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The statistics presented at the bottom of page 16 and the top of page 17 of this brief were assembled in the early part of 1945. Since then, there has been a tremendous increase in assessed valuation within the area subject to flood hazard, partly because of the vast expansion due to the war years and partly because of raises in assessed valuations amounting in some cases to as much as 450 percent.
A new study made early in March 1947, discloses that there is imperative need of protection from floods originating at or above the Whittier Yarrows for the following population and property located in Los Angeles and Orange Counties: 50,000 acres of highly developed land, 60,000 homes, 200,000 population.
An assessed valuation in excess of $150,000,000.
Many plants of strategic importance to the national defense owned or financed by the United States Government at a cost of $130,000,000 to $140,000,000, and not included in the assessed valuation of $1.50,000,000 above mentioned, are located within this area subject to flood hazard.
Among these plants are the following:
3. The Long Beach Municipal Airport, headquarters during the war for the Farrying Command of the United States Air Corps.
4. The United States naval air station at Los Alamitos.
The actual market value of all the property subject to such flood hazard exceeds half a billion dollars.
BRIEF ON BEHALF OF THE BOARD OF WATER COMMISSIONERS OF THE CITY OF Long
Beach, TO BE PRESENTED TO THE UNITED STATES DISTRICT ENGINEER AT Los ANGELES AT A PUBLIC HEARING CALLED FOR DECEMBER 12, 1946, Ox A RESTUDY OF THE WHITTIER NARROWS PROJECT AND ALTERNATIVE PLANS THEREFOR, Ix Los ANGELES COUNTY, CALIF.
(By Walter M. Brown, office engineer, Long Beach water department)
This brief is presented pursuant to a motion adopted by the Board of Water Commissioners of the City of Long Beach at a regular meeting held by it on Thursday, December 5, 1946, as follows:
"Commissioner O'Neil moved, seconded by Commissioner Wall, that the board of water commissioners authorize the preparation and presentation, on behalf of the board of water commissioners, at the hearing in regard to construction of the Whittier Narrows Dam to be held December 12 before the district engineer, United States Engineer Department, of a brief supporting the construction of said Whittier Narrows Dam.
“Carried by the following vote: Ayes: Commissioners Johnson, O'Neil, Hilbert, and Wall. Noes: None. Absent: Commissioner Winstead."
Peculiarities of climate and topography of Los Angeles County and adjacent areas are responsible for the destructive and unpredictable floods which are characteristic of this region. These are well understood by the district engineer. United States Engineer Department, at Los Angeles, and his staff. They are. however, entirely outside the experience of the vast majority of the population of the United States, particularly in the East and South, where the fate of most flood-control projects is decided. It therefore seems advisable to open this brief with a discussion of the peculiarities which serve to make this area unique.
DRAINAGE AREAS AND STORM SEASON
The drainage areas of the San Gabriel River and its tributaries are short. the valleys variable in slope but relatively flat, and the mountains exceedingly steep. The greatest length of the San Gabriel watershed, from the ocean front on the south to the highest mountain crests on the north, does not exceed 50 miles This distance takes one from sea level to elevations in excess of 7,000 and 8,000 feet.
The rise from sea level, in the first 20 miles, approximates 215 feet to the site of the proposed Whittier Narrows Dam as shown in plan A of the Ariny
engineers. The 1,000-foot contour marks the approximate base of the mountains, and is reached in another 11 miles. The rise from the 1,000-foot contour to the crest of the range occurs in a final 20 miles or less.
Thus we have gradients averaging.about 11 feet to the mile in the first 20 miles, 70 feet to the mile between the Whittier Narrows and the base of the mountains, and 300 to 350 feet to the mile in the mountains themselves, with some grades running as high as 2,000 feet per mile for a distance of approximately 2 miles.
The steep slopes of the San Gabriel Mountains generally hold only a thin layer of soil. They support a few forests and those of limited extent, usually in mountain meadows. In general, their vegetative cover is a growth of low brush and chaparral.
These mountains most effectively precipitate the moisture from the storm clouds blowing in from the ocean, practically wringing them dry, and leaving little moisture to pass on into the desert to the north. The storm season embraces the period between November 1 and the following April 15. The precipitation is mostly in the form of rain. Although snow sometimes falls in the higher mountain levels, it seldom lies on the ground for more than a few days at a time.
Normally, precipitation increases in intensity with distance from the ocean and proximity to the mountain crests. Rainfall at Long Beach during the last 25 years has averaged about 13 inches per annum. The Los Angeles average over a period of 69 years is 15.5 inches. The annual rainfall in the San Gabriel Mountains averages about 20 inches at their base and from 35 to 45 inches at their crests. The seasonal rainfall, however, has been known to exceed these averages by more than 230 percent, both in the city of Los Angeles and in the San Gabriel Mountains.
Under these conditions-a very short watershed with excessive mountain grades of low absorptive capacity which sluice the run-off onto the relatively flat valley or plain lying between the mountains and the sea, combined with violent and more or less unpredictable storms, which often approach cloudburst proportionstremendous floods may occur at any time during the storm season. They most often occur in one or two months of the following four, to wit: December, January, February, and March.
From April 15 to November 1 of each year we receive little or no rainfall. Our river channels are usually dry and dusty in summer and objects of derision to eastern tourists. But in winter they often carry tremendous and destructive floods,
Two distinct types of storms are prevalent in this region. The normal storm is of prolonged duration but of average intensity. The cloudburst type of storm is what its name implies, a storm usually of short duration but of intense precipitation. Either type of storm may break at any time during the storm season, either in the mountains or over the valley or both.
And the prolonged "normal" storm may also be accompanied by the cloudburst type in localized areas.
RECENT STORMS OF RECORD
A heary storm occurred February 18–21, 1914, in Los Angeles County and caused flood damage approximately equal to that occurring in the entire State of Kansas during the same year. As a result of the heavy property loss; caused by this storm, a board of engineers was appointed in April 1914 by the board of supervisors of Los Angeles County to prepare a comprehensive plan for flood control. This board submitted its report under date of July 27, 1915.
The board of engineers came to the conclusion that the flood of 1889 was probably the maximum flood of record and that the discharge from the San Gabriel River was approximately 47,000 cubic feet per second. On page 146 of the report, Mr. H. Hawgood, one of the board, states—"It is not conceivable that any flood of the Los Angeles or San Gabriel Rivers ever exceeded by 361/2 percent the flood of 1889."
This would have meant a storm flow of approximately 6-4,000 cubic feet per second. Mr. Hawgood's statement is particularly noteworthy in considering a storm which culminated March 1938, and which produced a peak flow of 95,000 cubic feet per second into San Gabriel No. 1 food-control reservoir about 3 miles below the forks of the San Gabriel River. Fortunately, this peak lasted only a few minutes, although an inflow of 80,000 cubic feet per second or more continued for slightly more than 2 hours, and an inflow of 60,000 cubic feet per second or more for more than 5 hours. Fortunately, also, two flood-control dams and one conservation dami had been constructed in the San Gabriel Canyon in the mean
The initial capacities of these dams and their capacities as determined folJowing the storm of March 2, 1938, were as follows:
Even the brief periods mentioned above were sufficient for the floodwaters to overtop the spillway crests of all three of the dams, notwithstanding the release of 25,000 cubic feet per second from the Morris Dam, which release was later increased to 35,000 cubic feet per second.
Records show that the crest of the flood, estimated at 99,000 cubic feet per second reached Long Beach at 9 p. m. on March 2. Just above the junction of the Los Angeles River and the Rio Hondo, the former carried a peak of 79,000 cubic feet per second and the latter a peak of 24,100 cubic feet per second. 7 p. m. of the same day, the writer of this brief watched the floodwaters licking the top of the rock revetment on the west side of the Los Angeles River floodcontrol channel just south of Anaheim Street, Long Beach. At that time the rails of a railroad track on the top of the revet ment afforded the only additional protection to a low-lying industrial area west of the flood-control channel, and to the Long Beach Harbor itself. A break-through would have caused untold damage.
The earth embankments of the San Gabriel River channel, lying above the surface of adjoining lands, were washed out east of Long Beach, and a large area of farm land inundated. It should be noted that most of the future expansion of Long Beach must be eastward, over this same inundated area.
If the mountain storm had maintained its intensity a short while longer, the entire peak flow of 80,000 to 95,000 cubic feet per second into San Gabriel Reservoir No. 1, augmented by the flow of many tributaries discharging abore the Whittier Narrows, would have come on down the valley, and the loss of life and property from Azusa to El Monte and from El Monte to Long Beach would have been nothing short of catastrophic.
On March 7, 1938, only 5 days after this flood, another storm of equal intensity was predicted for March 9. The district engineer of the United States Engineer Department at Los Angeles at that time stated at a public meeting held shortly thereafter that, inasmuch as all the San Gabriel reservoirs were full and the ground completely saturated, he made his preparations for a major disaster and “never so helpless in his life.” He further reported that only the interposition of an unexpected barometric “high.” which held the "low" out at sea until the major part of the storm was dissipated, saved this area from a disaster of the first magnitude.
Again, on January 21–23, 1943, another stormr occurred over Los Angeles County which produced the maximum 24-hour rainfall of record in southern California26 inches at Camp LeRoy and 22 inches at Camp Singer. The rainfall for the 56-hour storm was 4.97 inches at Long Beach, increasing to 37.34 inches at Camp LeRoy and 33.66 inches at Camp Singer.
However, the ground was dry when the storm began and much of the precipitation was absorbed. Although the run-off reached food proportions, the flood flows were considerably smaller than those of March 2, 1938. Notwithstanding this fact, the flow in the Los Angeles River flood-control channel, augmented by the Rio Hondo flow, overtopped the bank of the channel for a few minutes at one spot in Long Beach though with negligible damage.
An additional flood-retarding basin known as the Santa Fe has now been partly completed on the San Gabriel River debris cone, approximately halfway between the mouth of the San Gabriel Canyon and the Whittier Narrows. Opponents of the Whittier Narrows Dam have stated that the Santa Fe Dam, together with a recently executed contract between the metropolitan water district of southern California, the Los Angeles County flood-control district, and the San Gabriel Valley Protective Association, for joint use of the Morris Reservoir, will provide all the flood control that is necessary.
Nothing could be further from the truth. The three-party contract just referred to gives the flood-control district the right to use, for 15 years, half of the capacity of the Morris Reservoir, estimated not to exceed 17,500 acre-feet, for flood-control purposes during the storm season. There is no reason to suppose that this right will be renewed.
By the same contract, the San Gabriel Valley Protective Association is given the right to use 50 percent of the reservoir capacity for conservation purposes (subject to the flood-control district's right to use the same space for food-control purposes during the storm seasons), decreasing at the rate of 10 percent every 6 years. Thus, the flood-control district's rights in the Morris Reservoir terminate in 15 years, and those of the protective association in 30 years.
Furthermore, while the four existing dams, San Gabriel Nos. 1 and 2, Morris, and Santa Fe, regulate the run-off from 236 square miles of the San Gabriel watershed, or 43 percent of the area tributary to the Whittier Narrows, there is another tributary area of 316 square miles, or 57 percent, over which the four dams exercise no control whatever. This is the area of greatest flood hazard to Long Beach and other communities on the coastal plain, although it should not be overlooked, that the regulated discharge from the four dams above-mentioned must also pass through the Whittier Narrows and add to the flood hazard of the area below.
Again, the flood hazard is not static but is continually on the increase. Every bit of land which is put under an impervious covering, whether it be a new roof, a paved yard, or road, and every new storm drain discharging into the Rio Hondo or the San Gabriel River north of the Whittier Narrows, as well as every forest fire that denudes a portion of the watershed of its cover, adds to the flood hazard. Meanwhile, the capacity of existing dams is being reduced by silting during every major storm. A former chief engineer of the Los Angeles County food. control district stated that "after a normal watershed cover has been denuded, erosion rates will increase from 50 to 100 times that with undisturbed vegetation."
San Gabriel food-control dams Nos. 1 and 2 have lost more than 11,000 acre-feet from this cause, or about 17 percent of their total initial capacity, since they were constructed 9 to 11 years ago.
A series of small dams designed to retard the flood flows from nine small watersheds along the south slope of the San Gabriel Mountains tributary to the Whittier Narrows, which had an initial aggregate capacity of 6,717 acre-feet, have lost 30 percent of their combined capacity through silting.
So far, this brief has dealt with the subject of flood control, inasmuch as the Army engineers are charged with the construction of food-control works. However, the conservation of water is of secondary importance to food control in this region only because it begins with flood control. If there is no control of floods, there can be little conservation of flood flows.
The metropolitan area of southern California has been carved out of a desert. Without more water than nature provides it will revert to a desert. Only 1.4 percent of the waters of the State of California originate south of the Tehachapi Mountains, while more than 40 percent of the population of the State-perhaps as much as 45 percent—is located in this scantily watered region. Consequently, it is of the highest importance that every possible drop of floodwater be conserved and put to beneficial use.
Sature has provided this area with two great underground storage basins, ohe above and one below the Whittier Narrows. Anticlina] folds of the earth's crust form the lower lips of these basins and act as barriers to hold the underground waters back.
The upper San Gabriel Basin is like a tilted saucer or bowl, the lower edge of which is a partially eroded fold connecting the Puente Hills on the east and the Merced Hills on the west.
The lower basin is much flatter and is formed by another fold which passes through Dominguez and Signal Hills, Anaheim Landing, and other high points. Both basins contain great bodies of absorptive sands and gravels which store large quantities of water.
Both basins are supplied to some extent by direct rainfall, but chiefly by the run-off from the areas lying to the north of them. The capacity of the upper San Gabriel Basin to retain water is limited by its rather high tilt. Percolating waters are forced to the surface at the Whittier Narrows by the constriction which occurs at that point in both width and depth, and these rising waters become a portion of the supply of the lower or Coastal Plain Basin.
It is from this Coastal Plain Basin that the city of Long Beach derives most of its water supply. During each of the last two fiscal years, the city pumped nearly 23,000 acre-feet for municipal use, from 25 wells, widely scattered in the area north and east of Signal Hill.
Most of the replenishment of the underground water supply of the Coastal Plain occurs in the so-called forebay area, lying between Downey and the Whittier Narrows. Beginning in the neighborhood of Downey, clay beds appear, which become more numerous and thicker as the coast line is approached, and which materially interfere with percolation of surface water, and ultimately cut it off altogether. The fact that the area south of Downey was artesian for a long time. and that artesian flows still appear in portions of it during or following seasons of high precipitation is due to these clay beds, which form an effective artesian cap, preventing percolation upward or downward.
In 1895, a well widely known as the Big Bouton was drilled east of the Los Angeles Terminal Railroad, now a part of the Union Pacific system, and slightly north of the site of Carson Street. This well came in, according to authenticated records, with a pressure of 35 pounds per square inch. This is equal to the weight of a column of water so feet high.
The Big Bouton well flowed for the last times in the winters of 1915 and 1916. Since then, the static water level has steadily declined until, on August 19, 191-16, it reached a low of 115 feet below the ground surface, or nearly 19 feet below sea level-a drop in combined pressure and water levels of 195 feet in the last 51 years.
In the meantime, the 1946 pumping levels in some of the Long Beach wells show the following depths below sea level : Citizens Well No. 5, 81 feet in September; Alamitos Well No. 9, 94 feet in September ; Commission Well No. 1, nearly 94 feet in October. These wells are rather widely spaced.
It is this downward trend in water levels, which is taking place all over the Coastal Plain in varying degrees, that makes the city of Long Beach so insistent upon the need of water conservation in conjunction with flood control, especially as we are now nearing the end of an 11-year wet cycle and must look forward to the occurrence of a dry cycle in the near future-a (ycle of less than average precipitation.
We are also faced with a very definite threat of sea-water intrusion if this trend is not soon stopped. This is because the "barrier" which accompanies the Newport-Inglewood fault zone and which forms the southwesterly lip of the Coastal Plain Basin is not impervious.
Six or seven years ago the United States Geological Survey was brought in to make a study of this danger. Their work has disclosed that 9 miles out of 27 along the crest of the anticlinal fold forming the “barrier" have been eroded away to depths of as much as 150 feet below sea level. Subsequently, these gaps hare been filled by recent detrital material which is permeable and capable of passing water in either direction.
Therefore, the only means of protecting the fresh water supplies of the Coastal Plain from ocean water intrusion is to maintain a head of fresh water a few feet greater than the salt water head. In other words, the sea can be kept out only by maintaining a liquid dam of fresh water in these eroded areas.
Under such conditions, the depth to which water can be safely withdrawn from the ('oastal Plain is limited, and everything indicates that the water levels in the Long Beach wells are very close to that limit now. Only the fact that these wells lie a few miles back from the ocean have protected them this long, by permitting recovery of the water levels to sea level or above before reaching the barrier.
Consequently, anything that tends to increase the percolation of flood flows into the gravels of the Coastal Plain is of the utmost importance to the city of Long Beach. The engineering staff of the Long Beach Water Department has long realized that it does not dare take from the city wells enough water to supply the city's full requirements. If that were done, it would precipitate the rery thing we are trying to avoid-an invasion of sea water.
Long Beach is a member of the Metropolitan Water District of Southern California. It, therefore, has a second water supply available. As a matter of fact, Long Beach purchased nearly 5,000 acre-feet of Colorado River water in the fiscal year ending June 30, 1915, and almost 9,600 acre-feet in the year ending June 30, 1946, at costs approximating $75,000 and $144,000, respectively.
However, the local water supply, practically all of which comes from the underground waters of the San Gabriel and Rio Hondo, is far superior in quality and