not far behind, I ran into the same wave, which turned my boat on end and dumped me out. For-