Although Acoustic Backscattering Systems (ABS) working in MHz range have proven their potential for small-scale flow studies under laboratory and field conditions, they are still subject to significant errors in the upper range of the turbulent energy spectrum (Thorne and Hanes 2002). Two novel methods improving the inversion of incoherent intensity and coherent pulse-to-pulse Doppler phase shifts will be proposed and discussed: (a) the first method increases the stability of the inverted sediment concentration profile in the case where acoustic intensity attenuation can not be ignored such as observed in highly turbulent benthic regions. (b) The second one allows increasing the SNR in the turbulent energy spectra by suppressing that fraction of the Doppler noise which affects the inertial subrange. Both methods use quasi-simultaneous and co-located bi-frequency information obtained with a single emitter and a versatile hardware system. Validation experiments with fine particle suspensions are conducted in open-channel flows and for grid generated turbulence in a mixing box. The capacity of multi-frequency ABS to profile turbulent erosion fluxes is demonstrated.