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TABLE XIV.- Estimated direct and indirect damage caused by recent floods in major damage areas 1 of the Pajaro River Basin

Palaro River from mouth

to San Benito River.

Chittenden gage.

do

Do.

Cubic feet
per sec-

ond
Feb.19374 12, 500

{$63, 900 $9,000 $4,300

(2, 800) (800) (2, 300) Feb. 1938

169, 600 16, 200

53, 700 57, 800

|(25, 700) (6, 700) (24, 000) Feb. 19404

9, 900 1,500 0

0 (0) (0) (0)

$82, 500

$7,600 $69,500

$5, 600

$2,000 $200

(0) (1, 700)
16, 700 19, 600
(5, 500)| (31, 300)
0

700
(0) (0)

$0

(0) 11, 000

$0

(0)
21, 700

(0)

0 (0)

$1,700

(0)
3,600

(0)

0 (0)

$1,400

(0)
10, 100

(0)
3, 800

(0)

363, 800

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92, 200 212, 900

53, 100

do

0 (0)

6,000

0

4,500

Do.
Pajaro River above

mouth of San Benito
River--includes lower
Llagas Creek and San
Felipe Lake areas.

Do.

0

[blocks in formation]

0 (1,400)

6, 700

(0)

0 (0)

0 (0)

45, 200

30, 400

45, 200

30, 400

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do.

Feb. 1940

5, 700

Uvas-Carnadero Creek.

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11, 600

100

Dec. 1937 5

0

(0)
5, 200
(300)

8,000

0

(0)
6, 900
(5, 000)

0
(0)

100 11, 600 11, 100 120, 100

do.

$149, 100

(0)

0

(0) 1, 200

(0) 2, 000

(0)

Do. Llagas Creek above vi

cinity of mile 2.

Feb. 1940

7, 700

11, 600

0

0
(100) (0) (0)
104, 200 12, 700 18, 900

(1,700) (2, 100) (2,000)
13, 800

0

0
(600)
45, 700

0
(7, 400)

(0)

(0)
2, 300
(neg.)

(0)

(0)

5, 700

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do.

15, 800

600

15, 800

600

Dec. 1937

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8,600

Do...

(0)

0 (0)

do.

45, 700

7, 400

45, 700

7, 400

Feb. 1940

5, 700

(0) 0 (0)

(0)

[blocks in formation]

(0)

Inches

(0)

San Benito River below

Sulphur Canyon, mile

Type of damage-direct and indirect :

Damage-discharge or dam

Age-run-off correlation

point

Total damage Total damage for adjusted to floods indicated present channel

conditions

Damage area

Flood
date

Dis-
charge or

run-off

Agri- Resi-
cultural dential

Retail

Manu

Highfacturing, ways, process- / streets,

and
wholesale bridges

Public Channel
Rail- build-

Public
works,

utili-
rosd : ings and levees,

ties
grounds

etc.

ing, and

Direct

Indirect Direct Indirect

23.

1. 89

(San Benito River near

Feb, 1938
Willow
Creek school.
do.

Feb. 1940

13, 800

(O)

0 (O)

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0 (0)

{ {{

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0. 57

2, 400

(0)

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} 23,000 } 2, 400

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0

2, 400

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1 Flood plains of the upper Pajaro River and its tributaries merge at various locations, and, therefore, the assignment of damage to a particular source is necessarily arbitrary.

? Indirect damage enclosed in parentheses directly below direct damage. 3 Does not include cost of emergency patrols during flood periods. • Damage in Watsonville, Pajaro, and Watsonville Junction areas is influenced by levee construction of 1939 and 1940. • Damage in Gilroy and areas west of Gilroy is influenced by levee construction of 1938. • No data. Nore.—Loss of wages included in agricultural and urban damagés (retail column)-indirect damage. Cost of rescue work included in residential damage—iudirect damage.

35. Average annual flood damage. The damages set forth in table sou XIV are found to bear definite relation to peak discharge and volume ett of run-off as indicated in the table. The damage-discharge relativa ships were used in conjunction with the frequencies of peak discharged at the Chittenden and Uvas Creek gages to determine the frequein alie of varying amounts of flood damages to be expected in the flooded dat areas of the Pajaro and upper South Santa Clara Valleys, respectives

, per within a 50-year period which corresponds to the usual economic the of flood-control works. The damage-run-off relationship was usd in conjunction with the frequencies of various run-off depths at the Willow Creek School gaging station to determine the frequency of food damages of varying amounts to be expected in the San BenitoTres Pinos areas within a 50-year period. Division of the total estimated damages for the entire period by 50 gives the avera annual damage for each flood-damage area. These average annual damages are based on estimates of damage from recent floods, using normal pre-war commodity prices and are adjusted by giving conside ation to existing channel conditions and economic development in the flood plain. They are presented in table XV, separated into direct and indirect damages. This method of analysis is fully er-M plained in appendix IV,' and the derivations of the peak discharffrequency and the run-off-frequency curves are presented in appendir III.

TABLE XV.-Estimated average annual flood damages

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* Estimates include potential damage to urban Watsonville.

1 All these benefits are within the area described as Pajaro River above mouth of San Benito Rire. De cluding lower Llagas Creek and San Felipe Lake.

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36. Average annual damage from future floods.--Agricultural land in pouda the flood plain of the Pajaro River Basin has already reached is optimum development. Urban properties subject to flooding marke expected to increase somewhat in development in future years. However, the over-all damage from future floods is not expected to increa appreciably over that which would be experienced under present conditions from floods of the same magnitude.

37. Effect of floods on property values.- Land values in the field plain are not permanently depressed by, and, in some localities

, do not reflect at all, the flood hazard. If complete protection fine agricultural lands in the lower Llagas and San Felipe Lake flood place 'Ne prin floods were provided, however, it is estimated that some 900 acres of

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would be put to higher use with increased productivity and would increase in value about $140,000.

38. Intangible flood damages. The danger to life and health from floods in the basin is not great. Considerable mental distress is suffered in some localities because of the danger to property, and some reduction in school attendance because of flood conditions has been reported. Some intangible damage also is caused by the general disruption of communications during the large floods.

EXISTING FLOOD-CONTROL AND WATER-CONSERVATION WORKS

39. Flood-control works.-Levees have been constructed by local public agencies and the Work Projects Administration on Carnadero Creek, near Gilroy, and on both banks of the Pajaro River at and near Watsonville. With some relatively small additions, and with the rebuilding of some weak construction, found during this survey, these levees would be adequate, provided they are properly maintained. A number of private bank protection works have been constructed by individual property interests. Most of these are inadequate. The capital cost of the several public projects is summarized in table XVI.

TABLE XVI.--Summary of project costs for existing public lorees

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40. Reclamation and irrigation works.-- There are two legally constituted drainage districts in the watershed, No. 2049 and No. 2050,

both in Santa Cruz County. Together they cover 715 acres of land. The Hollister irrigation district, the Pacheco Pass water district, and the South Santa Clara water conservation district operate a number of small reservoirs and a canal system which serve the agricultural areas of San Benito County and the southern portion of South Santa Clara Valley. However, in a normal year, these developments are inadequate to meet the irrigation needs after the month of March. Appendix II ' contains more detailed information concerning these works.

IMPROVEMENTS DESIRED 41. Public hearing.- A public hearing for the preliminary examination of the Pajaro River for flood control was held in Watsonville January 5, 1938, by the district engineer jointly with local representatives of the Department of Agriculture. `About 60 persons attended, including representatives of Santa Cruz, San Benito, and Monterey Counties, the cities of Watsonville and Hollister, Pacheco Pass water district, Hollister irrigation district, local chambers of commerce,

H

* Not printed.

orchardists, and owners of business interests and property in the drainage basin. Excerpts from the transcript of the hearing, covering the more important testimony brought out at the hearing, arest forth herein. Presentation of the desires of local interests was spic

il sored by the chamber of commerce of Pajaro Valley and a committe of the supervisors of the four counties in which the drainage basu: lies: namely, Santa Cruz, Santa Clara, Monterey, and San Benito. ! No subsequent hearing has been held and no additional matters hare come to the attention of the district engineer which would indicate any modification in the desires of local interests as presented at the pu hearing on January 5, 1938. However, several levee improvemests any have been constructed on the river subsequent to the hearing with the laz assistance of the United States Work Projects Administration. Tront such projects now give considerable protection to Watsonville, Pajadas and Watsonville Junction, which have greatly reduced the urgenes and a of the need for protection in Pajaro Valley.

42. Improvements desired by local interests. The desires of lovalo interests vary according to their location. Some of these interets 5. are opposed to others. No concrete plan alone or in combination or with other objectives for flood control has been developed and agreed the upon by all local interests. Water conservation, especially for ratsa irrigation, and drainage problems are inseparably associated with him flood problems throughout the watershed. The essentiel desires of local interests, as expressed at the hearing and presented in various licu exhibits there submitted, are summarized as follows:

(a) South Santa Clara and San Benito Valleys.-(1) Prevention of overflow from Carnadero, Llagas, and Tres Pinos Creeks and varias minor tributaries and prevention of bank erosion in the San Berto River and Tres Pinos Creek channels, all by means of reservoirs sad sam spreading works where possible.

(2) Replenishment of underground water supplies, especially in the Gilroy and Hollister areas.

(3) Improvement of drainage in the bottom lands in the San Felpe Lake-Gilroy-Sargent area.

(6) Pajaro Valley.-(1) Prevention of overflow from the Pajero River and Corralitos Creek, continuing the natural regulation Dir effected by the lake area between San Felipe Lake and Sargent.

(2) Improved drainage and lowering of ground-water levels near Monterey Bay.

(3) Maintenance of an open river mouth into Monterey Bay.

43. The following specific projects were advocated as an immediate program necessary to partial achievement of the desired results

. The cost of this immediate program was estimated by local interests at $718,000, of which they proposed to contribute $ 155,000:

(a) Immediate program recommended by local interests.-- (1) Charmel clearing in the Pajaro River.

(2) Construction of spreading dams in the San Benito River and Tres Pinos Creek and at other locations in the Hollister irrigatilliset district.

(3) Construction of a reservoir on San Benito River near river mule 40, having a capacity of 6,000 acre-feet.

"(4) Construction of a reservoir on Tres Pinos Creek near river vile 20, having a capacity of 5,000 acre-feet.

(5) Enlargement and extension of existing levees, construction of

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