Channel adjustments and vegetation cover dynamics in a large gravel bed river over the last 200 years

Comiti, Francesco; Canal, Mowry; Surian, Nicola; Mao, Luca; Picco, Lorenzo; Lenzi, Mario Aristide

doi:10.1016/j.geomorph.2010.09.011

Cited by 184 publications

(214 citation statements)

References 45 publications

(72 reference statements)

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“…Bed degradation and the development of bed armouring and channel narrowing have been detected in several tributaries in the Rhône basin Piégay, 2001, 2002), and in Pyrenean rivers (Beguería et al, 2006), whereas some Italian rivers underwent a change from braiding toward single-thread channels (Surian et al, 2010;Comiti et al, 2011), with extensive streambed degradation threatening the stability of infrastructure, as has occurred in the Arno River (Billi and Rinaldi, 1997) Mediterranean deltas have also been destabilized by the construction of large reservoirs, which behave as sediment traps, reducing sediment transfer towards the sea (Tena et al, 2011).…”

Section: Land-use Intensification and Extensificationmentioning

confidence: 99%

Erosion in Mediterranean landscapes: Changes and future challenges

et al. 2013

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Intense erosion processes are widespread in the Mediterranean region, and include sheet wash erosion, rilling, gullying, shallow landsliding, and the development of large and active badlands in both subhumid and semi-arid areas. This review analyses the main environmental and human features related to soil erosion processes, and the main factors that explain the extreme variability of factors influencing soil erosion, particularly recent land use changes. The importance of erosion in the Mediterranean is related to the long history of human activity in a region characterized by low levels of annual precipitation, the occurrence of intense rainstorms and long-lasting droughts, high evapotranspiration, the presence of steep slopes and the occurrence of recent tectonic activity, together with the recurrent use of fire, overgrazing and farming. These factors have resulted in a complex landscape in which intensification and abandonment, wealth and poverty can co-exist. The changing conditions of national and international markets and the evolution of population pressure are now the main drivers explaining land use changes, including farmland abandonment in mountain areas, the expansion of some subsidized crops to marginal lands, and the development of new terraces affected by landslides and intense soil erosion during extreme rainstorm events. The occurrence of human-related forest fires affecting thousands of hectares each year is an increasing problem in both the northern and southern areas of the Mediterranean basin. Here, we highlight the rise of new scientific challenges in controlling the negative consequences of soil erosion in the Mediterranean region: (i) to reduce the effects and extent of forest fires, and restructure the spatial organization of abandoned landscapes; (ii) to provide guidance for making EU agricultural policy more adapted to the complexity and fragility of Mediterranean environments; (iii) to develop field methods and models to improve the identification of runoff and sediment contributing areas; (iv) to contribute to the conservation of landscapes (i.e. bench-terraced fields) having high cultural and productivity values; (v) to improve knowledge of the hydrological and geomorphological functioning of badlands, with the aim of reducing sediment yield and accessibility; (vi) to better understand the effect of climate change on soil erosion in the Mediterranean region; and (vii) to improve quantitative information on long-term soil erosion. COVER LETTER

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Section: Land-use Intensification and Extensificationmentioning

confidence: 99%

Erosion in Mediterranean landscapes: Changes and future challenges

et al. 2013

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“…Abernethy andRutherfurd, 2000, Pollen Bankhead andSimon, 2010), particularly where the bank height is not greater than the predominant rooting depth. Even in incised gravel bed rivers, where bank undercutting is not significantly reduced by tree root systems, vegetation still exerts a strong morphological control within the channel by stabilizing sediment bars (Comiti et al, 2011).…”

Section: Interactions Between Riparian Vegetation Wood and River Chamentioning

confidence: 99%

Physical modelling of the combined effect of vegetation and wood on river morphology

et al. 2015

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The research reported in this paper employs flume experiments to investigate the potential effects of living vegetation and large wood on river morphology, specifically aiming to explore how different wood input and vegetation scenarios impact channel patterns and dynamics.We used a mobile bed laboratory flume, divided into three parallel channels (1.7 m wide, 10 m long) filled with uniform sand to reproduce braided networks subject to a series of cycles of flooding, wood input, and vegetation growth. Temporal evolution of river configuration (in terms of the braiding index), vegetation establishment and erosion, and wood deposition amount and pattern was recorded in a series of vertical images. The experiments reproduced many forms and processes that have been observed in the field, from scattered logs in unvegetated, dynamic braided channels, to large wood jams associated with river bars and bends in vegetated, stable, single thread rivers. Results showed that the inclusion of vegetation in the experiments changes wood dynamics, in terms of both the quantity that is stored and the depositional patterns that develop. Vegetated banks increased channel stability, reducing lateral erosion and the number of active channels. This promoted the formation of stable wood jams, where logs accumulated continuously at the same locations during subsequent floods, reinforcing their effect on river morphology. The feasibility of studying these processes in a controlled environment opens new possibilities for disentangling the complex linkages in the biogeomorphological evolution of the fluvial system and thus for promoting improved scientific understanding.

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“…Techniques of remote sensing have been widely applied to river change studies. Based on aerial photograph analysis, researchers can join traditional maps to analyze long-term island changes and channel expansion/narrowing [7], or combine field surveys to evaluate the impact of changing sediment flux on braided river evolution [8] and also to observe sediment pulses after bend cutoffs in wandering rivers [9]. Moreover, remote sensing from satellites can capture recurrent images and have multi-spectral sensors, becoming a powerful tool to monitor changes on the earth's surface over a large area.…”

Section: Introductionmentioning

confidence: 99%

Channel Planform Dynamics Monitoring and Channel Stability Assessment in Two Sediment-Rich Rivers in Taiwan

Chen

Yang

et al. 2017

Water

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Recurrent flood events induced by typhoons are powerful agents to modify channel morphology in Taiwan's rivers. Frequent channel migrations reflect highly sensitive valley floors and increase the risk to infrastructure and residents along rivers. Therefore, monitoring channel planforms is essential for analyzing channel stability as well as improving river management. This study analyzed annual channel changes along two sediment-rich rivers, the Zhuoshui River and the Gaoping River, from 2008 to 2015 based on satellite images of FORMOSAT-2. Channel areas were digitized from mid-catchment to river mouth (~90 km). Channel stability for reaches was assessed through analyzing the changes of river indices including braid index, active channel width, and channel activity. In general, the valley width plays a key role in braided degree, active channel width, and channel activity. These indices increase as the valley width expands whereas the braid index decreases slightly close to the river mouth due to the change of river types. This downstream pattern in the Zhuoshui River was interrupted by hydraulic construction which resulted in limited changes downstream from the weir, due to the lack of water and sediment supply. A 200-year flood, Typhoon Morakot in 2009, induced significant changes in the two rivers. The highly active landscape in Taiwan results in very sensitive channels compared to other regions. An integrated Sensitivity Index was proposed for identifying unstable reaches, which could be a useful reference for river authorities when making priorities in river regulation strategy. This study shows that satellite image monitoring coupled with river indices analysis could be an effective tool to evaluate spatial and temporal changes in channel stability in highly dynamic river systems.

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Channel adjustments and vegetation cover dynamics in a large gravel bed river over the last 200 years

Cited by 184 publications

References 45 publications

Erosion in Mediterranean landscapes: Changes and future challenges

Erosion in Mediterranean landscapes: Changes and future challenges

Physical modelling of the combined effect of vegetation and wood on river morphology

Channel Planform Dynamics Monitoring and Channel Stability Assessment in Two Sediment-Rich Rivers in Taiwan

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