  We measure electron transport through point contacts in an electron gas in
AlGaAs/GaAs heterostructures and graphene for a range of temperatures, magnetic
fields and electron densities. We find a magnetoconductance peak around B = 0.
With increasing temperature, the width of the peak increases monotonically,
while its amplitude first increases and then decreases. For GaAs point contacts
the peak is particularly sharp at relatively low temperatures $T\approx$1.5 K:
the curve rounds on a scale of few tens of $\mu$T hinting at length scales of
several millimeters for the corresponding scattering processes. We propose a
model based on the transition between different transport regimes with
increasing temperature: from ballistic transport to few electron-electron
scatterings to hydrodynamic superballistic flow to hydrodynamic Poiseuille-like
flow. The model is in qualitative and, in many cases, quantitative agreement
with the experimental observations.
