FLOOD07755

• County: Statewide
• Basin: Statewide
• Title: Engineering and Design Runoff from Snowmelt
• Date: 1/5/1960
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

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MANUALS-CORPS OF ENGINEERS
U,S. ARMY

EM Illl).-2-1406
5 Jan 60

ENGINEERING AND DESIGN

RUNOFF FROM SNOWMELT

CHAPTER 1

INTRODUCTION

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1 ~Ol.!PURPOSE AND SCOPE. This manual provides information on basic theory of snowmelt
and snowmelt rnnoff, together with procedures for applying the theory to basin snow hydrology
probll'ms involved in the design or operation of Corps of Engineers water control projects, There
are included two examples of project design floods involving snowmelt runoff which are developed
according t.o these proceuures.
Until recently, snowmelt runoff has been estimated by simple, empirical relationships, largely
because of the lack of adequate basic knowledge. An extensive cooperative research program
initiated by the Corps of Engineers and U.S, Weather Bureau in 1945 has led to formulation of
rational methods for solving these problems, but the results have not been made available in a
eondcnsl'd mannal form. Aecordingly, a synopsis of certain basic relationships developed in those
investigations is included in this manual.

1~02. REFERENCES. The techniques described herein are derived principally from the summary
report of the sno\'" invest.igations entitled, "Snow Hydrology," published by the North Pacific Di-
vision Office of the Corps of Engineers, and dated 30 June 1956, The reader is referred to the
abo,'c summary report for basic reference material and more detailed discussions of the subject,
A seleded bibliography of literature pertaining to streamflow computations from melting snow is
contained in arpcndix I of this manual. References in the manual text to items in the bibliography
arc indicated by the numbers in an exponential position. A comprehensive listing of literature per-
t.aining to snow is cont.ained in a series of reports entitled, "Bibliography on Snow, Ice, and Perma-
frost," 14 published by the Snow, Ice, and Permafrost Research Establishment, In addition,
reference is made to t.he following other manuals in this series:
E'.I 1110~2~1405, Flood-Hydrograph Analysis and Computations,
E'.l 1110-2-1408, Routing of Floods Through River Channels.
E'.I 1110-2--1411, Civil Works Engineer Bullet.in 52-8, "St.andard Project. Flood Determina-
tions," 26 "larch 1952,
E~I 1110-2-3600, Reservoir Regulation,

1-03. DEFINITIONS. Definit.ions of technical terms are given in the general presentat.ions of t.he
theory in the manual. A glossary of t.erms and their symbols is presented in appendix II,

1-04. GENERAL. :\Ielting snow is a factor affecting runoff which may be an important consider-
ation in dl'sign flood analysis. In some rivers, snowmelt constitutes the major source of runoff,
while in ot.her drainages its importance is secondary t.o the cont.ribut.ion from rainfall, In either
case, t.he evaluat.ion of snowmelt runoff is a complex problem, and snowmelt comput.at.ions should
be made on a rational basis. Unlike rainfall, snowmelt is not a measured quantity in hydrologic
prnctice, and it must be estimated indirectly from metcorologicll.l parameters. Snow hydrology,
in relation to llood hydrograph analysis, involves primarily the determinat.ion of snowmelt rates
under variolls conditions of t.errain, veget.al cover, and weather, Secondly, it involves evaluat.ion
of the dToct of the snowpack on runoff. A third major division of snow hydrology is concerned with

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