What is defined as a large rock transported by a stream?

The term "boulder" specifically refers to a large rock that has been transported by a stream or a river, typically measuring more than 10 inches in diameter. This classification is important in geomorphology and sedimentology, as boulders have distinct characteristics and behaviors compared to smaller rock fragments. Their size makes them more resistant to erosion and movement, often resulting in a significant impact on the landscape and stream dynamics.

In the context of erosion, sediment, and stormwater management, recognizing what constitutes a boulder as opposed to smaller sediment particles—like shingle, granule, or stone—is vital for understanding how these materials influence drainage patterns, sediment transport, and the overall health of aquatic ecosystems. The size and weight of boulders can also affect water flow and habitat creation or destruction, making their identification crucial for environmental assessments and construction projects near water bodies.