The entire area of the open drain between the yellow stakes is deemed to be the hazard not just the water so, even if your ball lands on the bank, you may still not ground your club or remove twigs etc. The stakes are movable obstructions so if they interfere with the ball or your stance you can move them without penalty.

If, whilst your ball lies within the hazard, you decide that any part of the bridge is obstructing your stance, swing or potential ball flight and you choose not to play the ball as it lies, you must drop the ball outside the hazard for a one shot penalty, (Rules of Golf 24.2.b states that “except when the ball is in a water hazard, a player may take relief from interference by an immovable obstruction”) i.e. there is no free drop if the bridge is in the way when you are in the water hazard.

If, however, whilst your ball is not within the hazard, any part of the bridge interferes with your normal stance or swing, you may drop the ball, as per rule, without penalty. This rule does not entitle you to a free drop if the bridge is merely within the flight path of your intended shot. (In such cases it is suggested that a suitable club be selected to successfully clear the obstacle.)

If your ball lies actually on the bridge (not in the hazard) you are permitted to drop the ball, as per rule, without penalty.