Thursday, 26 January 2017: 3:45 PM
609 (Washington State Convention Center )
River flooding and flash flooding are a significant threat to life and property across the United States. Millions of dollars are lost each year due to flooding. Flash flooding results from heavy rain in a single day while river flooding occurs due a melting snow pack, multiple days of heavy rain, or both. Identifying trends in total precipitation and extreme daily precipitation can identify not only what portions of the country are becoming increasingly threatened by flooding but at what time of the year these trends are most pronounced. Precipitation data from over 240 individual stations across the northern and central plains are examined to identify if there are statistically significant trends in extreme daily precipitation and total precipitation over a 30-, 60- and 90-day period from the early 20th century through 2013. When examining individual stations, differences in precipitation trends are observed spatially and temporally. During the late winter and early spring, total precipitation over a 90-day period is increasing at over 50 mm per century in parts of eastern Nebraska, Iowa, southeastern South Dakota and Minnesota. The increase in total precipitation corresponds to an area where an increase in springtime river flooding has also been observed. With the exception of parts of Iowa, significant trends in total 90-day precipitation were not observed over the eastern Plains during the mid and late summer but were found over the western Plains. Examining trends in extreme and total precipitation at individual stations on smaller time scales can be used to find both specific time periods and areas where significant trends in precipitation are increasing the risk of flooding.
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