That's a possible concept but some gov't agency will have to monitor the gravel extraction. An operator could easily excavate too much material in the wrong location and cause flooding and damage downstream. Then people will be on here complaining about how stupid the gov't and contractors were for causing the damage even if it is 20-30 yrs later. Then there is the operations. How do you excavate gravel efficently and cost effectively if your equipment is in constant danger of being flooded out. It can be done and is done successfully in other areas of the state but it's more complicated than most realize and there is liability that goes along with it.