Found 16 River CC0 textures in library

Gravel 008

Gravel 016

Gravel 017

Gravel 018

Gravel 019

Gravel 020

Gravel 021

Gravel 035

Gravel 036 L

Gravel 036 S

Ground 021

Ground 022

River Phonix Marble

River Small Rocks

Rocks 024 L

Rocks 024 S