If the approach velocity is not too high, a hump in the bottom of a water channel

Question:

If the approach velocity is not too high, a hump in the bottom of a water channel causes a dip Δh in the water level, which can serve as a flow measurement. If, as shown in Fig P3.175, Δh = 10 cm when the bump is 30 cm high, what is the volume flow Q1 per unit width, assuming no losses? In general, is Δh proportional to Q1? Fig P3.175

If the approach velocity is not too high