TIDAL BORE

The delta of the Colorado River is a swamp, a desert, a salt flat, a mud bank. The delta is a burning sun and a red river. It is cotton, mesquite, ocotillo and cholla. It is the nothingness of the Laguna Salada.

It has a mountain range on one side and a desert on the other. To the south, it has the blue waters of the Gulf of California; to the north, the Salton Sea, over two hundred feet below sea level.

The delta is the Grand Canyon transplanted south of the border. It is a dike holding the Gulf out of Southern California. It is a barrier of bottomless silt.

Buffeted by wind and baked by the sun, assaulted by waters, the earths of the delta are in constant movement. From desert to mud bank to sand bar to dune. And through some of the earth creeps the white crust of salt.

The delta is a mingling of salt water and river water. Forty miles up river go the saline waters of the gulf. The river roars with the coming of the gulf waters. The banks of the river crumble against their attack. The sloughs, the gullies, the creeks, the flats are filled with sudden water. For the delta has its own phenomenon-the tidal bore.

The bore is a wave and it is more than a wave. It is a bank of water extending in huge breaking turbulence across the wide river. It is white-crested water moving swiftly. It is the greater part of the flood tide advancing not minute by minute, nor foot by foot, but all at once.

The bore is a tumult, an uproar, a rumble of change. It is the great flood tide of the gulf held at the river's mouth until it grows strong, until its forces are greater than the obstacles-the shoals, islands and sand bars in the mouth of the river-and with majesty and greatness and power and rage it roars up the channel.

But the channel cannot hold the surging tide and the delta is flooded. The deserts become lakes, and the vast sterility of the Laguna Salada fulfills the promises of its summer mirages and is flooded.

In the fall of the year the tides of the gulf hump high toward the full moon of the September equinox. It is the time of maximum tides-the apex of the water's surging. As much as eighteen feet is added to the normal tidal range of thirty-two feet at the head of the gulf. It is the time of the greatest bores.

The "plaza" of San Felipe, Baja California, becomes a lagoon during the spring tides. During the Equinoctial tides, flood waters reach to the very doorsteps of the buildings. The natives of this village are fishermen.

When the "burro" is running, white pelicans rise nervously from the mud flats as they sense its approach. Beaver and muskrat are safely in their burrows. Herons, cranes and swans lift gracefully out of the flooding marshes. Only man has trouble in the lower delta. There is little high ground for him to find safety on.

But there is some. La Bomba is one such place. La Bomba is abandoned now, its customs men gone to Mexicali or Mexico City. The traffic in smuggling Chinese aliens for cheap labor in the cotton fields of Mexicali is no longer profitable.

La Bomba is twenty-one miles up the river. It is a good place to see the bore if you can get there. Go overland, make your own road across the desert in the winter, the spring, the summer, when the bore is moderate and the desert is crusted by a burning sun. But not in September or October, when the bore is truly worth seeing and the desert is soft and treacherous and its gluey mud holes bottomless.

In October, go down the river-down from the fishing camps at El Mayor, where the chimneys of camp sites stand in the September flood water like ancient relics of a lost time-or down from the ferry crossing, seventeen miles north of La Bomba.

At the ferry find the truckers, the families, the children who live in the heart of the delta and work its cotton. Watch the swift ebbing of the water as the ferry is hauled back and forth across the river by the brown arms of manpower. See the mud banks lengthen as the time for the flood tide approaches.

"Burro? Si, Señor. The big one. It comes soon." The dark heads of the Mexicans nod in agreement. So talk with a man who knows a smattering of English and learn that during the September high tides the land between the El Mayor range and the Sonora shore went under water, only the tops of its trees breaking the sweep of the vast, sudden lake of tide water.

Learn that the ferry, immobile during the flood, was temporary home to the ferry-keeper and his family; that other isolated families walked in constant water while their chickens and livestock died from lack of forage.

Talk with a young Mexican helping his wife bait a

fishing line with a grasshopper and learn that he was west of the river when the flood came and that she was east of the river. It was three weeks before he could get home.

So wait at the ferry for the surge of the bore and see it bring five feet of the flood tide in the moments of its passing. See the mud flats disappear and the water spread over the banks of the river in the following minutes, and know that down river the bore is much, much stronger, for momentum and force are lost in the twisting channel.

Then wait again for the three hours and more of the flood tide so you can start down river on the ebb, and think about what you have seen so far.

Think about cotton. dead cotton flooded when the gulf tides held the river's waters on the land until the canals and ditches overflowed into the fields Of the reflections of the cotton in the still standing water, broken by the splash of leaping mullet.

Think of the mingling of fresh water and salt water and the white death of salt that will be left on the land. Of fields planted with hope, abandoned with despair. Sit in the shade and fight the mosquitoes and wait for the turn of the tide.

When the tide begins its ebb, push off from the bank in your small boat. Leave your car in what you think is a safe place and hope you will be lucky enough to get back to it without trouble. The river does not welcome sightseers.

Paddle just enough to keep out of the eddies. The river will carry you six knots an hour past an abandoned farm house with the water lapping at the front door, past a flooded field of cotton with the plow and tractor still in the field.

Into the river pour tiny, swift waterfalls-the ebb tide leaving the flats. Into the river fall trees from the river's banks, their roots loosened as the swiftly ebbing water snatches the earth of their sustenance.

The trees crash into the river and go end over end toward the gulf to be abandoned on a mud bank by the tide and there be caught in the rush of the bore and carried up river again. Back and forth journeys the debris of the river in the flux of water.

In the dense foliage along the channel, cattle and horses bog through the mud and water after forage. Drowned cattle circle in the eddies, are caught by the current and carried on. A tree crashes into the river and keeps pace with the boat. The conformation of the tree is peculiar and easily recognizable.

Before the hot sun goes down, an almost-full moon is visible in the clear sky. The coming night grows brilliant with white moonlight. Three hours and fifteen minutes after leaving the ferry, be carried past what you suddenly realize is a patch of dry ground on the high river bank!

See a slough opening into the bank near the dry land of the bluff-a perfect anchorage for the boat when the bore strikes-and be carried past it by the urgent tide!

So fight the tug of the racing ebb. Fight to turn the boat into the slough-and fail. Sixty feet later ram the boat into the mud bank, take a bow line over the side and step into mud over your knees. Climb the slippery bank to still muddy flat-land and tow the boat to where a tree is holding in the bank at the edge of the slough. Use the tree for anchor while the bow line is taken down one side of the slough and up to the higher bluff of the opposite side. Feel dry earth under your bare feet at last.

But the river would still claim the boat. A tree has fallen across the mouth of the slough and no amount of tugging or pulling or hacking of branches will budge the weight of the tree or help get the boat past it to safety.

So lay the wagers on a gamble-your skill in timing against the rush and fury of the bore. The moment of swift action when the stope of the wave would lift the boat and it could be pulled over and past the fallen tree-or lost. It is a gamble without the alternative of being refused.

Secure bow and stern lines on the high side of the slough and slip and slide in the black mud while supplies and cameras are unloaded in the bright moonlight. Eat a belated supper. Relax, but do not sleep, for the bore is due at midnight. Gather cow dung for the fire and watch distant herons feeding on the mud flats. Wait, and worry about the boat.

The river is noisy with the crashing of its banks into the water. Great blocks of earth topple into the river, leaving the roots of the trees exposed until they, too, fall. Pace off the high ground of your camp and find the bluff seventytwo yards long. Mark numbered feet back from the edge of the bank to judge the erosion during your stay. See the rutted tracks of a car ending abruptly in space.

A resounding crash sends you running to the slough to find that the tree on the opposite bank has fallen into the river, barely missing the boat. There would have been no saving it had the boat been torn from its moorings by the falling earth or the trunk of the tree. Even as you turn back to the camp site, you hear the roar of the approaching bore.

The noise is a booming, a distant thunder continuing for thirty minutes and increasing to a reverberating roar as the white crest of the bore flashes into view around a distant bend in the river. Break the paralysis of your amazement at the approaching storm of water and stand ready with the lines from the bow and the stern of the boat. On the instant the stope of the bore raises the boat, bring it into the slough fast and miss the churning tumult of the breaking crest.

Then give way to your amazement as the turbulent water crashes against the banks and engulfs the mud flats. The slough is passage to the desert behind the bluff and in minutes holds eight feet of water where there had been eighteen inches. The water sweeps over the lower land at the other end of your dry ground and you are surrounded. The bluff is an island. The river is lost in the reaches of the spreading water. The tree which followed you down river and came up on a sand bar opposite your camp is poling end over end in the chaos of the bore's advance.

Finally, try to sleep and find excitement still rampant and sleep elusive. Brilliant moonlight shatters against the still rising water. Tomorrow will bring the bore in daylight. MañanaMorning brings a burning sun, an enervating suffocation of dazzling heat. So erect a shade from your supplies and sip the drinking water you have brought with you that teases but does not quench your thirst.

Morning brings the ebb tide (and the same tree is back on the same mud flat). And morning finds you a prisoner, inexorably bound to the dry bluff by the vast, impassable reaches of mud.

As far as you can see, the delta is heavy with the weight of saturated mud and littered with the debris of its ruined vegetation. The delta sun is blazing, sickening heat. Thunder clouds form over the distant mountains of the Sierra de Juarez and there drop the cooling, healing rain. Evaporation is rapid in the burning, drawing heat. Taste the salt

drawn from your body. Salt in the flooded soil will remain in the earth like a corroding memory when the delta has dried and cracked under the blistering sun.

So sit under shade and listen to the river undermine its banks, and know that even as you wait, the bore is making up in the mouth of the river.

The bore begins on the last of the ebb, and rolls in over the still running ebb tide. There is no slack water in the mouth of the river. The bore begins in patches of broken water moving aimlessly back and forth across the river. It is a growing uneasiness of undirected pressure, an increasing restlessness of potential power. It is broken water gathering into a stationary roller extending across the river's mouth.

The pressures of the flood tide from the gulf increase behind it. The roller grows stronger. The roiling water becomes steep fronted. When the great tide can no longer be held back by the racing ebb, by the sand bars and the islands which obstruct it, the front edge of the roller breaks and the bore begins to move up the channel, rapidly gathering strength and size and speed.

The steep, high stope of the bore crashes tumultuously against the broken shoreline, and in constricted turnings of the channel is concentrated upon itself in swelling power and force. There is a powerful swinging from one side to the other as the surging flood races up the channel-a whipping corkscrew of moving, thundering water.

Time the speed of the bore as it races past the bluffmore than twenty-one miles from its genesis-and find it runs the seventy-two yards of the bluff in six seconds!

The powerful backwash of water surging away from the bluffs, after the sudden onslaught, crisscrosses the river with white-crested currents, is caught by the following surges of the bore and in a few minutes the heaving river overflows its banks. So stay three days in the delta watching the bore. The third day brings the full moon of October and the bore should be at its maximum strength until next fall. With apprehension, feel the strong north wind which is blowing. If it holds, it will flatten the bore.

On the last day, pack your supplies in the boat. Be ready to leave just after the last surge of the of the bore has passed. The time of the flood tide will be barely enough time for you to reach the ferry. Had it taken more than the three and one-half hours of the flood tide for you to find appropriate high ground for the camp, the return trip would have needed two stages of the flood tide, and the intervening hours of the ebb, spent up one of the many sloughs-confined to the small boat by the knee-deep mud and at the complete mercy of the vicious mosquitoes would be an experience you would be glad to bypass.

In the last hour at your camp, check the numbered feet from the bluff's edge and find four feet gone. Wonder where that eroded earth will be distributed-sand bar? mud bank? the depths of the gulf? Look for the last time at the heavily saturated soil of the delta and wonder where the water which lies on the land with immense weight will go -to thunder clouds? to the gulf? deep into the earth of delta barrier?

For the last time you see the bore bring the flood and race up-river to lose its strength more than forty miles above the place of its beginning. You see it held down by the strong north wind. Until next fall, the bore will be little more than a rapid rise of tide, for the normal tides of the gulf do not generate the power of the equinoctial bores.

So start back to the ferry after the last surge has passed and on the way see two whooping cranes, their long necks stretched in flight, the black feathers of their under wings etched sharply against the sky-and curse that the camera is packed and that they are gone before you get a photograph.

At the ferry, be surprised that you are welcomed with such warmth until it is discovered that they thought you lost! Who can stand in the path of "the big one" and not know disaster? Then-when it is all over-then realize hazard escaped and advantageous fortune. So, report to the Mexicali police and clear the record.

Find also that your car, threatened by the flood water (it would have been over the wheels in mud), was protected by a dike which the Mexicans built around it. See the handprints in the mud where it was packed into place. Have your money for their work refused. Have your muchas gracias accepted.

Leave the delta, sunburned, bearded, wiser. You have seen the bore that was first written about by a white man, Ulloa, in 1539 when he "... perceived the sea to run with so great a rage into the land that it was a thing much to be marvelled at. ." during the voyage which discovered that Baja California was a peninsula and not an island.

Three years later Hernando de Alarcon discovered the mouth of the Colorado River but only after he, too, had experienced the bore. Almost immediately after his arrival at the head of the gulf, his three ships were driven on sand bars "in such sort that one could not help another, neither could the boats succour us because the current was so great . . . Whereupon we were in such jeopardy that the deck of the Admiral was oftentimes under water; and if a great surge of the sea had not come and driven our ship right up and gave her leave, as it were, to breathe awhile, we had there been drowned."

In November of 1922, one of the greatest tragedies in the history of the Colorado occurred near La Bomba as a direct result of the tidal bore. The 36-ton steamer, The Topolobampo, left Guaymas with 125 persons and their families, headed for the cotton fields of Mexicali. As the tiny, overloaded steamer crept up the river, a small tide started rising, so it anchored near La Bomba for the night. Steel hausers anchored the ship securely to the sand bars, and under bright moonlight, passengers and crew went to sleep.

Near midnight, they were awakened by a great roaring like that of a tremendous waterfall rushing toward them. Before they could do more than see a wall of water fifteen feet high speeding toward them, the steamer was struck squarely abeam, the hausers snapped and the boat rolled over like a log.

Only thirty-nine passengers survived. Days later, when they were dragged from the mud flats, they were half insane from thirst, raw from the bites of swarming, predatory insects, starved, and blistered from sunburn.

Such great bores as this were a rarity even before the discharge of the Colorado River became controlled by its dams and the opposing force of the river-versus the ability of the flood tide of the gulf to come over it was lessened and the bore was tamed.

But when heavy northern snowfalls dictate heavier discharge of the river water from the dams, and the river is full at the time of the equinoctial tides, the bore runs with its old fury, and the delta is flooded. The surging weight of the bore not only holds back the river water, it also givesadditional impetus, by its sudden, massed onslaught, to the spread of the flood.

The renewing silt which once came down the Colorado River and added one cubic mile each hundred years to the barrier which holds the Gulf out of the Salton Sink in Southern California, is now being impounded behind the upper dams. The barrier is no longer the aggressor against the gulf tides or against the river floods, and the land is left vulnerable.

Because its soil is fine-grained, tightly packed, the land does not accept the flood water quickly. There is little porous space through which the water can seep. But the delta is not rock. It is earth already once transplanted by water.

The is earth so flat that the rising tide flows miles distant from the channel of the river. It is earth that looks dry, yet fills a footprint with slow water. It is earth soft with hidden water.

The equinoctial bores and the river which cannot be contained in its channel bring the evident flood to the delta. Latent flood percolates with infinite slowness through the delta barrier toward the point of final saturation and toward the areas of lowest level when the delta is under flood.

Who can measure the ground waters of the delta? Who can say that a part of the water inching daily higher in the Salton Sea did not once rest on the delta?

THE COLORADO DELTA, Godfrey Sykes, Carnegie Institution of Washington and the American Geographical Society of New York, 1937.

"The Seven Cities of Cibola," C. P. Vetter, THE RECLAMATION ERA, October and November, 1949.

"California's Weird Overflowing Sea," Keith Monroe, THE SATURDAY EVENING POST, August 30, 1952.

THE COLORADO, Frank Waters, Rinehart & Co., New York, 1946.

GROUND WATERS OF THE INDIO REGION, CALIFORNIA, With a Sketch of the Colorado Desert, Walter C. Menden-hall, Water Supply Paper 225, Document No. 1296, Government Printing Office, Washington, 1909.