The riparian zone is the lakes filter between land and water. The grass is growing because nutrients are available for it to grow. It's absorbing materials that would increase weed growth in the pond if you remove it. If you still want a sandy shore you may be best to choose a small section of lake frontage and bring in a few loads of sharp sand to smoother it.

As for the swamp, if you want water you'll need to dig it out. Don't use Roundup near water bodies.

Dan O.