This is a big problem in India too. Many of the rivers in Kerala state have been impacted by illegal sand mining. We had rarely used property next to the river which we sold to a relative who had a house next to ours. They fell on hard times and sold it to someone else who discovered the sand and started mining the land ($$$$). That land, the house, the large jackfruit and coffee trees are no more; in its place is a huge indentation in the landscape where the river would fill if there was enough water. The rest of the river has very little sand in it as a result of mining. Natural flooding is now very rare. It has been reduced to a sliver of its former self.