River remote sensing for setting-up quantitative hydromorphological rehabilitation targets (#34)
River
classification and the derived knowledge about river systems have so far been
based on discontinuous sampling along the river course through field works
and/or (subjective) interpretation of aerial images. Remote sensing data, since
some years, offer notable opportunities to change this paradigm enriching
traditional information with an unprecedented amount of spatially distributed
hydromorphological data.
A river characterization framework based on color infrared orthophotos
at 40 cm and a LIDAR derived DTM at 5 m acquired simultaneously in 2009-2010
have allowed to characterize the main river systems in the Piedmont Region
Italy (25400 kmq) with continuous information on areal and topographic
hydromorphological features. The framework by a semi-automated procedure delineates
the valley bottom of each river course and within this the active channel area
composed of water channels, unvegetated and vegeted sediment bars, and, if
present, islands. Using semi-automated segmentations of river courses and
statistical analyses of the derived regional database river functional types
have been quantitatively defined in terms of distribution of areal and
topographic features. Reference types have been identified within all the
functional types defined. Rehabilitation targets can then be defined for
hydromorphologically altered river segments, each of which can be associated to
a specific reference functional type based on case specific evaluations. In case of restoration projects the achievements of these targets can be monitored through planned
acquisition campaigns of RS data in order to measure river morphodynamic
trajectories over years and so assess the rate of success of the implemented
measures.