Aseawall with an opening is used to dampen the tidal influence in a coastal area (and limit erosion). the seawall is 2.5 m long (in the direction perpendicular to the page), the mean sea level on the sea side is 2.2 m above the centroid of the slot. the mean sea level on the land side of the wall is 1.4 m above the centroid of the slot. the sea side tide fluctuates +0.6 m, and the landward tide fluctuates +0.4 m.
the slot extends the entire length of the wall and is estimated to have a discharge coefficient of 0.80.

if the volume of seawater moving from the sea side to the land side of the wall is to be no more than 6 000 m' in 18 hours, what is the maximum allowable height of the slot?

note: the discharge coefficient is the ratio of the actual flow rate over the predicted flow rate. it mostly accounts for the fact that the average velocity is different from the velocity.