The screen/rack in front of your tube is a good idea, but make sure to check on it during heavy rains. It looks like you should have a good seal around your pipe with all the concrete. On one of our bigger dams we encapsulated the first half of the plastic tube within a concrete casing. On the downstream end of your tube, make sure you place some rock and rubble to absorb the impact of the water flowing through the tube, as it will speed up as it passes through.
