Formation and Propagation of Tidal Bore

In a tidal river, the peak value of the discharge occurs earlier than the peak value of the tidal elevation. The high water level of a tidal wave moves faster than the low water level, and as a result the slope of the wave-surface profile, in the direction of propagation, increases from high water to low and decreases from low water to high. This differential slope causes retention of tidal flux during ebb, which in turn elevates the low water level and introduces a delay in the occurrence of the low water phase. This delay causes the flood discharge, at the transition of flow from ebb to flood, to start with an initial value. During the passage of tides of large amplitudes, the delay angle and consequently the initial value of the flood discharge at the transition of flow from ebb to flood becomes large and generates a surge. This surge discharge, at the transition of flow from ebb to flood, generates the bore. This is possible only in rivers where the summation of the phase lead and delay angles exceeds π/2. The veracity of these computations is checked from observed data.