Incorporating geomorphic knowledge in the management of wetlands in Africa’s drylands: a rapid assessment of the Kafue Wetland
- Authors: Lidzhegu, Z , Ellery, William F N , Mantel, Sukhmani
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/157108 , vital:40087 , https://doi.org/10.1007/s13157-019-01172-9
- Description: Limited knowledge of wetland geomorphic processes often results in poor wetland management. This study aims to illustrate the importance of incorporating geomorphic knowledge of wetland origin in their management. The geomorphic origin and dynamics of the Kafue wetland were determined from the analysis of remotely sensed and geological data. The wetland is a remnant of a paleo-lake that was captured by the tributary of the middle Zambezi River. At the point of capture, resistant Muva Group metavolcanic rocks dominate narrow valleys characterised by straight channels. The resistant lithology prevents the lower Kafue River to cut into the wetland thus maintaining wetland conditions upstream. Sedimentation regime through overbank and bed deposits shaped the wetland’s structure, ecological diversity, and hydrological functioning. The operation of the Itezhi-tezhi dam has negatively impacted the wetland’s hydrological and sedimentological regime. The dam starves the system of sediment needed for promoting levee and channel bed aggradation. Regulated discharge with reduced sediment load can lead to channel incision and therefore reduce flood frequency, which may ultimately lead to wetland desiccation.
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- Date Issued: 2020
Gully erosion as a mechanism for wetland formation: an examination of two contrasting landscapes
- Authors: Pulley, Simon , Ellery, William F N , Lagesse, Juliette V , Schlegel, P Philippa , McNamara, Shaun J
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144410 , vital:38343 , DOI: 10.1002/ldr.2972
- Description: Wetlands occupy broad, gently sloping valleys characterised by net deposition. Consequently, gully incision is viewed as an agent of wetland destruction. However, little attention has been given to the role of gullies in natural wetland formation. This paper determines if gully cutting and filling cycles have led to wetland formation in both an extant eroding wetland and a semi‐arid environment that once supported wetlands. At both sites, the valley fill was investigated to identify infilled gullies, and a 14C date was obtained from the gully fill.
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- Date Issued: 2018
Classification System for Wetlands and Other Aquatic Ecosystems in South Africa:
- Authors: Ellery, William F N
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144454 , vital:38347 , https://doi.org/10.2989/10220119.2015.1025843
- Description: There have been several attempts to develop a wetland classification for South Africa, with merit in each, but a system that satisfies the needs of a wide range of professionals has been elusive. This is partly to be expected since classification systems are often user-specific. Nevertheless, and at last, the authors of Classification System for Wetlands and Other Aquatic Ecosystems in South Africa. User Manual: Inland Systems (SANBI Biodiversity Series 22) have developed a robust and comprehensive wetland classification system for South Africa that likely will have broad appeal and be widely used. Working for Wetlands, the Water Research Commission (WRC) and SANBI provided considerable support for the development of this system and there was expert input from a wide range of stakeholders.
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- Date Issued: 2015
Impact of marine inundation after a period of drought on the lakeshore vegetation of Lake St Lucia, South Africa: resilience of estuarine vegetation
- Authors: Sieben, E J J , Ellery, William F N , Dullo, B W , Grootjans, A P
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144443 , vital:38346 , DOI: 10.2989/16085914.2015.1032208
- Description: The shore of Lake St Lucia in the vicinity of Catalina Bay, in the southern part of the lake, receives freshwater input as surface and groundwater seepage from the adjacent elevated coastal plain. Vegetation, water quality and landform were recorded on the lakeshore and on the dry lakebed near one of these seepage zones. This was done along a gradient perpendicular to the lakeshore and along the lakeshore away from the fluvial source of freshwater input. A number of plant communities were found along a gradient of water salinity from the shoreline (fresh water) towards the centre of the lake, and also away from the fluvial input of water (increasingly saline). Species richness decreased with increasing salinity. The first study was conducted in 2006 after a prolonged drought associated with low lake levels and closure of the mouth, and repeated again in 2010 three years after breaching of the estuarine mouth by a tropical cyclone at sea, which caused inundation of the partly dry lakebed with sea water. The vegetation of the lakeshore after these major disturbances was remarkably similar in the two time periods, suggesting rapid recovery near freshwater seepage zones, following an influx of sea water.
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- Date Issued: 2015
Preface: proceedings of the 13th IASWS international conference
- Authors: Foster, Ian , Rowntree, Kate M , Ellery, William F N , Ogrinc, Nives , Oldham, Carolyn
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144465 , vital:38348 , DOI 10.1007/s11368-015-1276-2
- Description: Rhodes University, Grahamstown, South Africa, was the venue for the 13th IASWS International Conference, held from 15 to 18 July, 2014. This international meeting built upon and expanded developing research in South Africa on sediment processes and followed on from a successful meeting organized by Rowntree and Foster on behalf of the Southern African Association of Geomorphologists (SAAG) held in Grahamstown in 2010 and the publication of a special issue of the journal Land Degradation and Development edited by Rowntree et al. (2012).
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- Date Issued: 2015
Assessment of the long-term response to rehabilitation of two wetlands in KwaZulu-Natal, South Africa:
- Authors: Cowden, Craig , Kotze, Donovan C , Ellery, William F N , Sieben, E J J
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144431 , vital:38345 , DOI: 10.2989/16085914.2014.954518
- Description: Assessing the ecological outcomes of wetland rehabilitation activities is an important need recognised by the ‘Working for Wetlands’ programme in South Africa. An assessment of ecological response was conducted in the Killarney and Kruisfontein wetlands, KwaZulu-Natal, in 2005 prior to rehabilitation in 2006, and again in 2011 and 2012, respectively, following rehabilitation. The assessment criteria included an evaluation of changes in ecological integrity, the supply of ecosystem services, and vegetation composition. Improvements in hydrological and geomorphic integrity were recorded in both wetlands, resulting in improved ecosystem delivery.
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- Date Issued: 2014
Modelling annual evapotranspiration in a semi-arid, African savanna: functional convergence theory, MODIS LAI and the Penman–Monteith equation
- Authors: Palmer, Anthony R , Weideman, Craig I , Finca, Andiswa , Everson, Colin S , Hanan, Niall P , Ellery, William F N
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144387 , vital:38341 , DOI: 10.2989/10220119.2014.931305
- Description: Accurately measuring evapotranspiration (ET) is essential if we are to derive reasonable estimates of production and water use for semi-arid savannas. Estimates of ET are also important in defining the health of an ecosystem and the quantity of water used by the vegetation when preparing a catchment-scale water balance. We derived ET0 from an automatic weather station 30 km west of Skukuza, Kruger National Park, South Africa using the Penman– Monteith equation, and then used the MODIS LAI to inform the model of canopy phenological dynamics. This result was compared with 173 days of ET measurements from the eddy covariance (ETec) system near Skukuza in 2007 as well as from the ET recorded by a large-aperture scintillometer at the same site in 2005. The model compared favourably with both sets of measured data and, when used independently of the eddy covariance data, ETMODIS predicted an annual ET of 378 mm in 2007 for the semi-arid savanna around the Skukuza flux site.
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- Date Issued: 2014
Controls on the formation of Wakkerstroom Vlei, Mpumalanga province, South Africa:
- Authors: Joubert, R , Ellery, William F N
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144421 , vital:38344 , DOI: 10.2989/16085914.2012.762897
- Description: The present study investigated controls on the formation of Wakkerstroom Vlei, an 1 000 ha unchannelled valley-bottom wetland on the South African Highveld. Along the uppermost and lowermost reaches of the wetland, where dolerite outcrops occur along the main valley, hydrogeomorphic features typical of geological control on wetland formation are present, including a meandering river channel, oxbow lakes and greater than 3 m deep organic-poor alluvial fill. Along the main body of the wetland, however, floodplain features are absent, alluvial fill is up to 4.5 m deep and contains up to 2 m deep accumulations of peat. These characteristics deviate from the traditional model of dolerite control on wetland formation described by several other studies on Highveld wetland systems.
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- Date Issued: 2013
Epidemic transmission of intestinal schistosomiasis in the seasonal part of the Okavango Delta, Botswana:
- Authors: Appleton, C C , Ellery, William F N , Byskov, Jens , Mogkweetsinyana, S S
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144364 , vital:38339 , DOI: 10.1179/136485908X311867
- Description: A well documented epidemic of human intestinal schistosomiasis caused by Schistosoma mansoni occurred at Maun in the seasonal part of the Okavango Delta, Botswana, building from very few cases in the 1950s and early 1960s to a peak prevalence of greater than80% in the 1980s. A retrospective analysis was performed on all available records of the prevalence of S. mansoni in the Maun area and the corresponding flow records of the Thamalakane River. These revealed a statistically significant correlation between prevalence and flow, but only when a lag period was introduced. The correlation was greatest with a lag period of 5–6 years between the rise and fall of discharge and the rise and fall of transmission. Since the hydrological events in the delta follow a cyclical pattern, another epidemic around 2020 appears likely.
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- Date Issued: 2013
Halting degradation of Southern Cape peatlands in agricultural landscapes
- Authors: Job, Nancy , Ellery, William F N
- Date: 2013
- Subjects: Peatlands -- South Africa -- Southern Cape Wetland ecology -- South Africa -- Southern Cape South Africa -- Social conditions
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/50013 , vital:25951
- Description: Palmiet peatlands in the agricultural landscape are viewed by farmers as problematic. They obstruct the effective passage of water along watercourses and therefore promote localized flooding of lands and infrastructure, and they trap sediment delivered along watercourses that drowns fields and infrastructure with sedimentary deposits. These events are problematic for farmers trying to make a living off the land. Wetlands are also often viewed as wastelands that should be put to more productive use. The obvious thing to do is to bring in machinery to drain the wetlands and improve the flow of water and sediment through these wetlands.
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- Date Issued: 2013
The landscape holds answers to more questions than we have yet learned to ask : perspectives of an environmental scientist
- Authors: Ellery, William F N
- Date: 2013
- Language: English
- Type: Text
- Identifier: vital:584 , http://hdl.handle.net/10962/d1018944
- Description: [From the text] Implicit in the title of my talk is the idea that the landscape has a voice – it "holds answers". Our understanding of landscapes depends on the questions we ask about their appearance and dynamics. What I love about the voice of landscapes is its gentle nature – it whispers. It's a seductive voice, inviting one to hear secrets. I have long been curious about the intimate language of landscapes and this has stemmed from a personal connection with nature from a very early age. My interests led me into the fields of ecology and geomorphology, both of which have allowed me to unravel some of these secrets. So, in tonight’s talk there are a number of narratives that form a part of my story. The first narrative is about science. It’s about how we uncover nature’s secrets and thus create new understanding.
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- Date Issued: 2013
Peat formation in the context of the development of the Mkuze floodplain on the coastal plain of Maputaland, South Africa:
- Authors: Ellery, William F N , Grenfell, Suzanne E , Grenfell, Michael C , Humphries, M S , Barnes, K , Dahlberg, S , Kindness, A
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144354 , vital:38338 , DOI: 10.1016/j.geomorph.2011.11.009
- Description: This paper examines the geomorphological and sedimentological development of blocked-valley lakes in the Mkuze floodplain on the coastal plain of Maputaland, northern KwaZulu-Natal, South Africa. Blocked tributary valley lakes north of the floodplain become progressively shorter, broader, and less linear toward the eastern (downstream) end of the east–west oriented Mkuze floodplain. Clastic sediment forms surface sedimentary fill in tributary valleys in the west, while peat predominates tributary valley fill in the east. Two contrasting adjacent tributary valleys were examined, the more western Yengweni dominated by clastic sediment at the surface, and the more eastern Totweni with peat.
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- Date Issued: 2012
Hierarchical spatial organization and prioritization of wetlands: a conceptual model for wetland rehabilitation in South Africa
- Authors: Sieben, E J J , Ellery, William F N , Kotze, Donovan C , Rountree, M
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144399 , vital:38342 , DOI: 10.1007/s11273-011-9212-8
- Description: Wetland rehabilitation planning needs to take into account many different aspects of the wetland and its context. In South Africa, much emphasis is placed on the delivery of ecosystem services, poverty relief and skills development for those involved in labour-intensive rehabilitation measures. A framework is presented that facilitates decision-making with regards to wetland rehabilitation planning. This starts with prioritizing which wetlands need attention within a catchment. This is followed by decisions regarding which rehabilitation measures would be effective in improving certain ecosystem services based upon the aims of rehabilitation and the social context of the surrounding catchment.
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- Date Issued: 2011
The next decade of environmental science in South Africa: a horizon scan
- Authors: Shackleton, Charlie M , Scholes, Robert J , Vogel, Coleen , Wynberg, Rachel , Abrahamse, Tanya , Shackleton, Sheona E , Ellery, William F N , Gambiza, James
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/157124 , vital:40088 , https://doi.org/10.1080/03736245.2011.563064
- Description: Environmental systems are in constant flux, with feedbacks and non-linearities catalysed by natural trends and shocks as well as human actions. This poses challenges for sustainable management to promote human well-being. It requires environmental understanding and application that can accommodate such fluxes and pressures, as well as knowledge production systems and institutions that produce graduates with appropriate skills. In this article we consider these challenges in the South African context. Firstly, we summarise six significant environmental realisations from the last decade of environmental science internationally and question what they mean for the teaching of environmental science and research into environmental systems in South Africa in the near future. We then consider these lessons within the context of a horizon scan of near-term pressing environmental issues in South Africa. These include wateruse efficiency, poverty, food security, inequities in land and resource access, urbanisation, agrochemicals and water quality, promoting human well-being and economic adaptability in the face of climate change, and imbuing stronger environmental elements and stewardship into the integrated development planning processes and outcomes. Lastly, we consider the knowledge areas and skills that environmental graduates will require to be able to confront these problems in South Africa and simultaneously contribute to international debates and understandings around the complexity of environmental systems and how to manage them.
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- Date Issued: 2011
The origin and development of the Nyl River floodplain wetland, Limpopo Province, South Africa: trunk–tributary river interactions in a dryland setting
- Authors: McCarthy, Terence S , Tooth, Stephen , Jacobs, Zenobia , Rowberry, Matthew D , Thompson, Mark , Brandt, Dion , Hancox, P John , Marren, Philip M , Woodborne, Stephan , Ellery, William F N
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144321 , vital:38331 , DOI: 10.1080/03736245.2011.619324
- Description: The Nyl River floodplain wetland, one of South Africa's largest floodplain wetlands and a Ramsar site of international conservation importance, is located in an area of long-term and still active valley sediment accumulation. Creation of accommodation space for sedimentation has previously been attributed to tectonic controls, but new investigations reveal that a more likely cause is progradation of coarse-grained tributary fans across the narrow river valley downstream of the main area of floodplain wetland. Obstruction of trunk river flow and sediment transfer by these tributary fans has led to backponding and upstream gradient reduction and to accumulation of valley fills up to ∼35 m thick. Chronological control for the timing and rate of sediment accumulation is limited, but we hypothesise that a semi-arid to arid climate, characterised by asynchronous trunk–tributary activity that results in marked discontinuities in downstream water and sediment transfer, is likely to have been a key control. These interpretations are supported by other studies of dryland rivers globally and the findings add to our growing understanding of the controls on the origin and development of southern African wetlands, particularly by demonstrating how the combination of a particular physiography and a dryland climate can impart some distinctive geomorphological characteristics.
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- Date Issued: 2011
Water chemistry and effect of evapotranspiration on chemical sedimentation on the Mkuze River floodplain, South Africa:
- Authors: Humphries, M S , Kindness, A , Ellery, William F N , Hughes, J C
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144376 , vital:38340 , https://doi.org/10.1016/j.jaridenv.2011.01.013
- Description: The Mkuze Wetland System, forming part of the iSimangaliso World Heritage Site, is South Africa’s largest freshwater wetland area and is known to act as a sink for naturally occurring solutes within the landscape. The chemistry of groundwater and porewater samples, collected from two transects on the Mkuze River floodplain, was investigated to identify processes involved in the control of solute concentrations. Results show that solutes in the groundwater become increasingly concentrated under the influence of evapotranspiration, resulting in the saturation, precipitation, and accumulation of less soluble compounds.
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- Date Issued: 2011
Assessment of the environmental condition, Ecosystem service provision and sustainability of use of two wetlands in the Kamiesberg uplands:
- Authors: Kotze, Donovan C , Malan, H , Ellery, William F N , Samuals, I , Saul, L
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/157135 , vital:40089 , http://www.wrc.org.za/wp-content/uploads/mdocs/TT439-09 Conservation of Water Ecosystems.pdf
- Description: This report is one of the outputs of the Wetland Health and Importance (WHI) research programme which was funded by the Water Research Commission. The WHI represents Phase II of the National Wetlands Research Programme and was formerly known as “Wetland Health and Integrity”. Phase I, under the leadership of Professor Ellery, resulted in the “WET-Management” series of publications. Phase II, the WHI programme, was broadly aimed at assessing wetland environmental condition and socio-economic importance.
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- Date Issued: 2010
Human impacts on hydrological health and the provision of ecosystemservices: a case study of the eMthonjeni–Fairview Spring Wetland, Grahamstown, South Africa
- Authors: Sinchembe, M , Ellery, William F N
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144343 , vital:38337 , DOI: 10.2989/16085914.2010.538508
- Description: Wetland hydrological health and the provision of indirect ecosystem services in the eMthonjeni–Fairview Spring Wetland, Grahamstown, South Africa, were assessed in 2008, using the newly developed wetland assessment tools WET-Health and WET-EcoServices. Variation in health and ecosystem services were assessed over time, based on aerial photograph interpretation and the use of the score sheets in these assessment tools. Hydrological health and indirect ecosystem services of the wetland have been altered since 1949, due to human activities both in the catchment and the wetland. The most significant human intervention on the wetland's hydrological health was the result of road construction and invasion by alien plants. Water use by local residents had an unmeasurable effect on hydrological health. Wetland health is related to the provision of wetland ecosystem services, and cumulative impacts in the catchment and wetland have reduced the provision of many indirect wetland ecosystem services.
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- Date Issued: 2010
Sedimentary facies and geomorphic evolution of a blocked‐valley lake: Lake Futululu, northern Kwazulu‐Natal, South Africa
- Authors: Grenfell, Suzanne E , Ellery, William F N , Grenfell, Michael C , Ramsay, Lisa F , Flügel, Tyrel J
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126826 , vital:35928 , https://doi.10.1111/j.1365-3091.2009.01141.x
- Description: Blocked-valley lakes are formed when tributaries are impounded by the relatively rapid aggradation of a large river and its floodplain. These features are common in the landscape, and have been identified in the floodplains of the Solimo˜es-Amazon (Brazil) and Fly-Strickland Rivers (Papua New Guinea), for example, but their inaccessibility has resulted in studies being limited to remotely sensed image analysis. This paper documents the sedimentology and geomorphic evolution of a blocked-valley lake, Lake Futululu on the Mfolozi River floodplain margin, in South Africa, while also offering a context for the formation of lakes and wetlands at tributary junctions. The study combines aerial photography, elevation data from orthophotographs and field survey, and longitudinal sedimentology determined from a series of cores, which were sub-sampled for organic content and particle size analysis. Radiocarbon dating was used to gauge the rate and timing of peat accumulation. Results indicate that following the last glacial maximum, rising sea-levels caused aggradation of the Mfolozi River floodplain. By 3980 years bp, aggradation on the floodplain had impounded the Futululu drainage line, creating conditions suitable for peat formation, which has since occurred at a constant average rate of 0Æ13 cm year)1. Continued aggradation on the Mfolozi River floodplain has raised the base level of the Futululu drainage line, resulting in a series of backstepping sedimentary facies with fluvially derived sand and silt episodically prograding over lacustrine peat deposits. Blocked-valley lakes form where the trunk river has a much larger sediment load and catchment than the tributary stream. Similarly, when the relative difference in sediment loads is less, palustrine wetlands, rather than lakes, may be the result. In contrast, where tributaries drain a steep, well-connected catchment, they may impound much larger trunk rivers, creating lakes or wetlands upstream.
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- Date Issued: 2010
Geomorphology and dynamics of the Mfolozi River floodplain, KwaZulu-Natal, South Africa
- Authors: Grenfell, Suzanne E , Ellery, William F N , Grenfell, Michael C
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6633 , http://hdl.handle.net/10962/d1006827
- Description: The geomorphology and dynamics of the Mfolozi River floodplain and estuary, located in the subtropical region of northern KwaZulu-Natal, South Africa, were considered with respect to existing models of avulsion and alluvial stratigraphy. The Mfolozi River floodplain may be divided into regions based on longitudinal slope and dominant geomorphic processes. Confinement of the Mfolozi River above the floodplain has led to the development of an alluvial fan at the floodplain head, characterized by a relatively high sedimentation rate and avulsion frequency, at a gradient of 0.10%. The lower floodplain is controlled by sea level, with an average gradient of 0.05%. Between the two lies an extremely flat region with an average gradient of 0.02%, which may be controlled by faulting of the underlying bedrock. Avulsion occurrences on the Mfolozi floodplain are linked to the two main zones of aggradation, the alluvial fan at the floodplain head, and toward the river mouth in the lower floodplain. On the alluvial fan, normal flow conditions result in scour from local steepening. During infrequent, large flood events, the channel becomes overwhelmed with sediment and stream flow, and avulses. The resulting avulsion is regional, and affects the location of the channel from the floodplain head to the river mouth. Deposits resulting from such avulsions contribute significantly to the total volume of sediment stored in the floodplain, and tend to persist for long periods after the avulsion. Contrastingly, on the lower floodplain, reaching of the avulsion threshold is not necessarily linked to large flood events, but rather to long-term aggradation on the channel that decreases the existing channels gradient while increasing its elevation above the surrounding floodplain. Resultant avulsions tend to be local and do not contribute significantly to the overall volume of floodplain alluvium.
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- Date Issued: 2009