摘要:

In the absence of the author in Mexico City, an abstract was presented by J. B. Paulson, Jr.[It is understood that Dr. Bjerknes intends to publish the complete manuscript later in bulletin form.]

ISSN:0002-8606    

DOI:10.1029/TR022i001p00104

年代:1941

数据来源: WILEY

摘要:

The planning and design of flood‐control works on the tributaries and main stem of the Sacramento River inevitably requires the careful estimation and study not only of the floods of record and history but also of potential floods at various points in the river‐system. Such a study is now under way and this paper will describe some of the steps in that study that are of general interest.The Sacramento and San Joaquin rivers drain the Great Valley of California and the mountain slopes that surround it. This Valley lies generally north and south between the continuous barrier of the Sierra Nevada and the Pacific Ocean, being separated from the ocean, however, by the comparatively low coast ranges. The prevailing winds are from the west, with marine air flowing eastward over the coast ranges and the Valley and against the great barrier of the Sierra Nevada. During the summer dry season this air is extremely stable and practically no precipitation occurs. During the wet winter season, unstable storms pass across the area causing snowfall on the high slopes of the Sierra Nevada and heavy rainfall over the coast ranges, the valley‐floor, and lower slopes of the Sierra Nevada. The snow in the high country accumulates during the winter into a snow‐pack as much as 30 feet in depth. When this snow‐pack melts in the summer, it produces prolonged snow‐melt floods of moderate height but large volume on all rivers draining the high country. The wide‐spread storm‐rains cause short sharp floods on rivers draining the lower mountain slopes below the snow‐line. Occasionally, the storm‐air is so warm that there is rain instead of snow as high as the 10,000‐foot level and major floods may result on the rivers whose drainage‐areas extend up into the high country. The annual precipitation during the wet season increases from 10 to 15 inches in the Valley to 55 to 60 inches at the 5,000‐foot level on the Sierra slopes. Above this level, the annual precipitation slowly decreases to 40 inches at the crest of the Range. There is also a 50‐inch zone of precipitation along the seaward face of the coast ranges but this is quite narrow and the landward slopes, draining into the Great Valley, receive little more rai

ISSN:0002-8606    

DOI:10.1029/TR022i001p00106

年代:1941

数据来源: WILEY

摘要:

The winter storms which invade northern California originate through the interaction of Polar Pacific Air with Tropical Pacific Air. This happens when the polar low‐pressure areas are forced farther south than usual or the semi‐permanent high‐pressure areas just north of the Hawaiian Islands break down. Waves induced along this polar front or discontinuity‐surface between these two areas travel eastward across California. The passage of a family of as many as five such waves or storms has been noted. The development of the frontal system associated with these storms or low‐pressure areas is accompanied by heavy precipitation from the moisture‐laden Tropical

ISSN:0002-8606    

DOI:10.1029/TR022i001p00111

年代:1941

数据来源: WILEY

摘要:

The flood‐problem in the Sacramento River System is one in which the people of the Central Valley of California are vitally interested. A large proportion of the agricultural land of the Valley is reclaimed swamp and overflow‐land. Although many millions of dollars have been spent on reclamation and flood‐control, recent floods have indicated the need for further study. In order to determine the adequacy of the present system of levees and by‐passes, and to plan intelligently on future improvements, it is necessary to know the behavior of past and future floods. Therefore, a restudy of past floods has been made by routing these floods through the present system and possible modifications thereof. The results of these routings will furnish an excellent guide in predicting the probable future frequency of flows of any magnitude in any part of the

ISSN:0002-8606    

DOI:10.1029/TR022i001p00118

年代:1941

数据来源: WILEY

摘要:

Engineers and hydrologists engaged on flood‐problems throughout much of the United States east of the Rocky Mountains must deal to a considerable extent with wide‐spread storms covering thousands of square miles. The gradations of meteorologic conditions as regard both area and time are relatively homogeneous during such storm‐events and are affected but moderately by orographical influences. Under such conditions similar storm‐characteristics prevail over vast areas. True, precipitation decreases toward the boundaries of such major storm‐areas, and locally precipitation‐rates may greatly exceed the average. Often, however, drainage‐basin after drainage‐basin will yield comparable depths of flood‐runoff. The storms of March, 1936, which resulted in the simultaneous occurrence of floods throughout all of the northeastern part of the United States from Ohio and Virginia to Maine and the storm of January, 1937, which embraced all of the 200,000 square miles comprising the Ohio River drainage are typical of major Eastern disturbances. The storm of December, 1937, in the Sacramento and San Joaquin valleys is used herein to illustrate what may be called a typical major California disturbance, and it is this storm and resulting flood that I wish to consider in some detail and also to make such comparisons and contrasts with Eastern floods as seem to be of

ISSN:0002-8606    

DOI:10.1029/TR022i001p00124

年代:1941

数据来源: WILEY

摘要:

The Meeting was held in the Little Theatre of the Memorial Auditorium at Sacramento. This was furnished by the Sacramento Convention Bureau, which also furnished badges in which names could be inserted and a clerk to help with registration. Fred Sprague of the Pacific Gas and Electric Company furnished a lantern and showed the slides which the various authors of papers had prepared.Leupold, Volpel and Company through the good offices of J. C. Stevens exhibited one of the Stevens snow‐measuring apparatus and two types of Stevens water‐stage recorders. Considerable trouble and expense was incurred in doing this as Robert Stevens brought them down by truck from Portland and was available at all times for explanation. Otto H. Meyer, who also delivered a paper on the morning of January 17, exhibited a “flood‐routing” apparatus of his own design and construction. By this device with the hydrograph of a flood an any tributary, the hydro graph of the same flood at some lower point is readily a

ISSN:0002-8606    

DOI:10.1029/TR022i001p00129

年代:1941

数据来源: WILEY

摘要:

Mr. Chairman, and fellow members of the Western Interstate Snow‐Survey Conference: It is a source of great pleasure to all of us Sacramento snow‐surveyors that this year's meeting is being held in Sacramento. This city itself has always been more or less snow conscious because of the American River Watershed in our own backyard and the recurring high water in the rivers at our doorstep.The State Engineer's office here cooperated with Dr. Church on his early work as far back as 1917. Our present program extends back ten years, beginning in 1929 when under my direction, Harlowe Stafford, assisted by Spencer Munson, laid out a network of snow‐courses embracing the Sierra. Fred Paget has been looking after the details for the past five years, taking up where Harlowe lef

ISSN:0002-8606    

DOI:10.1029/TR022i001p00135-3

年代:1941

数据来源: WILEY

摘要:

Of the 1940 California forecasts, on the whole they were fair. For the 11 watersheds covered by the published forecasts, five of them were good with a difference between forecast and actual of from three to ten per cent; four of them were fair with differences of between ten and 20 per cent, while two were poor with discrepancies over 20 per cent.For some reason the 1939–40 winter weather did not at all conform to normal behavior. The cyclonic storms that bring California's winter precipitation forsook, their usual chilly path from the Aleutian Islands across the Gulf of Alaska to the mainland and instead followed a warmer route southerly to the Hawaiian Islands and then swung inland from there. These warmer storms from the tropical seas brought rain to elevations that usually receive only snow during the winter month

ISSN:0002-8606    

DOI:10.1029/TR022i001p00138

年代:1941

数据来源: WILEY

摘要:

The Edison Company's Big Creek hydroelectric development is served by three storage‐reservoirs, namely, Huntington, Florence, and Shaver lakes, having a combined capacity of 288,523 acre‐feet. These three reservoirs impound the runoff of Bear Creek, Mono Creek, South Fork San Joaquin River, Big Creek, Pitman Creek, and Stevenson Creek. The combined area of the six drainage‐basins is 450 square miles, 45 per cent of which is above an elevation of 10,000 feet.Forecasts based on snow‐survey data are made at monthly intervals beginning March 1, and, when heavy storms or operating requirements make it desirable, semi‐monthly forecasts are made. In general, all forecasts are based primarily on the results of snow‐surveys made at two key courses, namely, Huntington Lake, elevation 7,000 feet, and Kaiser Pass, elevation 9,200 feet. However, consideration is given to data from 17 other snow‐courses in the San Joaquin River Easin. when sufficient data have been collected from some additional courses recently established by the Company, all data from the several available sources will be correlated and new cu

ISSN:0002-8606    

DOI:10.1029/TR022i001p00139-2

年代:1941

数据来源: WILEY

摘要:

The runoff for the period April to July, inclusive, in the Mokelumne River as the result of melting snow at the high altitudes showed a large deviation between the measured runoff and the estimate prepared as the result of snow‐surveys taken on April 1.The preparation of the estimate of the runoff from melting snow during the past season was complicated by the fact that a very heavy storm occurred during the last three days of March, subsequent to the measurement of many of the snow‐courses. Furthermore, the fact that there was no snow on the ground below the 6,000‐foot elevation possibly affected the subsequent runoff, due to the smaller area covered by the snow‐field and the consequent lower evaporation‐ and transpirati

ISSN:0002-8606    

DOI:10.1029/TR022i001p00140

年代:1941

数据来源: WILEY