Runnel, rundle, rindle, runlet, streamlet, brooklet, tricklet, rivulet, rill— the mostly archaic names for small-channeled flowings of water abound, and they all contain the phonemes /l/ and /r/, known linguistically as “liquids,” which flow over and along the tongue like water on a smooth stone. All these terms can mean a little or tiny brook. Rivulet, which once meant “small river,” now sometimes denotes the slightly larger erosional channels formed by rills merging on a steep slope. Runnel can suggest the same—a small natural gutter—and has a specific geomorphic meaning: a trough, formed by wave action on the lower portion of a beach, which is submerged by the incoming tide and drains the beach as the tide ebbs.

John Daniel