Constructing or raising a structure on an available vacant land which actually do not belong to you is nothing but an act of encroachment.
The encroachment may be considered as an offence under anti land grabbing act too,
To whom does this land belongs?
Did you obtain permission or a NOC from the owner of the vacant site, it may be even your own society or the neighboring society?
If you have not obtained permission or NOC but have built a wall or any structure on the vacant land not belonging to you, it may be termed as an illegal structure and liable to be demolished.
Even now, you may obtain permission for the owner and agree to arrange for easy passage of the water logging , and remove the obstruction obstructing the free flow of water even during heavy rains.
Since you are at fault, an amicable settlement shall be the best solution for this.