Geomorphic impact and system recovery following an extreme flood in an upland stream: Thinhope Burn, northern England, UK

Milan, David J.

doi:10.1016/j.geomorph.2011.09.017

Cited by 70 publications

(95 citation statements)

References 27 publications

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“…This event constituted the largest flood on record for the catchment and one of the largest on record in Australia in terms of specific peak discharge , overcoming entrainment thresholds for the entire grain-size population. The morphological response of the study reaches is consistent with a number of previous studies in which steep, confined channels experience decreases in morphological variability, channel widening and scour to form "U-shaped" channels (Nanson and Hean, 1985;Reinfelds and Nanson, 2004;Milan, 2012). The degree of confinement evident in the study reaches also holds implications for the nature of sediment trans-port during the 2011 flood.…”

Section: Morphological Channel Response To the January 2011 Flood Andsupporting

confidence: 87%

“…3) indicate that these empirical equations underestimate the effectiveness of catastrophic floods in such settings. The entrainment of unusually large clasts and comparatively voluminous bedload deposits during large floods is not unique, having been observed in other headwater drainage basins (Milan, 2012) and may be a function of non-Newtonian flow conditions associated with high concentrations of debris or simply be a function of scour on the downstream side. The study reaches of the upper Lockyer possess significantly lower gradients than channels typically associated with the hyper-concentrated flows (Costa, 1974).…”

Section: Morphological Channel Response To the January 2011 Flood Andmentioning

confidence: 96%

“…Bedrock channels in small catchments typically have highly variable flow regimes and resistant boundary conditions. Lowfrequency, high-discharge floods are the "geomorphically effective" floods, as larger flows are required to mobilise sediment and propagate bedrock erosion and incision (Wolman and Miller, 1960;Costa and O'Connor, 1995;Baker and Kale, 1998;Milan, 2012). Due to the fact that individual settings exhibit different characteristics in terms of boundary resistance and the frequency of effective processes and rates of recuperative processes, the magnitude of a discharge is only one factor in determining the extent of changes caused by an event (Costa, 1974).…”

Section: Response Of Bedrock Channels To Disturbancementioning

confidence: 99%

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Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood

et al. 2015

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Abstract. The role of extreme events in shaping the Earth's surface is one that has held the interests of Earth scientists for centuries. A catastrophic flood in a tectonically quiescent setting in eastern Australia in 2011 provides valuable insight into how semi-alluvial channels respond to such events. Field survey data (3 reaches) and desktop analyses (10 reaches) with catchment areas ranging from 0.5 to 168 km 2 show that the predicted discharge for the 2011 event ranged from 415 to 933 m 3 s −1 , with unit stream power estimates of up to 1077 W m −2 . Estimated entrainment relationships predict the mobility of the entire grain-size population, and field data suggest the localised mobility of boulders up to 4.8 m in diameter. Analysis of repeat lidar data demonstrates that all reaches (field and desktop) were areas of net degradation via extensive scouring of coarse-grained alluvium with a strong positive relationship between catchment area and normalised erosion (R 2 = 0.72-0.74). The extensive scouring in the 2011 flood decreased thalweg variance significantly removing previous step pools and other coarse-grained in-channel units, forming lengths of plane-bed (cobble) reach morphology. This was also accompanied by the exposure of planar bedrock surfaces, marginal bedrock straths and bedrock steps. Post-flood field data indicate a slight increase in thalweg variance as a result of the smaller 2013 flood rebuilding the alluvial overprint with pool-riffle formation. However, the current form and distribution of channel morphological units does not conform to previous classifications of bedrock or headwater river systems. This variation in postflood form indicates that in semi-alluvial systems extreme events are significant for re-setting the morphology of in-channel units and for exposing the underlying lithology to ongoing erosion.

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Section: Morphological Channel Response To the January 2011 Flood Andsupporting

confidence: 87%

Section: Morphological Channel Response To the January 2011 Flood Andmentioning

confidence: 96%

Section: Response Of Bedrock Channels To Disturbancementioning

confidence: 99%

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Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood

et al. 2015

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“…Whilst these simplifications are perfectly justified given the scope and context of many of the reported modelling studies (e.g. when modelling millennial time scales), under climate change the changing risk of large flood events may have a profound effect on river systems and their geomorphology (Mayes et al, 2006;Milan, 2012) and thus a more sophisticated downscaling approach that accounts for changes to both the variability and extremes of rainfall is needed.…”

Section: T J Coulthard Et Al: Using the Ukcp09 Probabilistic Scenamentioning

confidence: 99%

Using the UKCP09 probabilistic scenarios to model the amplified impact of climate change on drainage basin sediment yield

Coulthard

Ramírez

Fowler

et al. 2012

Hydrol. Earth Syst. Sci.

103

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Abstract. Precipitation intensities and the frequency of extreme events are projected to increase under climate change. These rainfall changes will lead to increases in the magnitude and frequency of flood events that will, in turn, affect patterns of erosion and deposition within river basins. These geomorphic changes to river systems may affect flood conveyance, infrastructure resilience, channel pattern, and habitat status as well as sediment, nutrient and carbon fluxes. Previous research modelling climatic influences on geomorphic changes has been limited by how climate variability and change are represented by downscaling from global or regional climate models. Furthermore, the non-linearity of the climatic, hydrological and geomorphic systems involved generate large uncertainties at each stage of the modelling process creating an uncertainty "cascade".This study integrates state-of-the-art approaches from the climate change and geomorphic communities to address these issues in a probabilistic modelling study of the Swale catchment, UK. The UKCP09 weather generator is used to simulate hourly rainfall for the baseline and climate change scenarios up to 2099, and used to drive the CAESAR landscape evolution model to simulate geomorphic change. Results show that winter rainfall is projected to increase, with larger increases at the extremes. The impact of the increasing rainfall is amplified through the translation into catchment runoff and in turn sediment yield with a 100 % increase in catchment mean sediment yield predicted between the baseline and the 2070-2099 High emissions scenario. Significant increases are shown between all climate change scenarios and baseline values. Analysis of extreme events also shows the amplification effect from rainfall to sediment delivery with even greater amplification associated with higher return period events. Furthermore, for the 2070-2099 High emissions scenario, sediment discharges from 50-yr return period events are predicted to be 5 times larger than baseline values.

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“…Also bedforms play a significant role on friction factor and sediment transport in rivers (Garcia, 2008;Julien, 2010). In the past half-century, a lot of attempts have been done to relate bedform and flow characteristics in alluvial channels (e.g., Carling, 1999;Carling et al, 2005;Formann et al, 2007;Keylock et al, 2014;Liedermann et al, 2014;MacVicar and Rennie, 2012;Milan, 2012;Singh et al, 2012;van der Mark et al, 2008). From the published research work including above-mentioned literature, some issues do need further investigation including the aspect ratio (the ratio of channel width W, to flow depth h).…”

Section: Introductionmentioning

confidence: 99%

Bedform characteristics in a gravel-bed river

Afzalimehr

Maddahi

Sui

2017

Journal of Hydrology and Hydromechanics

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Estimation of hydraulic and geometric parameters of a gravel-bed river such as dimensions of bedforms is very difficult task, although they play a fundamental role in river engineering projects. One of the methods to get essential information regarding the bedform characteristics is to find the relations between the flow parameters and bedform dimensions. We conducted this field study in the Babolroud River in northern Iran to investigate the application of double averaged method in unspecific gravel bedforms to evaluate friction factor. Using data collected from several river reaches with total length of 356 m of a gravel-bed river, the relationship between bedform geometry (height and the length of bedforms) and flow parameters including shear velocity, transport stage parameter with friction factor is investigated. Different methods for estimating bedforms dimensions are examined to assess the ability of predicting bedform parameters (length and height) in a gravel-bed river. Using bedform parameters, the contribution of particle and form friction is estimated. Results confirm the application of the double averaged method and existing bedform parameters for unspecific bedforms. There exists a similar trend between aspect ratio and friction factor in gravel bedforms.

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Geomorphic impact and system recovery following an extreme flood in an upland stream: Thinhope Burn, northern England, UK

Cited by 70 publications

References 27 publications

Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood

Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood

Using the UKCP09 probabilistic scenarios to model the amplified impact of climate change on drainage basin sediment yield

Bedform characteristics in a gravel-bed river

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