Turbulence in free-surface flows plays a fundamental role in environmental fluid dynamics, governing the transport of sediments, pollutants, and nutrients. A predominant fraction of turbulent kinetic energy and transport is conveyed by coherent structures, known as Large-Scale Motions (LSMs) and Very-Large-Scale Motions (VLSMs), massive turbulent aggregates extending over multiples of the bulk flow depth. Although extensively documented in canonical wall-bounded flows and laboratory channels, their field-scale experimental investigation is limited by operational complexities and instrumental noise. Consequently, the quantitative characterization of these dynamics in natural contexts remains an open research field. This thesis bridges this gap by investigating the kinematics and energetics of macro-turbulence in a free-surface flows under field conditions.