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Lake inlet channel continues northwesterly through channels toward Tulare Lake. When the total run-off exceeds about 1,100,000 acrefeet, flow begins to enter the reclaimed area in Tulare Lake Basin, and other lands in the trough of the valley. This condition of unregulated flow is seriously aggravated if storage capacity in Buena Vista and Tulare Lake Basins is reduced by carry-over of flood waters from the preceding year, and when Kings, Kaweah, or Tule Rivers also discharge into the Tulare Lake area. Table 18 lists the years in which the seasonal run-off of Kern River exceeded 1,000,000 acre-feet.

TABLE 18.--Seasonal run-off exceeding 1,000,000 acre-feet, Kern River

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1 1871 to 1893 from estimates in Bulletin No. 5, Flow in California Streams, California Department of Public Works, 1923. 1893 to 1938 from stream-flow records at first point of measurement. 2 Estimated. à Greatest flood of record.

49. Reasonably accurate estimates of seasonal run-off of Kern River have been made for the period 1872 to 1893, and actual run-off records are available for the period 1893 to 1938. These were used to estimate the probable future occurrence of late spring floods. The frequency curve from which data in table 19 were derived is included in appendix V.

Table 19.-Estimated frequency of seasonal run-off and probable mean daily flows, Run-off from this watershed is very rapid and has given rise to comparatively high flood peaks in the mountains. The most severe flood known on the stream occurred in September 1932 as a result of a cloudburst on Tehachapi Creek, one of the main tributaries. Flows esti

Kern River at first point of measurement

Number of
occurence in

Total seasonal
run-off, acre-

Maximum
mean daily

flow, cubic
feet per second,
equalled or
exceeded :

100 years

feet!

1

1
2
3
4
5
6

2, 540,000
2, 200.000
2,000,000
1,850,000
1, 730,000
1, 640,000
1, 490,000
1,370,000
1,030.000

910,000

10,000
9, 600
9,000
8, 600
8, 100
7,800
7, 300
6, 900
5,500
4,900

20
25

1 Figures shown are independent and would not necessarily occur in the same year.

50. Poso Creek and Caliente Creek floods.--The relatively infrequent floods on Poso Creek are caused by heavy rainfall. Flash floods with relatively low peaks occur on this creek, Floods on Caliente Creek are also of infrequent occurrence and are caused by intense rainfall.

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. mated from high-water marks in the canyon reached a peak of 40,00 cubic feet per second, but were greatly reduced by channel storage and natural spreading before reaching the valley floor. The California State Division of Water Resources, in a report dated January 1933 estimated the frequency of this flood at about once in 90 years

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VIII, FLOOD DAMAGE

51. Kern River, general.- There have been 10 damaging floods on Kern River during the past 45 years. Five were of the winter and five of the late spring type. Although accurate records of damage caused by prior floods are not available, those of 1937 and 1938 provide evidence of the possible damage to be expected from floods on Kern River, and data have been compiled to show the extent and damage of these floods. Since February 1937 there have been two floods of each of the two types. The data obtained by field surveys and questionnaires form the basis for the flood damage estimates given in detail in appendix VI.

52. Damage from winter floods, Kern River.-Winter floods cause extensive damage to levees and irrigation structures along the river channels. Consequent failure of levees has resulted in property damage in oil fields and suburban areas in the vicinity of Bakersfield. The city itself has been threatened many times, but has been protected at considerable expense by patrolling and emergency maintenance work during floods. In February 1937 inundation of Bakersfield was narrowly averted when an additional rise of less than 1 foot would have overtopped the levees protecting the city. The inundation of Bakersfield would have resulted in a loss estimated at $5,500,000. Agricultural losses occurred principally in the Goose Lake Slough area. Damages caused by the 1937 and 1938 winter floods are given in table 20.

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53. Damage from late spring floods, Kern River. --Flows of late spring floods generally pass through the channels of the upper

delta region without damage. However, overbank discharge similar to

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that of winter floods occurs along the smaller channels of the lower river, with resulting damage to crops, roads, levees, irrigation structures, and miscellaneous property. More serious damage results from flooding of the reclaimed basins of Buena Vista Lake and Tulare Lake. Such inundation not only destroys the crops already growing, but makes it impossible to farm the lake areas for one or more seasons thereafter. As an example, the late spring floods of 1937 and 1938 completely filled the Buena Vista Lake reservoir, and at least 15,000 acres which might otherwise have been farmed will be out of production for several years. Similarly, there will be approximately 100,000 acres in Tulare Lake basin out of production for 2 years or more. These late spring floods also inundated and caused agricultural damage on about 110,000 acres of land upstream from Tulare Lake along the various channels. In addition extensive repairs to levees and structures in the lake basins were required after each flooding. Damages from the late spring floods of 1937 and 1938 are tabulated in table 21. In these years, total damage in Tulare Lake basin resulted from simultaneous inflow from the Kings, Kern, Kaweah, and Tule Rivers. The total damage in the lake basin was $2,613,000 in 1937, and $8,920,000 in 1938. A special study was made of Tulare Lake flooding in order to determine the proper allocation of damage to each of the four contributing streams. Because of the progressive inundation of cells or reclamation units as the volume increases, damage in the lake basin is roughly proportional to the total volume of water in the lake. This relation is illustrated on plate D of appendix VII. Total damages from the 1937 and 1938 floods were divided among the four rivers on the basis of the proportion of the total inflow contributed. Inflow from Kern River was 23.5 percent of the total in 1937 and 18.9 percent in 1938. The corresponding damages charged to Kern River are given in table 21.

TABLE 21.--Flood damage, late spring floods, Kern River, 1937-38

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54. Summary of 1937 and 1938 flood damages, Kern River. --Damages resulting from the four recent Kern River floods are summarized in table 22.

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1, 251, 600

2,035, 200

55. Average annual flood damage, Kern River.--Flood-loss data for 1937 and 1938 were used as a basis for estimating the probable average annual damage from future Kern River floods. These data, as compiled from field surveys, were not considered representative of average conditions because of the short period between floods. Inspection of past records shows that flood years are generally separated by several years of normal or subnormal run-off and that the probability of recurrence of 2 successive flood years, such as 1937 and 1938, is relatively remote. Large areas, including Buena Vista and Tulare Lake basins, which were flooded in 1937, were not planted in 1938. If the 1937 flood had not occurred there would have been greater acreages planted in 1938 and the damage from floods of that year would have been considerably greater than were shown from actual surveys. Therefore, in order to determine the effect of future floods of similar magnitude, known damage from the 1937 flood was used in computing the damage caused by floods not influenced by previous flooding. The method used in each area was essentially the same, but was varied in detail to fit local conditions. The determination of average annual flood damage is described in appendix VII' and the results are summarized in table 23.

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56. Indirect and intangible damage.--In addition to the direct damages indicated in paragraphs 52 to 54, there are numerous indirect damages which result from floods. The most important of these are:

(a) Menace to lives and social security of residents.

(b) Unhealthy conditions and spread of disease resulting from polluted water supply. During the recent floods, a number of domestic wells were poluted. The wells of the Western Water Co., which supply the municipality of Talt

, were also in danger of contamination.

(c) Danger, expense, and inconvenience to travelers on highways and railroads traversing the area.

(d) The cost of moving from and returning to flooded areas as well as the extra cost of maintaining a temporary residence.

(e) The disruption of business and community life during and after floods. ! Not printed.

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57. Flood damage, Poso Creek.--The 1937 flood on Poso Creek caused losses estimated at $50,000, most of which were due to damage to roads and bridges in the watershed and on the valley floor. Damage to the scattered agricultural developments along the stream was small and probably was less than the value of the additional water added to the ground-water supply. Due to the lack of data on which to base a flood-frequency study, no estimate was made of average annual damage from Poso Creek floods.

58. Flood damage, Caliente Creek.-The most disastrous flood on

Caliente Creek occurred in September 1932 as a result of a cloudburst et too on the upper watershed. This flood caused the death of at least 15 Der persons and property damage estimated at $700,000. Many buildings cond tiny were swept away and damage to roadway and bridges of the State sa highway was extensive. Several miles of railroad and 9 bridges de of the Southern Pacific Co. were washed out. Some of this construction Te had seriously obstructed the creek channels. The damage was almost hot entirely confined to the area within the canyon; damage on the valley

floor being only of minor nature. The railroad has since been relocated anh on higher ground and is not now subject to serious damage. Two eben recent floods, occurring in 1937, resulted in excess flows from this creek

spreading over a limited area on the valley floor. Losses from these 2 floods consisted of minor damage to roads and a small amount of erosion of agricultural lands; the total approximating $10,000. Because of the infrequency of such flood flows and the improbability of recurrence of the cloudburst” type of flood, no estimate was made of average annual flood damage on this creek.

IX. SURVEY

59. Kern River.-In the formulation of this report, surveys were necessary to obtain data on hydrology, flood damage, irrigation practices, power development, and other pertinent matters. Studies of flood characteristics indicated that an adequate plan for flood control would require detention storage on the main river. Therefore, aerotopographic, geological, and subsurface surveys were made of various possible dam and reservoir sites, and the Isabella site was selected as the most practicable. Field and office studies were made of hydrology, flood damage, power development, and irrigation. These studies are described in detail in various appendixes and the results are discussed in appropriate paragraphs of this report. In connection with the survey the district engineer inspected the area and the sites of proposed improvements from time to time.

60. Survey-Poso and Caliente Creeks. The survey investigations for Poso and Caliente Creeks included a search for reservoir sites, inspection of channels, and collection and compilation of pertinent data. The studies included consideration of flood run-off, flood damage, underground water, irrigation, and water rights. As no suitable reservoir sites were found, spreading of surplus flows near the foothills was determined to be the most feasible solution for flood control on both creeks. Poso Creek now constitutes an important source of water supply in its lower reaches, and upstream spreading would interfere with such use.

The initial and maintenance costs of adequate spreading works would be high. Considering the infrequent and minor nature of floods on Poso Creek, a project would not be economically

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