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CAUSES OF PEAK FLOWS IN NORTHWESTERN MONTANA AND NORTHEASTERN IDAHO 1
Author(s) -
MacDonald Lee H.,
Hoffman James A.
Publication year - 1995
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.1995.tb03366.x
Subject(s) - snowmelt , water year , snow , drainage basin , spring (device) , environmental science , hydrology (agriculture) , flood myth , structural basin , climatology , atmospheric sciences , geology , geography , geomorphology , engineering , mechanical engineering , cartography , geotechnical engineering , archaeology
Both catchment experiments and a review of hydrologic processes suggest a varying effect of forest harvest on the magnitude of peak flows according to the cause of those peak flows. In northwestern Montana and Northeastern Idaho, annual maximum flows can result from spring snowmelt, rain, mid‐winter rain‐on‐snow, or rain‐on‐spring‐snowmelt. Meteorologic and physical data were used to determine the cause of annual maximum flows in six basins which had the necessary data and were smaller than 150 mi 2 . Rain‐on‐spring‐snowmelt was the most frequent cause of annual maximum flows in all six basins, although there was a strong gradient in the magnitude and cause of peak flows from southwest to northeast. Less frequent mid‐winter rain‐on‐snow events caused the largest flows on record in four basins. Mid‐winter rain‐on‐snow should be distinguished from rain‐on‐spring‐snowmelt because of differences in seasonal timing, the relative contributions of rain vs. snowmelt, and the projected effects of forest harvest. The effects of mixed flood populations on the flood‐frequency curve varied from basin to basin. Annual maximum daily flows could not be reliably predicted from rainfall and snowmelt data.