Gully Complex Research Articles

The effectiveness of alluvial gully remediation in Great Barrier Reef catchments

This study presents data from a large-scale Before After Control Impact (BACI) design field experiment that measured the sediment reduction achieved by remediating large alluvial gullies. The study was carried out on Bonnie Doon Creek on the lower Burdekin River, in Queensland Australia. Prior to remediation, the four large alluvial gully complexes (active area of ∼17ha) were conservatively estimated to be delivering 5800 ± 1500 t of fine sediment (<20 μm) per year (20 year average). The experiment demonstrated that the average remediation effectiveness across 10 different treatments was a 96%–99% reduction in fine sediment yield (or an annualised reduction of ∼5500t). High resolution lidar DEM of Difference (DoD) derived sediment yields in the unremediated gullies were found to be, on average, 58% lower than yields derived from monitored suspended sediment concentration (SSC) data, albeit with some uncertainty. These data support the notion that even high resolution (0.1m) lidar DoD yields are missing erosion driven by rainfall driven downwearing across all internal gully surfaces that is below the limit of detection (LOD) of the lidar. The results highlight that the greatest uncertainty in predicting the sediment abatement from gully remediation is associated with the determination of the baseline sediment yield of each gully. Future research effort should be focused on improving our understanding of baseline (multi-decadal) sediment yields, and monitored (annual) yields in different types of unremediated gullies. This is dependent on developing a detailed understanding of how these gullies evolve through time, and what the processes are that drive ongoing gully growth.

СЕЗОННАЯ ДИНАМИКА ХИМИЧЕСКОГО СОСТАВА ВОД ОВРАЖНО-БАЛОЧНЫХ СИСТЕМ ГОРОДСКИХ ТЕРРИТОРИЙ (НА ПРИМЕРЕ САРАТОВА)

Актуальность исследования определяется необходимостью обеспечения экологического благополучия водных объектов в зоне воздействия крупных городов. В соответствии с современными природоохранными, экологическими и градостроительными требованиями водный сток с урбанизированных территорий не должен оказывать негативного воздействия на качество водных ресурсов. Цель: определение сезонной динамики (весенний максимум и летне-осенний минимум стока) поступления загрязняющих веществ с водным стоком оврагов и балок с территории города Саратова в Волгоградское водохранилище. Методы: морфометрический анализ водосборных бассейнов овражно-балочных комплексов; картографирование притоков естественного и техногенного происхождения; опробование вод в устьевых створах перед впадением в Волгоградское водохранилище; химический анализ состава поверхностных вод по приоритетным показателям по общепринятыми методикам (суммарно 140 определений); оценка и анализ качества вод относительно нормативов для водных объектов рыбохозяйственного значения. Результаты. Выполнена характеристика функционирования городских оврагов и балок; определены особенности формирования химического состава и транспорта вод по эрозионной сети урбанизированной территории; установлен состав вод десяти крупнейших овражно-балочных комплексов по приоритетным загрязняющим веществам для Волгоградского водохранилища (нитриты, железо общее, медь, цинк, сульфаты, азот аммония, нефтепродукты); в водном стоке обнаружены концентрации загрязняющих веществ, многократно превышающие установленные нормативы для водоемов рыбохозяйственного назначения. Качество водного стока не соответствует нормативам, установленным для водных объектов рыбохозяйственного значения, к которым относится Волгоградское водохранилище как часть волжского бассейна. В сезонной динамике химического состава вод не обнаруживается однонаправленных тенденций. Из 70 сравнительных пар проб весеннего и летне-осеннего стока снижение концентраций летом выявлено в 41 случае (58,6 %), повышение – в 21 (30 %), отсутствие изменений – в 8 (11,4 %). Контроль качества стока следует вести исходя из анализа конкретных водосборных бассейнов. Учитывая, что водохранилище служит источником централизованного хозяйственно-питьевого водоснабжения и объектом рекреационной деятельности, необходима организация систем очистки поверхностного водного стока.

Channel evolution controlled by valley configuration during 70 years in a severely erosive catchment: Mangaoporo River, New Zealand

We examined the channel-evolution process in a 19.5 km course in the Mangaoporo River (catchment area: 72.6 km2) in the East Coast region of North Island, New Zealand over 70 years using aerial photographs and cross-sectional survey records. The catchment experienced expansive deforestation during the late 19th and early 20th centuries, which accelerated the growth of the gully complexes. The manner of the evolution was controlled largely by the underlying lithology that determined the valley configuration. In the upstream confined section, where hillslope and channel processes were closely coupled, continuous sediment supply from gully complexes gradually converted the channel course from a narrow single-thread to wide braided reaches, or from sediment transfer to storage zones. This change was accompanied by a decrease in unit stream power (USP). In 1939, the USP was above 200 W/m2 in most of the upstream section, while 40% of the USP values were near or below 50 W/m2 in 2012/2013. Because a narrow reach situated at the end of the storage zone limited the amount of sediment travelling further, the downstream reaches were gradually disconnected from the upstream section, and the channel forms changed more moderately than in the upstream section. This reduction in sediment travelling with distance transformed a once-braided reach at the end of the course to development of a supply-limited condition with time. The overall channel evolution was accelerated by major rainfall events, including prolonged rainfall in 1956 and Cyclone Bola in 1988, which activated gully complexes and contributed to subsequent channel widening, particularly in the upstream section. Although reforestation starting in the 1980s contributed to deactivation of gully complexes after 1988, the difficulty in controlling their total remission together with the lower USP values of the river in 2012/2013 compared to those before the previous major wet events indicate that the river has been evolving in an irreversible direction, triggered by land use changes of more than a century ago.

Badass gullies: Fluvio-mass-movement gully complexes in New Zealand's East Coast region, and potential for remediation

This paper reviews gully erosion in the East Coast region of New Zealand's North Island and conceptualises fluvio-mass-movement gully complexes as badass gully systems. Tectonic setting and lithological control, with steep slopes and a climate influenced by tropical cyclones, predispose hill country in the East Coast region to gully erosion. The clearance of indigenous forest since the late 1800s has dramatically increased catchment erosion and paved the way for development of large-scale fluvio-mass-movement gully complexes. These features are a composite of fluvial and mass movement processes. They are conceptualised as ‘badass’ by not conforming to any existing gully model and by generating disproportionate results in East Coast catchment sediment cascades. Their remediation is discussed, but their nature means that prevention is better than a cure.

Timing and causes of gully erosion in the riparian zone of the semi-arid tropical Victoria River, Australia: Management implications

Gully erosion in the seasonally wet tropics of Australia is a major source of sediment in rivers. Stabilization of gullies to reduce impacts on aquatic ecosystems and water storages is a focus for management. However, the cause of the gully erosion is poorly understood and so a critical context for soil conservation is missing. It is uncertain if they are the result of post-European cattle grazing or are they much older and related to non-human factors. The causes of riparian gully erosion along a reach of the Victoria River in the semi-arid tropics of Australia were investigated using several methods. Gully complexes were described and characterised by two major components: a Flood Drainage Channel (FDC) and upslope of this an Outer Erosion Feature (OEF) characterised by badlands set within an amphitheatre. The OEF is likely to be a major source of sediment that appears to be of recent origin. A review of historical records, combined with Optically Stimulated Luminescence (OSL) dating, showed that the FDCs were well established prior to the introduction of domestic stock. It also showed that the badlands began to develop about 90years ago; that is, about 40years after the arrival of domestic stock. In addition, an analysis of aerial photos coupled with an on-ground survey and analysis of fallout radionuclides revealed that erosion processes are still active within the gully complexes. While the FDCs are natural drainage channels, cattle grazing probably triggered the badland formation, with the expansion aided by increased rainfall in the past 40years. Therefore, the OEFs are of human origin and protection from grazing of the riparian zone should slow badland erosion and reduce sediment input to the river.

Slope–channel coupling in steepland terrain: A field-based conceptual model from the Tarndale gully and fan, Waipaoa catchment, New Zealand

Connectivity between an actively eroding gully complex and upper Waipaoa catchment via a steep, 1-km-long alluvial fan is assessed using digital elevation models (DEMs) of the Tarndale fan derived from 10 high resolution GPS surveys between 2004 and 2008. Repeat DEM analysis provides a means of assessing transfer of sediment supplied from the Tarndale gully through the fan to the Te Weraroa Stream and thus inferring connectivity between these landscape components from which a conceptual coupling model is derived. Analysis indicates the operation of two critical junction switches at the (i) gully–fan and (ii) fan–stream nexus, which contribute to considerable complexity in patterns of erosion and deposition on the fan as it responds to sediment supply or starvation from the Tarndale gully and evacuation to the Te Weraroa Stream (described in Fuller and Marden, 2010). The fan does not respond as a coherent unit. Each of six fan feeder tributaries behaves independently according to sediment supplied from six discrete source areas within the gully complex. This reflects sediment production within specific activity zones of Tarndale Gully. Mass movements, triggered by single rainstorm events and/or wet periods contingent upon sediment availability and intrinsic slope mechanics, frequently deliver sediment to the upper fan tributaries. This enhanced gully–fan coupling during storms or wetter periods promotes rapid fan aggradation, with each feeder tributary responding to its discrete source zone. Infilling may propagate down fan in response to upper fan incision once the gully–fan switch deactivates, transferring sediment as far as the Te Weraroa Stream, coupling the fan with the stream system. Floods generated in the Te Weraroa Stream may also activate the junction switch at the fan–stream nexus by trimming the lower fan, prompting up-fan incision via head-cutting in response to changed local base level. Slope–channel coupling in this environment is a function of a range of slope and channel processes responding to discrete storms and intrinsic gully dynamics. The high rates of geomorphic activity in this environment mean the Tarndale system provides a natural laboratory in which to assess key slope–channel coupling processes beyond the plot or discrete event scale.

Rapid channel response to variability in sediment supply: Cutting and filling of the Tarndale Fan, Waipaoa catchment, New Zealand

In the headwaters of the Waipaoa catchment, fluvio-mass movement gully complexes are currently significant contributors of sediment, delivery of which is buffered by fans which have developed in the small tributaries that lead from the gully complexes. Biannual channel cross-section surveys made since 1983 show seasonal aggradation / incision cycles; channels generally incise in summer and infill during the winter months. This seasonal pattern of cutting and filling is driven by variations in sediment supply from the gully complexes. In this paper, to better understand patterns and processes of sediment delivery at the top of the sediment cascade, we examine cut and fill cycles on the ~ 11 ha Tarndale Fan over a two and a half year period. Analysis of sequential DEMs compiled from survey data obtained between December 2004 and August 2007 indicates cutting and filling may involve up to 47,000 tonnes of sediment over as little as three months. During discrete severe rainstorm and/or wet weather periods, mass movements in the gully complex are enhanced and contribute large quantities of sediment to the fan, via debris flows and landslides, which infill channels. During drier periods, mass movement activity is inhibited and runoff incises the feeder channels.

Factor analysis of soil spatial variability in gully erosion area of southeastern Nigeria: A Case Study of Agulu- Nanka- Oko Area

The effect of soil characteristics on gully development and distribution has made it desirable to determine the spatial variability of its physical and chemical properties. This paper examines the spatial variability of soil properties and factors contributing to the general pattern of variability in Agulu- Nanka- Oko gully complex, Southeastern Nigerian. Five (5) gully locations and nine (9) gully profiles were selected for the investigation. Fifty one (51) soil samples were collected along the gully walls of the profiles. These soil samples were analyzed in the laboratory by standard methods (ASTM and British Standard) for soil index properties and chemical properties. The soil samples were collected at depths between 1.2 meters and 21.3 meters, where there are changes in soil types based on textural characteristics. The data were subjected to descriptive and factor analysis. The results of the statistical analyses show that there were marked contrasts in the level of variability of the soil properties. The coefficient of variation ranged from 1.24% to 47.16%. The factor analysis revealed that the variability of the soil properties is mainly due to four factors namely; chemical properties, moisture content, textural characteristics and organic carbon. Key words: Factor, analysis, spatial, variability, soil, gully

Case study of the Agacli landslide–gully complex during post-coal-mining reclamation and afforestation

The concept of sustainable development has gained wide acceptance in the fields of mining and environmental studies. Mining is a temporary activity, but its impact on the environment persists long after mine closure. The aim of this research is to investigate the effect of land-use change on the stability of the Agacli landslide, northern coastal part of the Istanbul (Turkey), spanning periods of mining, reclamation, and afforestation. Geological and geophysical surveys were performed to determine the effects of erosion on the landslide. To assess the possibility of water responsible for triggering a landslide–gully complex, the dynamic elastic parameters of the field are calculated. Field observations indicate that surface erosion and gully development have ceased in the afforested area; however, gullies in non-forested areas continue to increase in size and depth. Uncontrolled surface water and water from stock watering ponds have trigger erosion and rapid sedimentation of the landslide–gully complex, resulting in over-steepening and enhanced landslide activity on the flanks of the main slide.

Development and controlling factors of gullies and gully complexes, East Coast, New Zealand

AbstractSequential aerial photographs of a small headwater catchment in the Waiapu basin, East Coast Region, North Island, New Zealand, were interpreted to measure and analyse temporal changes in active area of gullies and gully complexes for a longer time span (1939–2003) and with higher temporal resolution compared to previous studies. We focus on the conditions leading to the development of gullies and gully complexes under pasture and forest by using topographic thresholds (slope–area relationships) of catchments for the initiation of gullies and gully complexes. In addition, the influence of two different lithologies as well as the occurrence of major rainfall events was related to gully activity.Twenty gullies and four gully complexes (occupying 62·5 ha or 12·5 per cent of the catchment area) occurred in the study catchment between 1939 and 2003. However, the majority of these were not active at all of the dates studied. Gullies developed in the sandstone‐dominated Tapuwaeroa Formation tended to attain their maximum size by 1957 with a mean catchment area of 2·1 ha. Gullies developed in mudstone of the Whangai Formation attained their maximum size in 1939 with a mean catchment area of 4·31 ha. Exceptions are gullies which developed into mass movement deposits or into an earth flow deposit as well as gullies developed under indigenous forest. Topographic threshold values for gullies under pasture and indigenous forest show that values for gullies under forest plot far above the threshold line of gullies under pasture, indicating that the topographical threshold for gully development under forest is higher compared to under pasture. A threshold value of 9·4 ha in catchment area is needed for the development of gully complexes under pasture, all located in the Whangai Formation and with the same orientation as the strike of the mudstones. Gully‐complex area and dominance of mass‐movement erosion increased with larger catchment area. A decreasing distance to the threshold line for gullies under pasture indicates a later development for gully complexes. No gully complexes developed under indigenous forest, indicating that the threshold value for gully‐complex development is higher than for gully complexes under pasture and was not reached in the study area.A model of shifting topographical threshold for gully development for a given catchment is developed which depends on land use. When a catchment has an indigenous forest cover the topographical threshold is very high. After conversion to pasture, threshold values decrease drastically. With the invasion of scrub, the threshold slowly increases and returns to a similar level to that under indigenous forest after reforestation.Development of gullies and gully complexes is a highly dynamic phenomenon, and phases of expansion and inactivity indicate that models describing only unidirectional advancing stages without periods of inactivity are not suitable. Therefore, this study adds more phases to models of gully and gully‐complex development in the East Coast Region. The threshold line for gully initiation under pasture and a value of 9·4 ha in catchment area for gully‐complex initiation permits one to predict which catchments, under similar environmental settings, develop gullies and gully complexes on a physical basis. This enables land managers to implement sustainable land‐use strategies to reduce erosion rates of gullies and gully complexes. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Impacts of land use change on patterns of sediment flux in Weraamaia catchment, New Zealand

Forest clearance between the 1890s and the early 1920s, subsequent scrub growth, and commencement of an afforestation program in 1979, modified the pattern and rate of sediment delivery to valley floors via shallow landslides and gully complexes in a steep headwater catchment (4.8 km 2) in New Zealand. Analysis of the historical record, air photograph interpretation, and field survey indicates that both erosion types occurred across the catchment in the 1938 storm, aggrading channel beds and widening the active channel zone. In contrast, a 1 in 100 year event in 1988 (Cyclone Bola) induced numerous shallow landslides, but erosion of gully complexes was largely restricted to subcatchments that retained pasture, and the geomorphic impact of this event on channels was small. The changing volume and calibre of materials delivered to the valley floor, and the distribution of gully complexes, altered patterns and rates of channel adjustment after the events, and the resulting sediment flux. Development of gully complexes maintained coupling processes with channels for periods up to 10 2 years, forming wide channels in downstream reaches. Upstream–downstream connectivity along the trunk stream was altered by the formation of a large debris fan at the confluence with a tributary subjected to gully complex erosion. In contrast, slopes subjected to shallow landslides became decoupled from channels within 10 years, accelerating channel degradation and narrowing. Effective conveyance of a large volume of fine-grained materials promoted immediate aggradation of gentle-gradient channels downstream. As gully complex areas stabilized following an increase in forest and scrub cover, channel courses became significant sediment sources. Although shallow landslide activity will continue to induce intermittent aggradation in the future, it is inferred that average sediment yield will continue to diminish to levels approaching those experienced prior to clearcutting, and the pattern of sediment flux will recover by 2030.

Significant new biostratigraphic horizons in the Qusaiba Member of the Silurian Qalibah Formation of central Saudi Arabia, and their sedimentologic expression in a sequence stratigraphic context

ABSTRACT Detailed analysis of over 1,000 subsurface Silurian palynology samples from 34 wells has allowed the development of a robust biostratigraphy based on acritarchs, chitinozoans and cryptospores for the Qusaiba Member of the Qalibah Formation, central Saudi Arabia. The new index fossils described herein augment the Arabian Plate Silurian chitinozoan zonation. The high-resolution biostratigraphic zonation consists of nine First Downhole Occurrences (FDOs) from the lower Telychian through Aeronian. In particular, three regionally recognizable palynologic horizons were identified within the lower part of the informally designated Mid-Qusaiba Sandstone (Angochitina hemeri Interval Zone), and above the FDO of Sphaerochitina solutidina. This high level of biostratigraphic resolution provides a framework for the integration of the sedimentology and calibration with global sea level curves, leading to a detailed understanding of the sequence stratigraphic evolution of this part of the Silurian in Saudi Arabia. Sedimentological core studies identify three Depositional Facies Associations (DFAs) within the Mid-Qusaiba Sandstone interval, including: (1) shelfal deposits (DFA-I) characterized by interbedded hummocky cross-stratified sandstones, graded siltstones and bioturbated mudstones; (2) turbiditic deposits (DFA-II); and (3) an association of heavily contorted and re-sedimented sandstones, siltstones and mudstones (DFA-III) that is considered representative of oversteepened slopes upon the Qusaiba shelf. Integration of the newly recognized palynostratigraphic horizons and the sedimentological data facilitates an understanding of the sequence stratigraphic evolution of the Mid-Qusaiba Sandstone interval and its immediate precursors. Thus a Maximum Flooding Surface (MFS) is identified from significant palynostratigraphic, as well as sedimentological evidence, and concurs with the MFS identified regionally with the Monograptus convolutus Graptolite Zone. Several mud-prone cyclothems downlap onto the MFS. Each of these is identified by its own palynostratigraphic marker: these mud-prone cyclothems represent the distal parts of a Highstand Systems Tract (HST). The end of the HST is marked by evidence of a major, episodic drop in relative sea level. Thus, a relationship is identified wherein successive palynostratigraphic marker horizons, newly identified in this study, are partially eroded by the introduction of sandy turbidites (DFA-II). These turbidites arise from storm-induced erosion of gully complexes in the upper submarine slopes that are present as topography upon the Qusaiba shelf. Each of the successive drops in sea level is separated from the next by a minor, subsequent sea level rise, which precludes further submarine erosion and turbidite deposition, and is instead evident in the widespread occurrence of shallow marine (shelfal) muds and sandy tempestites (DFA-I). The lowstand per se is considered to be represented by the most widespread distribution of the DFA-II turbidite deposits, and is associated with the youngest Mid-Qusaiba Sandstone marker horizon identified in this study, namely Rugosphaera agglomerata n.sp. The youngest unit of DFA-II lowstand turbidites is limited in its occurrence to the more proximal parts of the study area, and thus is considered to represent the onset of the succeeding Transgressive Systems Tract (TST). Of the biostratigraphic indices used for correlation within the Qusaiba Member, Rugosphaera agglomerata and Eupoikilofusa curvata are formally described and two additional important species, Fractoricoronula n.sp. and ?Oppilatala n.sp., are retained in open nomenclature.

Geomorphic changes in a complex gully system measured from sequential digital elevation models, and implications for management

AbstractHigh‐resolution digital elevation models (DEMs) were derived from sequential aerial photography of an active fluvio‐mass movement (gully) complex in New Zealand's North Island East Coast region, to measure geomorphic changes over approximately one year. The gully showed a complex behaviour, combining fluvial and mass movement erosion, deposition, and reworking of materials stored in an active debris fan. During the measurement period 5200 ± 1700 m3 of material were eroded from the 8·7 ha gully complex and 670 ± 180 m3 from the 0·8 ha depositional fan, giving a total of 5870 ± 1710 m3 for the entire gully complex–fan system.The results provide a high‐resolution description of gully behaviour over a short time period, and also demonstrate that mass movement (slumping and debris flows) accounted for almost 90 per cent (4660 ± 200 m3) of the sediment generated. This erosional response is described in terms of gully evolution by comparing the gully complex to other systems in the region in various stages of development. The effect of gully evolution on geomorphic coupling between the gully complex and channel system is described, and coupling is also shown to vary with the magnitude and frequency of rainfall events.From a land management perspective the success of strategies, such as tree planting, to mitigate against gully erosion depends on the stage of gully development – particularly on whether or not mass movement erosion has begun. In contrast to gully rehabilitation efforts elsewhere, basin‐wide afforestation in the early stages of gully incision is favoured over riparian planting, given that mass movement assisted by excessive groundwater pressure is the main process leading to uncontrollable gully expansion.To protect land effectively against continuing gully erosion of headwater catchments and resulting downstream aggradation, it is necessary for land managers to understand the spatial and temporal variability of gully development fully so that mitigation efforts can be targeted appropriately. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Proterozoic stratigraphy and tectonic history of the Georgetown Inlier, northeastern Queensland

The Proterozoic sequence in the central part of the Georgetown Inlier has been divided into the Etheridge, Langlovale, Croydon and Inorunie Groups. The Early to Middle Proterozoic Etheridge Group consists of shallow-water, fine-grained, clastic metasedimentary rocks, and minor basaltic lavas and related dolerite intrusions. It was deposited in a uniformly subsiding basin in a continental setting sometime between 2400 and 1570 Ma. It was first deformed at ∼ 1570 Ma (D 1) and again at ∼ 1470 Ma (D 2) by major folding events accompanied by low- to intermediate-pressure metamorphism, mainly in the greenschist and amphibolite facies, but ranging into the granulite facies in places during D 2. The grade of metamorphism increases from west to east. Extensive S-type plutonic magmatism accompanied D 2. In the west the Langlovale Group, a fluviatile to marine, pro-deltaic facies, post-dates D 1, and was deposited before D 2. It is moderately folded but not regionally metamorphosed. Post-orogenic magmatism (also S-type) is represented in the western part of the inlier by the subaerial felsic ignimbrite of the Croydon Volcanic Group and related subvolcanic granitoids. The volcanic rocks are overlaim by the fluviatile Inorunie Group which is of uncertain age. Neither the Croydon Volcanic Group nor the Inorunie Group is appreciably deformed or metamorphosed. In the eastern quarter of the inlier, a largely metavolcanic (andesitic to felsic) sequence may be an allochthonous terrain of Early Palaeozoic age, but it could be Proterozoic. Known Proterozoic rocks, thought to have been thrust over this sequence, crop out on the eastern edge of the inlier. They are the Halls Reward Metamorphics and maficultramafic rocks including the Boiler Gully Complex. Their relationship to the Etheridge Group is uncertain. Convective mantle upwelling could account for the extension of the continental crust which allowed deposition of the Etheridge Group. No rifting is apparent, and only the ‘sag phase’ of the model of Etheridge et al. may be represented. Underplating of the crust could account for the metamorphism and felsic magma generation during the Middle Proterozoic. The Etheridge Group shows characteristics of both tectonostratigraphic cycles recognized elsewhere in nothern Australia, and without better radiometric control, correlation is difficult.