Appendix A: A Practical Guide to Effective Discharge Calculations
Woodyer, K. D. (1968). Bankfull frequency in rivers. Journal of Hydrology, 6:114-142.
Yevjevich, V. (1972). Probability and Statistics in Hydrology. Water Resources Publications, Fort Collins,
APPENDIX II. GLOSSARY
1.58-Year Return Period Discharge (Q1.5) - The discharge with a return period of 1.58 years, derived
from the observed annual maximum flow series. Results of research on the use of Q1.5 in dominant
discharge analysis are reported by Hey (1975) for the UK and Leopold et al. (1964) for the USA.
2-Year Return Period Discharge (Q2) - The discharge with a return period of 2 years, derived from
the observed annual maximum flow series. Results of research on the use of Q2 in American rivers are
reported by Biedenharn et al. (1987).
Bankfull Discharge (Qb) - The maximum discharge which can be contained within the channel without
over-topping the banks. Leopold et al. (1964) proposed that it is this flow which is responsible for forming
and maintaining the morphology of the channel. Bankfull stage refers to the water surface elevation during
bankfull flow and can be identified from various criteria (Williams, 1978). Research papers reporting the
use of Qb include: Leopold and Wolman (1957), and Andrews (1979) in the USA; and Charlton et al.
(1978), and Hey and Thorne (1986) in the UK.
Bed Load - A component of the total sediment load made up of sediment particles moving in frequent,
successive contact with the bed (Bagnold, 1966). Transport occurs at or near the bed, with the submerged
weight of particles supported by the bed. Bed load movement takes place by gravitational processes of
rolling, sliding or saltation.
Bed Material Load - A portion of the total sediment load composed of grain sizes found in appreciable
quantities in the stream bed. In gravel-bed rivers the bed material load moves as bed load, but in sand-bed
streams significant quantities of bed material load move as suspended load.
Channel Forming Discharge - The discharge that most efficiently drives the fluvial processes
responsible for forming and maintaining the main morphological features and dimensions of the channel.
Synonymous with dominant discharge.
Design Discharge - The steady discharge used in the engineering design of a stable channel or flood
defence scheme to define the upper boundary of the operating range of discharges for the project.
Discharge - The volume of water passing through a cross-section in a stream per unit time. It is usually
expressed in cubic metres or cubic feet per second.