Simon Dixon writes an excellent piece (admittedly published January 2014) that summarizes some of his PhD efforts in England that looked at how adding woody debris to a river in smaller catchments might effect flood conditions downstream in a more urbanized setting. The results seem to suggest that the answer is a classic ‘it depends’. On the encouraging side, it appears as though allowing floodwaters to innundate floodplain forests can help. To quote “the real take home message is the restoration of floodplain forests to entire “subcatchments” of the main catchment always decreases flood peak height after 25 years of growth, and can have dramatic effects.” Three cheers for forested floodplain restoration and connectivity!
The piece is an excellent read as are the other posts in The River Management Blog.