animals hike Piedra River river rocks squirrel trail brown green Oak Trees pine trees reflections River Banks rust garden gardening geology landscape landscaping pebble pebbles piedra piedras river bed rock stone stones texture textures blue bushes gray guardrail highway mountains River Grass shrubs Tan white Merced river national park nature pines riverbanks summer trees usa valley Yosemite alps bavaria creek forest germany Mountain River outdoor rainy water wather bedrock cobble cobbles ground solid passage stream exposure waterfall