Appendix A: A Practical Guide to Effective Discharge Calculations
Long-channel Variation in Bank Top Elevations: Lower Mississippi in
Study Reach (adapted from Biedenharn and Thorne, 1994).
Application 1: Engineering-geomorphic Study of the River Blackwater, UK
The need for morphological studies to support sustainable engineering and management of rivers
is now generally accepted (Gardiner, 1991; Downs and Thorne, 1996). Calculation of the effective
discharge and application of the principles of hydraulic geometry analysis can be useful in developing a
sound understanding of the morphological status and stability of an alluvial stream, as a component in an
engineering-geomorphic study. The utility of this approach can be illustrated using a case study of the River
Blackwater, UK. The study is reported in detail in a report by Wallingford (1992) and summarized in a
paper by Thorne et al. (1996).
The River Blackwater is a lowland stream in southeast England. In the 1960s and 1970s the
channel was modified by engineering works installed as part of a series of flood defence and land drainage
schemes. Subsequently, the channel required a heavy maintenance regime to maintain a sufficient capacity