“…If this potential can be realized, passive optical remote sensing could complement other methods for noncontact flow measurement. Current approaches include large‐scale particle image velocimetry (PIV) using foam or other debris captured by video [e.g., Muste et al , ; Lewis and Rhoads , ; Tauro et al , ] or thermal signatures [e.g., Puleo et al , ; Dugan et al , ], various forms of radar [e.g., Costa et al , ; Fulton and Ostrowski , ], and airborne acoustic measurements of surface roughness [ Krynkin et al , ]. The ability to estimate velocities from optical, thermal, radar, or acoustic data could enable remote measurement of river discharge, provided depth information also can be obtained via remote sensing or some other independent means; this is an important and long‐standing objective in the hydrologic sciences.…”