Another New Year's Eve Freshet

RWSERVE SystemD Journald server service System software SystemD [installation · systemd] This note documents how to use the SystemD service manager to enable unattended background execution of the server software, and how to use the JournalD service to view and manage the server's logged output.

Historic comparison

Comparison of floods is a favorite topic for the layman, with superlatives casually thrown around. The so-called 100-year flood is also a frequent topic for discussion. But the December 31, 2005 flood was remarkable, no matter how it is compared, and there are many lessons to be learned.

My own assessment of the “historic” nature of the New Year’s Eve Flood, is attempted using two different methods for comparison. The first is to compare the FEMA-defined extended floodplain—the so-called 500-year floodplain—to the maximum elevation attained on December 31st. The second is to compare discharge readings of a select gauge on the Russian River near Guerneville.

Map of historic comparisonThe comparison of the FEMA-defined extended floodplain is shown in the accompanying map. As it can be readily seen, areas in the south, near the Meadowlane Ponds, and near Rohnert Park and Cotati, are all much wider in extent than previously thought. The size of this floodplain, 611 acres, is significant.

In the northern part of the watershed, the December 31st floodwater extent falls short of the FEMA-defined boundary.

For comparing historic discharge readings, the Russian River gauge near Guerneville was chosen because it is the only one that has a continuous multi-decadal record (still it should be noted that the gauge was moved to a new site in 1963, making strict comparison somewhat inaccurate.)

Water

year

Event

date

discharge

(ft3/sec)

stage

(feet)

1940

02/28/40

88400

1941

04/05/41

48100

1942

02/06/42

67800

1943

01/22/43

69200

1944

03/04/44

32000

1945

02/01/45

34600

1946

12/28/45

56800

1947

02/12/47

23600

1948

03/24/48

23400

1949

03/12/49

41400

1950

02/05/50

44900

1951

12/04/50

53600

1952

12/28/51

41300

1953

01/10/53

52200

1954

01/17/54

59900

1955

12/06/54

13500

19.32

1956

12/23/55

90100

49.7

1957

02/25/57

45800

33.77

1958

02/25/58

68700

42.95

1959

02/16/59

48900

35.98

1960

01/31/60

63100

40.8

1961

01/31/61

33100

29.73

1962

02/13/62

57400

28.91

1963

02/01/63

71800

43.7

1964

01/21/64

33400

29.88

1965

12/23/64

93400

49.6

1966

01/05/66

77000

45.28

1967

01/21/67

68400

42.45

1968

01/30/68

40600

32.22

1969

01/14/69

68600

42.52

1970

01/24/70

72900

43.95

1971

12/04/70

59800

39.33

1972

12/27/71

8990

14.71

1973

01/12/73

62800

40.56

1974

01/17/74

74000

43.18

1975

02/13/75

67300

37.97

1976

03/01/76

5260

11.74

1977

03/16/77

1370

7.5

1978

01/17/78

65200

40.73

1979

01/11/79

26200

24.93

1980

01/14/80

59700

37.46

1981

01/28/81

35200

27.95

1982

12/20/81

67200

40.09

1983

01/27/83

71900

41.63

1984

12/25/83

55200

35.79

1985

02/08/85

28500

25.1

1986

02/18/86

102000

48.56

1987

03/13/87

26000

24.34

1988

01/04/88

35300

28.35

1989

03/19/89

23800

25.42

1990

01/14/90

18000

20.34

1991

03/04/91

48500

33.32

1992

02/20/92

28000

25.29

1993

01/21/93

55100

37.79

1994

02/20/94

14700

19.43

1995

01/09/95

93900

48.01

1996

02/05/96

49200

35.21

1997

01/01/97

82100

44.99

1998

02/03/98

56100

38.66

1999

02/09/99

37800

31.86

2000

02/14/00

37900

31.89

2001

03/05/01

24700

24.15

2002

01/03/02

44000

33.43

2003

12/16/02

57600

36.48

2004

02/18/04

63400

38.17

2005

12/28/04

21900

22.78

2006

01/01/06

86000

44.26

2007

02/11/07

29800

26.42


At the extreme, there have only been five recorded floods—since recordkeeping began at that station in 1940—that have exceeded the volume of water recorded during the New Year’s Eve Flood of 2005. These occurred on January 9, 1995; February 18, 1986; December 23, 1964; December 23, 1955; and February 28, 1940.

Some historic floods were more severe than recent floods because we now have a series of reservoirs that can hold water back for later release. They include:

  • Santa Rosa Creek Reservoir (a.k.a. Spring Lake)—which retains water diverted into it from Santa Rosa Creek—was completed in 1964.
  • Matanzas Creek, Piner (on Paulin Creek), and Brush Creek reservoirs were constructed in the late 1960s.
  • The Warm Springs Dam, which retains water in Lake Sonoma, was completed in 1983.
  • Since the completion of these flood control projects only two events have exceeded the intensity of the December 31, 2005 event.

Perhaps more informative than superlatives is the periodicity of floods of similar size. I’ve chosen the value of 68,800 ft3/sec (discharge) as one such threshold. This represents all floods at 80% or more of the size of the New Year’s Eve Flood. These have occurred 13 times in the past 69 years (water years 1940, 1943, 1956, 1963, 1965, 1966, 1970, 1974, 1983, 1986, 1995, 1997, 2006), a periodicity of once every 5 years.

I’ve also chosen the value of 77,400 ft3/sec as a threshold. This represents all floods at 90% or more of the size of the New Year’s Eve Flood. These have occurred 7 times in the past 69 years, (water years 1940, 1956, 1965, 1986, 1995, 1997, 2006) a periodicity of once every 10 years.

The periodicity of the New Year’s Eve Flood itself, at the threshold of 86,000 ft3/sec, which has occurred 6 times in the past 69 years (water years 1940, 1956, 1965, 1986, 1995, 2006), is once every 12 years.