An arroyo (/ ə ˈ r ɔɪ oʊ /; from Spanish arroyo Spanish: , "brook"), also called a wash, is a dry creek, stream bed or gulch that temporarily or seasonally fills and flows after sufficient rain. Flash floods are common in arroyos following thunderstorms.

Arroyo Grande is located in a coastal ecosystem within the California floristic province, and the native habitats include coast live oak woodland, central coastal scrub, willow and mixed riparian along Arroyo Grande Creek and numerous tributaries, native bunch-grass grassland, coastal prairie, dunes and intertidal zone, and non-native and ...