Whenever any improvement constructed under this article is completed, it shall be under the control and supervision of the board of water management commissioners. It shall be the duty of said board to maintain the levees, ditches, drains, watercourses, floodwater retarding structures and any other improvements in good repair, and for this purpose the board of water management commissioners may annually levy a tax on the lands benefited by the construction of such improvement in the same manner as other water management taxes are levied, not to exceed 10 percent of the assessed benefits in any one year, and the fund that is collected shall be used for repairing and maintaining the ditches, drains, watercourses, floodwater retarding structures and other improvements in perfect order; provided, however, that if any repairs are made necessary by the act of negligence of the owner of any land through which such improvement is constructed or by the act of negligence of his agent, tenant or employee or if the same is caused by the cattle, hogs or other livestock of said owner, tenant, employee or agent, then the cost thereof shall be assessed and levied against the lands of the owner alone to be collected by proper civil action instituted by the water management commissioners; provided further, that when it shall become necessary to repair any railroad bridge or construct a new railroad bridge by reason of enlarging any watercourse or of excavating any canal intersection or by reason of wear and tear and natural deterioration of such bridge or structure, such repairs, maintenance and improvement shall be made at the expense of the said railroad. It shall be unlawful for any person to injure or damage or obstruct any improvements constructed under the provisions of this article without securing the prior written consent of the board of water management commissioners, and any person causing any injury, damage or obstruction or building any bridge, fence or floodgate without the consent of the board of water management commissioners shall be deemed guilty of a misdemeanor.