Extreme Value Snow Water Equivalent and Snowmelt for Infrastructure
Design over the Contiguous United States
Abstract
Snowmelt-driven floods result in large societal and economic impacts on
local communities including infrastructure failures in the U.S. However,
the current U.S. government standard design precipitation maps are based
on liquid precipitation data (e.g. National Oceanic and Atmospheric
Administration’s Precipitation-Frequency Atlas 14; NOAA Atlas 14) with
very limited guidance on snowmelt-driven floods. In this study, we
developed 25- and 100-year return level design maps of snow water
equivalent (SWE) and 1-day and 7-day snowmelt including precipitation
events (e.g. rain-on-snow) using long-term observation-based gridded SWE
developed by University of Arizona (UA) incorporating the national snow
model product (SNOw Data Assimilation System; SNODAS) over the
contiguous U.S. (CONUS). For the 44 U.S. states where the NOAA Atlas 14
maps are available, the design snowmelt values from this study exceed
the standard design values in 23% of the total extent. The snowmelt
values exceed the NOAA Atlas 14 design precipitation by up to 171 and
254 mm in the northeastern U.S.; 127 and 225 mm in the north-central
U.S.; and 191 and 425 mm the western mountain U.S. for the 25- and
100-year return levels, respectively. A comparison of 7-day design
snowmelt between with and without precipitation shows that including
precipitation results in an average increase of 42 mm and 68 mm for 25-
and 100-year return levels, respectively, over snowmelt that do not
include precipitation. The design snowmelt maps from this study
complement the NOAA Atlas 14 design precipitation and provide additional
guidance on infrastructure design for snowmelt-driven floods in the
CONUS.