Bottom drag coefficient is usually estimated from vertical structures of horizontal flows. Analytic models have demonstrated that bottom friction causes cross channel variations of velocity such that the amplitude of the along channel velocity increases with depth, and the velocity in shallow water has a phase lead, i.e. flood and ebb occur earlier in shallow water along the same cross channel transect. Based on these facts, we have developed a simple method to estimate the drag coefficient using lateral flow structure. The method is verified by data from a vessel-towed acoustic Doppler current profiler (ADCP) in unstratified tidal channels of Georgia, US. The cross channel average of the drag coefficient is 4.55 ¿ 10-3 (1 ¿ 18.6%), a reasonable value compared to previous results.