The channel-geometry method is an indirect method of flood estimation which relies on the development of relations between flood discharges, measured at gauging stations, and channel dimensions, measured from natural river reaches in the vicinity of the gauge. Channel-geometry equations enable flood discharges to be estimated at ungauged locations on natural streams from measurements of channel size and by combining the index flood estimate (usually the mean annual flood) with regional flood growth factors. This paper reports on channel-geometry equations which have been developed and applied in four developing, tropical countries as part of hydrological investigations for road design and flood risk assessment (Java), irrigation and hydropower development (Burundi), design of all-weather roads (Ghana), and rehabilitation of railway bridges (Tanzania). The applications demonstrate the benefits of the channel-geometry method in situations where data on catchment characteristics are limited or may not offer the most appropriate basis for flood discharge estimation.