Simplify the following text for a Grade 10 native English-speaking person.
Original: Riverina soils are generally sandy along the river channels , with more saline gray and brown clays found on rarely flooded areas on the perimeter of the floodplain .
Simplified: Riverina soils are generally sandy along the rivers , with more saline gray and brown clays found on rarely flooded areas on the edge of the floodplain .