Dynamics of large wood during a flash flood in two mountain catchments
Understanding and modelling the dynamics of large wood (LW) in rivers during flood events has spurred a great deal of research in recent years. However, few studies have documented the effect of high-magnitude flash floods on LW recruitment, transport and deposition. On 25 October 2011, the Magra ri...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-08-01
|
| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | http://www.nat-hazards-earth-syst-sci.net/15/1741/2015/nhess-15-1741-2015.pdf |
| _version_ | 1818588429979484160 |
|---|---|
| author | A. Lucía F. Comiti M. Borga M. Cavalli L. Marchi |
| author_facet | A. Lucía F. Comiti M. Borga M. Cavalli L. Marchi |
| author_sort | A. Lucía |
| collection | DOAJ |
| description | Understanding and modelling the dynamics of large wood (LW) in rivers during
flood events has spurred a great deal of research in recent years. However,
few studies have documented the effect of high-magnitude flash floods on LW
recruitment, transport and deposition. On 25 October 2011, the Magra river
basin (north-western Italy) was hit by an intense rainstorm, with hourly
rainfall rates up to 130 mm h<sup>−1</sup> and event rain accumulations up to
540 mm in 8 h. Such large rainfall intensities originated flash floods in
the main river channels and in several tributaries, causing severe damages
and loss of lives. Numerous bridges were partly or fully clogged by LW jams.
A post-flood survey was carried out along the channels of two catchments that
were severely and similarly affected by this event, the Gravegnola
(34.3 km<sup>2</sup>) and Pogliaschina (25.1 km<sup>2</sup>). The analysis highlighted
a very relevant channel widening in many channel reaches, which was more
marked in the Gravegnola basin due to highly erodible material forming the
slopes adjacent to the fluvial corridor. Large wood recruitment rates were very
high, up to 1270 m<sup>3</sup> km<sup>−1</sup>, and most of it (70–80 %) was
eroded from the floodplains as a consequence of channel-widening processes,
while the rest came from hillslopes processes. Overall, drainage area and
channel slope are the most relevant controlling variables in explaining the
reach-scale variability of LW recruitment, whereas LW deposition appears to
be more complex, as correlation analysis did not evidence any statistically
significant relationship with the tested controlling variables. Indeed,
in-channel LW displacement during the flood has been mostly limited by the
presence of bridges, given the relatively large width attained by channels
after the event. |
| first_indexed | 2024-12-16T09:24:37Z |
| format | Article |
| id | doaj.art-cd441475aa28438f85c58c92207ecf84 |
| institution | Directory Open Access Journal |
| issn | 1561-8633 1684-9981 |
| language | English |
| last_indexed | 2024-12-16T09:24:37Z |
| publishDate | 2015-08-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Natural Hazards and Earth System Sciences |
| spelling | doaj.art-cd441475aa28438f85c58c92207ecf842022-12-21T22:36:40ZengCopernicus PublicationsNatural Hazards and Earth System Sciences1561-86331684-99812015-08-011581741175510.5194/nhess-15-1741-2015Dynamics of large wood during a flash flood in two mountain catchmentsA. Lucía0F. Comiti1M. Borga2M. Cavalli3L. Marchi4Faculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, ItalyFaculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, ItalyDepartment of Land and Agroforest Environments, University of Padova, Legnaro, ItalyCNR IRPI, Padova, ItalyCNR IRPI, Padova, ItalyUnderstanding and modelling the dynamics of large wood (LW) in rivers during flood events has spurred a great deal of research in recent years. However, few studies have documented the effect of high-magnitude flash floods on LW recruitment, transport and deposition. On 25 October 2011, the Magra river basin (north-western Italy) was hit by an intense rainstorm, with hourly rainfall rates up to 130 mm h<sup>−1</sup> and event rain accumulations up to 540 mm in 8 h. Such large rainfall intensities originated flash floods in the main river channels and in several tributaries, causing severe damages and loss of lives. Numerous bridges were partly or fully clogged by LW jams. A post-flood survey was carried out along the channels of two catchments that were severely and similarly affected by this event, the Gravegnola (34.3 km<sup>2</sup>) and Pogliaschina (25.1 km<sup>2</sup>). The analysis highlighted a very relevant channel widening in many channel reaches, which was more marked in the Gravegnola basin due to highly erodible material forming the slopes adjacent to the fluvial corridor. Large wood recruitment rates were very high, up to 1270 m<sup>3</sup> km<sup>−1</sup>, and most of it (70–80 %) was eroded from the floodplains as a consequence of channel-widening processes, while the rest came from hillslopes processes. Overall, drainage area and channel slope are the most relevant controlling variables in explaining the reach-scale variability of LW recruitment, whereas LW deposition appears to be more complex, as correlation analysis did not evidence any statistically significant relationship with the tested controlling variables. Indeed, in-channel LW displacement during the flood has been mostly limited by the presence of bridges, given the relatively large width attained by channels after the event.http://www.nat-hazards-earth-syst-sci.net/15/1741/2015/nhess-15-1741-2015.pdf |
| spellingShingle | A. Lucía F. Comiti M. Borga M. Cavalli L. Marchi Dynamics of large wood during a flash flood in two mountain catchments Natural Hazards and Earth System Sciences |
| title | Dynamics of large wood during a flash flood in two mountain catchments |
| title_full | Dynamics of large wood during a flash flood in two mountain catchments |
| title_fullStr | Dynamics of large wood during a flash flood in two mountain catchments |
| title_full_unstemmed | Dynamics of large wood during a flash flood in two mountain catchments |
| title_short | Dynamics of large wood during a flash flood in two mountain catchments |
| title_sort | dynamics of large wood during a flash flood in two mountain catchments |
| url | http://www.nat-hazards-earth-syst-sci.net/15/1741/2015/nhess-15-1741-2015.pdf |
| work_keys_str_mv | AT alucia dynamicsoflargewoodduringaflashfloodintwomountaincatchments AT fcomiti dynamicsoflargewoodduringaflashfloodintwomountaincatchments AT mborga dynamicsoflargewoodduringaflashfloodintwomountaincatchments AT mcavalli dynamicsoflargewoodduringaflashfloodintwomountaincatchments AT lmarchi dynamicsoflargewoodduringaflashfloodintwomountaincatchments |