The authors specifically looked at four different woodland types: catchment, cross-slope, floodplain, and riparian, to determine the relative merits of each type and their effectiveness in mitigating flood risk. They found that while there is good understanding of the processes involved and some evidence that carefully planned and managed woodland can mitigate flood risk, the published data for this evidence base is somewhat sparse. This may be either due to the long timescales needed to conduct comprehensive studies or the relative infancy of the research on NFM.