Us Geological Survey

Salem West, Topographic Map Name ______

1. Find the Gaging station along the Willamette river just south of Center street. a) What is the elevation at the gaging station? ______b) What is the elevation of the gage datum (see the data sheet) ______c) What is the elevation of City Hall? (note: there are two City Halls. Refer to the southern one between the Library and the Fire Station) ______d) How high above the gaging datum would the river stage have to be to flood City Hall? ______e) Do you think a flood on the Willamette River could flood City Hall? ______f) What is the elevation of Memorial Hospital? ______g) How high above the gage datum would the river stage have to be to flood the hospital? _____ h) Do you think a flood on the Willamette River could flood the hospital? ______

We will now look at the last 114 years of peak discharge on the Willamette River and compute the discharges and river stages of the 10, 50, 100, and 500 year flood events. You will be able to prove (or disprove) your answer regarding flooding of the hospital and City Hall. On the back of this lab is the data from the gauging station that goes back to1881. 2. Complete the table on back by computing M and R. a) Rank the annual floods based on discharge from 1 to 114 (the first few are done for you). (NOTE: To save you time, you only need to rank the first 10) b) Compute the recurrence interval ‘R’ using the following formula: R=(N+1)/M where: N = number of years (in this case N=114) and M = rank (NOTE: After you complete these come check with me for the rest of the rankings)

3. Complete the following plots on the graph paper provided: PLOT A  Plot the Discharge vs. Recurrence interval (Note: pay close attention to the x-axis, this plot is semi-log graph paper)  NOTE: To save you time, you only need to plot the years that are in bold on the table.  Fit the best fit (straight) line through your data. DO NOT just connect the dots. PLOT B  Plot the Discharge vs. Stage.  NOTE: To save you time, you only need to plot the years that are in bold on the table.  Fit the best fit (curved) line through your data. DO NOT just connect the dots.

4. Using plot A - what is the discharge of the Willamette River during a: a) 10 year flood event ______b) 50 year flood event ______c) 100 year flood event ______c) 500 year flood event ______5. Using plot B - what is the river stage (above the datum and actual elevation) during a: Stage actual elevation a) 10 year flood event ______b) 50 year flood event ______c) 100 year flood event ______c) 500 year flood event ______6. On the map provided, shade in the entire area that would be flooded during a 100 year flood event. 7. BASED ON YOUR MAP is City Hall is likely to be flooded during a 100-year flood event? ______8. BASED ON YOUR MAP is the hospital is likely to be flooded during a 100-year flood event? ______PLOT A

700,000

600,000 700,000 500,000

600,000) s f c (

400,000 e

500,000g a ) r s a f 300,000 h c c ( 400,000

s i e g D r 200,000 a h 300,000 c s i

D 100,000 200,000

0 100,000 1 10 100 1000 Recurrence interval (years) 0 0 10 20 30 40 50 60 Stage PLOT B Station Description

STATION.--14191000 WILLAMETTE RIVER AT SALEM, OREGON

LOCATION.--Lat 44°56'40", long 123°02'30", in SE 1/4 SW 1/4 sec. 22, T.7 S., R.3 W., Marion County, Hydrologic Unit 17090007, on right bank 300 ft upstream from Center Street Bridge in Salem and at mile 84.16.

DRAINAGE AREA.--7,280 mi2, approximately.

PERIOD OF RECORD.--October 1909 to December 1916, January 1923 to current year. Monthly discharge only January 1923 to September 1927, published in WSP 1318. Gage-height records collected at about the same site since 1892 are contained in reports of National Weather Service.

GAGE.--Water-stage recorder. Datum of gage is 106.14 ft above sea level. Oct. 1, 1909, to Dec. 31, 1916, nonrecording gage at site 0.5 mi upstream at datum 8.00 ft higher. Jan. 1, 1923, to Nov. 26, 1934, nonrecording gage at Center Street Bridge at datum 8.00 ft higher. Nov. 27, 1934, to Sept. 30, 1962, water-stage recorder at present site at datum 8.00 ft higher.

REMARKS.--Flow regulated by 12 reservoirs upstream from station. Many small diversions for irrigation upstream from station; part of flow of Salem Canal, which diverts water from North Santiam River, returns to Willamette River downstream from station through Mill Creek at Salem.

AVERAGE DISCHARGE.--82 years (water years 1910-16, 1924-98), 23,470 ft3/s, 43.81 in/yr, 17,000,000 acre-ft/yr. 30 years (water years 1969-98) 23,850 ft3/s, 44.51 in/yr, 17,280,000 acre-ft/yr.

EXTREMES FOR PERIOD OF RECORD.--Maximum discharge, 348,000 ft3/s Jan. 8, 1923, gage height, 38.3 ft, present datum; minimum discharge, 2,470 ft3/s Aug. 27, 1940, gage height, 3.55 ft, present datum.

EXTREMES OUTSIDE PERIOD OF RECORD.--Maximum discharge, 500,000 ft3/s Dec. 4, 1861, gage height, about 47 ft present datum, from rating curve extended above 250,000 ft3/s in 1916. Floods of Jan. 16, 1881, and Feb. 5, 1890, reached stages of 44.3 ft, discharge, 428,000 ft3/s, and 45.1 ft, discharge, 448,000 ft3/s, respectively, from floodmarks and information by Corps of Engineers. US GEOLOGICAL SURVEY - PEAK FLOW DATA (Willamette River, Salem, OR) drainage area (square miles). . . 7280 gage datum (feet above NGVD) 106 Stage heights are given in feet above gage datum elevation.

Date Discharge Stage M R 11/26/1927 125000 24.7 1/30/1967 120000 23.3 (cfs) (rank) (years) 12/31/1928 73600 19.6 2/25/1968 92800 20.5 01/16/1881 428000 46 2 57.5 12/21/1929 115000 23.8 12/6/1968 106000 23 02/05/1890 448000 47 1 115.0 4/2/1931 220000 31.5 1/26/1970 135000 25.9 12/28/1892 136000 25.6 3/21/1932 172000 28.5 1/20/1971 142000 26.9 12/02/1893 252000 34.9 1/5/1933 115000 24.3 1/22/1972 180000 30.2 01/14/1895 165000 28.4 12/23/1933 175000 28.8 12/21/1972 84900 20.4 01/23/1896 176000 29.3 12/23/1934 119000 24.6 1/17/1974 206000 32.3 02/17/1897 136000 25.6 1/14/1936 225000 31.8 1/10/1975 83200 20.2 12/15/1897 137000 25.7 4/16/1937 201000 30.4 1/10/1976 122000 25 03/03/1899 165000 28.4 12/31/1937 186000 29.5 3/10/1977 33100 12 1/16/1900 178000 29.5 2/16/1939 95700 22.3 12/16/1977 148000 27.4 1/15/1901 329000 39.5 2/29/1940 100000 22.8 2/11/1979 78700 19.6 2/12/1902 122000 24.2 1/19/1941 74400 19.7 1/15/1980 12300 25 1/27/1903 283000 36.6 12/21/1941 132000 27.1 12/27/1980 140000 26.7 2/18/1904 155000 27.5 1/2/1943 291000 38.6 12/7/1981 136000 26.4 12/31/1904 113000 23.3 11/6/1943 63700 18.2 2/20/1983 107000 23.2 2/26/1906 92000 21.2 2/9/1945 104000 23.5 2/15/1984 106000 23.1 2/6/1907 325000 39.3 12/30/1945 255000 36.3 11/30/1984 93900 21.6 12/27/1907 224000 32.8 12/16/1946 240000 34.7 2/24/1986 152000 27.8 1/22/1909 185000 30 1/9/1948 242000 35.5 11/29/1986 99700 22.3 11/25/1909 315000 38.5 2/19/1949 184000 31.2 1/16/1988 106000 23.1 1/20/1911 155000 27.5 1/24/1950 153000 28.6 1/12/1989 92400 21.4 1/15/1912 221000 32.5 11/1/1950 159000 29.1 1/9/1990 82300 20.1 4/1/1913 158000 27.4 2/5/1952 143000 26.3 1/16/1991 69600 18.1 1/25/1914 123000 24.3 1/20/1953 251000 34.2 12/8/1991 73800 18.8 1/15/1915 98000 21.8 1/30/1954 153000 27.2 3/24/1993 83500 20.2 2/9/1916 242000 34 1/1/1955 107000 22.6 2/25/1994 60800 16.7 3/30/1917 90500 20.5 12/23/1955 240000 33.4 1/16/1995 125000 25.3 12/20/1917 217000 32 3/10/1957 129000 24.9 2/8/1996 244000 35 1/24/1919 172000 29 12/22/1957 151000 27 1/2/1997 170000 29.4 1/27/1920 118000 23.8 1/13/1959 130000 24.8 1/15/1998 90500 21.2 12/31/1920 158000 27.8 2/10/1960 106000 22.2 12/30/1998 162000 28.8 11/22/1921 219000 32.6 2/12/1961 241000 33.5 11/27/1999 104000 23 1/8/1923 348000 38.3 3 38.3 12/22/1961 133000 25.1 12/24/2000 35700 12.7 12/8/1923 89200 21.4 5/8/1963 112000 22.8 1/27/2002 87100 20.8 2/6/1925 178000 28.7 1/21/1964 128000 24.6 2/1/2003 96200 22 2/8/1926 172000 28.3 12/23/1964 308000 37.7 12/15/2003 91200 21.4 2/23/1927 243000 32.7 1/7/1966 158000 26.8