  We study the effect of galactic outflows on the Lya forest. The winds are
modelled as fully ionised spherical bubbles centered around galactic haloes.
The observed flux probability distribution and flux power spectrum limit the
volume filling factor of bubbles to be less than 10%. We have compared the mean
flux as a function of distance from haloes with the Adelberger etal (ASSP)
measurement. A model with bubbles of constant radius of 1.5Mpc/h surrounding
the most massive haloes matches the high transmissivity at separations
<0.5Mpc/h, but the increase of the transmissivity at small scales is more
gradual than observed. At separations <0.5Mpc/h, our estimate of the cosmic
variance error is $\Delta F\sim 0.3$, 30% higher than that of ASSP. The
difficulty in matching the rise in the transmissivity at small separations is
caused by residual absorption of neutral hydrogen lying physically outside the
bubbles but having a redshift position similar to the haloes. The flux level is
thus sensitive to the amplitude of the coherent velocity shear near haloes
which increases with halo mass in the simulation. A model where LBGs are
starbursts in small mass haloes matches the observations with smaller bubble
size than one where more massive haloes host the LBGs. A starburst model with a
bubble radius of 1Mpc/h and a volume filling factor of 2% is consistent with
the ASSP measurements at the 1-1.5$\sigma$ level. If this model is correct the
sharp rise of the transmissivity at small separation in the ASSP sample is due
to cosmic variance and is expected to become more moderate for a larger sample.
