Historical High Water Events - @Vancouver Gage 45 and Willamette River @Morrison Gage Columbia River 40 Elevation

35 Willamette River Elevation

30 NAVD88

- Columbia River 25 1%-Annual- Chance Event 20 Columbia River 15 0.2%-Annual- Chance Event

Water Elevation Elevation Water 10 Willamette River 1%-Annual- 5 Chance Event Willamette River 0 0.2%-Annual- 2/6/1890 6/7/1894 6/1/1948 6/4/1956 12/25/1964 2/9/1996 Chance Event Date February 1890 Flood Event Unusually heavy precipitation was followed by heavy snowmelt in the . This flood’s inundation area has been used by FEMA as the base floodplain for parts of the Willamette. June 1894 Flood Event Heavy precipitation throughout the Columbia River basin during the 1893-94 winter led to heavy snowpack. This was followed by a dry, warm spring resulting in a massive snowmelt. There was still heavy rainfall in the lower basin, contributing to the flooding. Water levels remained at major flood levels (31.3+ NAVD88) for 38 days.

May 1948 Flood Event Heavy precipitation in the Columbia River basin throughout the winter led to heavy snowpack. Early spring had little precipitation and few warm days. May brought heavy rainfall and warm temperatures, which created heavy snowmelt in late May causing flooding throughout the entire basin. Water levels remained at major flood levels (31.3+ NAVD88) for 26 days. Fifteen lives were lost.

June 1956 Flood Event Persistent heavy precipitation in the Columbia River basin started in October of 1955 through February of 1956. Heavy rainfall in the northern Columbia basin continued through March. Snowpack in higher elevations started by the end of October, and by springtime snowpack was much higher than usual. Warm temperatures in late spring augmented the snowmelt. Water levels remained at major flood levels (31.3+ NAVD88) for 12 days.

December 1964 Flood Event Unusual cold weather in early December was followed by heavy snowfall. Subsequently there was warm, persistent, heavy rains later in the month. This classic “rain on snow” flood affected all of , with nearly every river in the state flooding and over 30 major bridges impassable. December rainfall that year was more than 3.5” above average in the area. Water levels remained at major flood levels (31.3+ NAVD88) for 2 days.

February 1996 Flood Event The season had heavy precipitation and warmer temperatures earlier in the season throughout the Pacific . Floodwaters were fed by heavy rains and melting snow. The Portland Airport area received about 7 inches of rain in a four day period. The Willamette River reached 31 NAVD88 in height and crested the downtown Portland seawall (33.3 NAVD88). Several rivers, many in the northern Willamette Valley, set new flood stages. October 23, 2014 Historical High Water Events - Columbia River Historical High Water Events - Willamette @Vancouver Gage @Morrison Gage 45 45

40 40 0.2% - 500 yr 0.2% - 500 yr 35 35 1% - 100 yr 1% - 100 yr 30 30

25 25

20 20

15 15

10 10 Water Elevation in NAVD88 in Elevation Water 5 NAVD88 in Elevation Water 5

0 0 2/6/1890 6/7/1894 6/1/1948 6/4/1956 12/25/1964 2/9/1996 2/6/1890 6/7/1894 6/1/1948 6/4/1956 12/25/1964 2/9/1996 Date Date

COLUMBIA RIVER @VANCOUVER GAGE WILLAMETTE RIVER @MORRISON GAGE Date Water Elevation Current FEMA Annual-Chance Water Date Water Elevation Current FEMA Annual-Chance NAVD88 Surface Elevation NAVD88 Water Surface Elevation 2/6/1890* 29.3 Above 10% 2/6/1890* 33.7 Above 1% 6/7/1894* 39.7 Above 0.2% 6/7/1894* 38.0 Above 0.2% 6/1/1948 36.1 Above 0.2% 6/1/1948 35.0 Above 1% 6/4/1956 32.9 Above 1% 6/4/1956 33.0 Above 1% 12/25/1964 33 Above 1% 12/25/1964 36.4 Above 1% 2/9/1996 32.5 Above 1% 2/9/1996 35.2 Above 1% *No dams on Columbia River at this time **Vancouver gage data not available until 1902, source used: USACE CL-03-112

After 1973 no additional flood control projects on the Columbia River have been constructed. The Vancouver Gage is located downstream of Peninsula Drainage District #1 near the Port of Vancouver. Upstream elevations will be higher. The Willamette Gage is at the . Gage data obtained from the . Current FEMA elevations obtained from the 2010 City of Portland Flood Insurance Study from FEMA.