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Spring/Summer 1996 WATER TALK Page 5 i ~ - ~, ~, ,y ~~ ~'" time was. 600 cubic feet per second (CFS) ,~ ~ - ~ } ~- y~,~.= "~ less than 17 years earlier, when it reached `Y~' ~~.,~,"~'" ~` ' .. -.~'~`,. -~ 3 700 CFS. ~ ~~ _ u'' ,. ' . _~ ~,~ \t;h .. ~ ~ ~: - -, '~ ~- - -. _ - f r~~ Photo caurtesy of theWan•an Sheaf ...cantinued from previous page ~-, ~.. --;,. .~ _ t~ ~; (Later talk of that incident may have been the source of a persistent Honor -unfounded -that this bridge or one of the others in Warren had been destroyed by the flood.) Ron Adrian, engineer for the Middle River- Snake River Watershed District, says he has a theory as to why the Snake rose so quickly and to such surprisingly high levels. Adrian says the upstream drainage area had 4.5 inches of moisture on the ground prior to the flood. There was some snow melting in the days leading up to the flood, but temperatures were 10-15 degrees below normal, causing a slow melt. While water from melting snow on open fields moved toward the ditches, Adrian believes that snowmelt occurring on CRP land and in the woods was largely retained by the remaining unmelted snow, creating saturated snow in those areas. On Wednesday, April 17, 1996 the tempera- lure shot up to 65 degrees, causing remaining snow on the open fields to melt, creating the surge in Snake River levels that evening. The next day, the tempera- tures again reached 65 degrees, Adrian notes, unlock- ing the water retained. in woods and CRP and causing the second, more damaging surge in river levels beginning late Thursday night and culminating in the peak level of 851.7 feet beginning at 5 a.m. Friday. Comparisons between the 1979 Warren flood and the Flood of `96 are inevitable, beginning with the fact that they both began on April 18. The `96 flood crested six tenths of a foot higher than the `79 deluge. However, notes Adrian, the peak flow this A second, more severe flood hit Warren Saturday, May 18, 1996, leaving behind a far larger clean-up job than the spring snow-melt flood that swept into town exactly a month earlier. This second flood ,~,,~ occurred 100 years to the day after another major rainstorm flood. The May 18 flood ~, ~` resulted from heavy rains upstream on the w ~~ Snake River the evening of Thursday May 16, 1996 and the night of Friday May 17, 1996, producing a river crest of 853.7 feet, a full 2 feet higher than the crest of the April 18-19 flood and within about half a foot of matching the flood of record in Warren. According to the Warren Shea}; the strongest part of the storm system reached Warren about 2:00 a.m. Friday, bringing high winds and heavy rain. While 3.7 inches of rain was reported at Warren, levels of up to 6.25 inches fell west of Warren. In Warren, the Friday morning downpour sent the Snake River above the flood stage mark of 845 feet. That afternoon and evening, river levels went down, dropping about three feet from mid-afternoon to midnight. At midnight, however, the river level began climbing again, the result of local heavy rains that started about 9:00 p.m. Friday and runoff from the east moving downstream. Although the amounts of rain Friday night generally were less than. the night before, the heavy showers added 1-2 inches of additional moisture in the Snake River drainage. The river at Warren continued rising until cresting at 2 a.m. Sunday. City officials estimated 80-90 percent of the homes in Warren had some flood impact from. the May 18 event. In most cases, damages were limited to partially or fully flooded basements, but the number of homes with water on the first floor was likely to be more than in the earlier flood. The City of Warren has considered flood control measures in the past. However, local opposi- tion and roughly 10 years without flooding had temporarily quieted discussion and support for such projects. The floods of 1996 have sparked a renewed interest in flood control, flood protection, and flood damage reduction projects for the City of Warren.