Composed of unconsolidated sediments, they are rapidly eroded during floods and high flows of water, or they may be the site on which new layers of mud, sand, and silt are deposited.
(they; are rapidly eroded; T:during floods and high flows of water) (they; may be; the site on which new layers of mud, sand, and silt are deposited) (new layers of mud, sand, and silt; are deposited; L:the site)
they they new layers of mud, sand, and silt
are rapidly eroded may be are deposited
T:during floods and high flows of water
the site on which new layers of mud, sand, and silt are deposited
L:the site