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Chapter 4 -- Watershed Processes and Aquatic Ecosystems (continued)

Hydrology

The Smith River is a fifth order stream according to river reaches defined by the Environmental Protection Agency (EPA 1994). The North Fork, Middle Fork, and South Fork are fourth order streams. There are at least 325 first order streams in the watershed. Several gauging stations are (or were) located in the Smith River watershed (Tables 21 and 22).

 

Table 21. Stream gauging stations in the Smith River system (California Dept. of Water Resources 1970).

Station name:

Location description:

Smith River

0.5 miles downstream from South Fork and 8 miles east of Crescent City

North Fork Smith River

0.5 miles upstream from Middle Fork confluence

Middle Fork Smith River

0.6 miles upstream from North Fork confluence

South Fork Smith River

2 miles upstream from mouth

Rowdy Creek

0.6 miles south of the Smith River and 12.2 miles north of Crescent City

 

Table 22. Information about stream flow gauging stations in the Smith River watershed (Winston and Goodridge 1980, US Corps of Engineers 1971, California Department of Water Resources 1970, USGS 1997).

 

Smith River

North Fork

Middle Fork

South Fork

Mill Creek

Rowdy Creek

Period of record

1931 - 93

1911 - 13

1911 - 17,

1958 - 65

1911 - 16,

1954 - 61,

1977 - 79

1974 - 81

1957 - 62

Drainage (sq mi)

613.6

158

131

291

28.6

33.3

Elevation (feet)

79

350

353

150

250

25

Avg runoff (in/yr)

82.01

65.64

73.99

90.03

70.82

78.13

 

The Smith River watershed produces the highest runoff per area in California (Winston and Goodridge 1980). Average annual runoff for the entire basin is about 2.9 million acre feet. Like virtually all coastal rivers in the Pacific Northwest, the Smith River undergoes extreme variation in stream flow (Table 23). Stream flow is low during the summer and early fall and high during winter and spring. During the summer, base flows are low and fluctuations in flow are infrequent. Although annual variability is high, during a typical rainy season base flows are higher and there are occasional peak flows. Peak flows generally last for a few days and gradually decline. During the rainy season, daily and weekly fluctuations in stream flow are huge. Life stages of stream organisms are timed to take advantage of this flow regime.

 

Table 23. Average monthly runoff at the Smith River gauging station from October 1, 1916 to October 1, 1966 (US Army Corps of Engineers 1971a).

Month

Average runoff

(acre/feet)

Average flow

(cubic feet/sec)

Percent of

annual runoff

October

73,000

1,200

3

November

252,000

4,200

10

December

423,000

6,800

16

January

485,000

7,800

19

February

407,000

7,000

16

March

362,000

5,800

14

April

276,000

4,600

10

May

171,000

2,800

6

June

74,000

1,200

3

July

31,000

500

1

August

20,000

300

1

September

19,000

300

1

 

Over the last 10,000 years, regional climatic conditions have fluctuated, implying that flood regimes have also varied. Historical records and geologic studies indicate that major floods occurred on the Smith River about 1600, about 1750, December 1861, January 1890, February 1927, October 1950, January 1953, November 1953, December 1955, December 1964, and January 1966 (McCain et al. 1995, Tables 24 and 25).

 

Table 24. Peak flows listed in order of magnitude on the Smith River near Crescent City, Del Norte County, California (US Army Corps of Engineers 1971a, USGS 1997).

Month and year

Flow (cfs)

December 1964

228,000

January 1972

182,000

December 1861

165,000

December 1955

165,000

January 1890

152,000

February 1927

152,000

October 1950

152,000

January 1966

145,000

November 1953

141,000

January 1953

139,000

March 1975

129,000

January 1971

128,000

December 1945

123,000

January 1970

118,000

January 1990

113,000

December 1962

113,000

November 1988

111,000

November 1973

106,000

December 1977

102,000

 

Table 25. Peak flows on the Smith River near Crescent City, Del Norte County, California, from 1932 to 1994. Flood stage is about 116,000 cfs. (US Army Corps of Engineers 1971a, USGS 1997)

Date of peak

Discharge (cfs)

 

Date of peak

Discharge (cfs)

March 18, 1932

61,700

 

November 8, 1963

89,200

January 2, 1933

51,500

 

December 22, 1964

228,000

January 14, 1934

33,100

 

January 6, 1966

145,000

November 1, 1934

33,900

 

January 28, 1967

87,800

January 14, 1936

55,500

 

February 23, 1968

77,800

April 13, 1937

70,100

 

February 13, 1969

69,400

December 11, 1937

78,900

 

January 23, 1970

118,000

March 12, 1939

41,800

 

January 16, 1971

128,000

February 28, 1940

37,200

 

January 22, 1972

182,000

December 20, 1940

44,100

 

December 22, 1972

49,800

December 18, 1941

62,400

 

November 15, 1973

106,000

December 31, 1942

91,400

 

March 18, 1975

129,000

November 4, 1943

40,600

 

February 26, 1976

45,400

February 8, 1945

56,500

 

September 28, 1976

15,800

December 28, 1945

123,000

 

December 14, 1977

102,000

November 18, 1946

50,000

 

January 11, 1979

80,300

January 6, 1948

83,100

 

November 24, 1979

76,500

February 22, 1949

48,800

 

December 2, 1980

74,800

January 18, 1950

91,400

 

December 19, 1981

89,600

October 29, 1950

152,000

 

March 30, 1983

88,400

February 1, 1952

61,500

 

February 13, 1984

72,500

January 18, 1953

139,000

 

November 12, 1984

55,700

November 23, 1953

141,000

 

February 22, 1986

96,800

December 31, 1954

70,200

 

February 2, 1987

42,400

December 22, 1955

165,000

 

December 10, 1987

76,900

February 26, 1957

67,100

 

November 12,1988

111,000

January 29, 1958

94,300

 

January 8, 1990

113,000

January 12, 1959

90,400

 

March 4, 1991

52,700

February 8, 1960

74,300

 

April 16, 1992

31,700

November 24, 1960

69,200

 

January 20, 1993

76,400

November 23, 1961

71,800

 

December 8, 1993

37,000

December 2, 1962

113,000

 

January 1997

Not available

 

The most famous peak flows occurred in 1955 and 1964. The '55 flood occurred on December 22, 1955. The flow at the Highway 101 bridge was estimated at 165,000 cubic feet per second. About 7,600 acres near the lower Smith River were inundated (US Corps of Engineers 1971).

In late December of 1964, the most severe flood since European-American settlement occurred when a warm moist air mass collided with cold air over the coast ranges. In nine days, thirty four inches of rain were recorded at Idlewild Maintenance Station in the upper Middle Fork area (California Department of Water Resources 1970). On December 22, 1964, stream flow peaked at about 250,000 cubic feet per second at the Highway 101 bridge. Non-damaging capacity at this location is 80,000 cubic feet per second (California Department of Water Resources 1970). About 9,300 acres of agricultural lands were flooded. The 1955 and 1964 floods triggered numerous landslides, including a forty acre slide in the South Siskiyou Fork basin (California Department of Water Resources 1970). Another high flow occurred in 1972 although this flood did not achieve notoriety.

The lowest recorded flows at the main gauging station on the lower Smith River were 160 cubic feet per second on October 25,1964 and 168 cubic feet per second on October 31, 1931. From 1932 to 1959, the discharge was greater than or equal to 200 cubic feet per second 98.5% of the time (California Department of Water Resources 1970).

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