Soil erosion and sediment transport modelling using hydrological models and remote sensing techniques in Wadi Billi, Egypt

Modelling soil erosion and sediment transport are vital to assess the impact of the flash floods. However, limited research works have studied sediment transport, especially in Egypt. This paper employs the HEC-HMS lumped hydrological model to predict the sediment load due to the flood event of 9th March 2014 in Wadi Billi, Egypt. The Modified USLE model has been used to calculate the total upland erosion, while Laursen-Copeland has been used to simulate load streams’ sediment transport potential. The Normalized Difference Vegetation Index (NDVI) has been applied over Landsat 8 image captured on 20th February 2014 using ArcMap 10.5 to determine the vegetation cover based on its spectral footprint. The resulted sedigraph showed accumulation of more than five thousand tons of sediments at the Wadi’s outlet. The results are crucial to design a suitable stormwater management system to protect the downstream urban area and to use flood water for groundwater recharge.

Sediment Yield Problems in Khassa Chai Watershed Using Hydrologic Models

Upland erosion and sedimentation are one of the severe problems which faces dams as sediments occupy spaces within reservoirs storage, hence, decreasing live water storage which is the main purpose of dam’s construction. Iraq is one of the countries that will face a significant shortage of water income as a result of both the increment in water demand and of the reduction of water shares from the source countries. Thus, the existing dams in Iraq represent a strategic resource to fulfill water demands, and the sedimentation at these dams is studied to assess the quantity of sediments that reach to these reservoirs and decrease available water volume and useful life of reservoir. In the current study, Khassa Chai Dam is located in the Northeast of Iraq and its main watershed basin covers an area of about 412 km2 between Kirkuk and Al Sulaymaniyah Governorates has been selected to estimate and predict the amount of sediment yield based on 30 years of daily climate data and the events of different intensity rainstorms. Automated geospatial watershed assessment (AGWA) tool model has been used to simulate Khassa Chai Dam catchment area. This model utilizes the geographic information system (GIS) application to analyze the required data from GIS layer for digital elevation model, soil type, land use, and land cover by interference with the required climate data. The key components of AGWA model are the soil and water assessment tool model and kinematic runoff and erosion (KINEROS) model which are able to simulate complex watershed behavior to explicitly account for spatial variability of soils, rainfall distribution patterns, and vegetation. The hydrologic characteristics for Khassa Chai catchment area according to the SWAT outputs show that the most erosive sub-basins are not able to deliver the eroded material or sediments to the reservoir due to their transmission losses, percolation, and other minor obstacles. KINEROS model simulation for sediment yield is much closer to the behavior of Khassa Chai watershed in erosion and sediment transport according to the single storm events and for individually selected sub-watersheds which are closed in their location to reservoir inlet.

Appraising the cohesion of palaeoenvironmental reconstructions in north-west Spain since the mid-Holocene from a high temporal resolution multi-proxy peat record

Investigation of abrupt palaeohydrological regime change remains challenging due to site-specific noise ratios and the limitations of dating control and spatial resolution of multi-proxy records. Some of these issues are addressed through a well dated and highly resolved record from an ombrotrophic peatland in Galicia, north-west Spain. The site is in an ideal location to record marine influences and test models of past palaeoclimatic boundaries and ocean-atmosphere linkages through multi-proxy records of macrofossils, microfossils, charcoal, peat humification and loss-on-ignition data. In conjunction with many regional proxy records of terrestrial and marine origin, the data suggest spatial coherence between 5300 and ca. 3300 cal. BP and continue to link to marine responses afterwards. After ca. 2000 cal. BP, episodes of spatially consistent palaeohydrological change persist but become more short-lived, local and sporadic in north-west Iberia. These indicate an increase in the complexity of drivers of palaeoenvironmental change in recent millennia. Fire history inferred from microscopic charcoal and apparent upland erosion indicated by the loss-on-ignition profile relate to anthropogenic pressure and appear to be linked to local deforestation phases in the Xistral uplands.

Modeling soil erosion by data-driven methods using limited input variables

Soil is one of the main elements of natural resources. Accurate estimation of soil erosion is very important in optimum soil resources development and management. Analyzing soil erosion by water on cultivated lands is an important task due to the numerous problems caused by erosion. In this study, the performance of three different data-driven approaches, e.g. multilayer perceptron artificial neural network (ANN), grid partitioning (GP), and subtractive neuro-fuzzy (NF) models were evaluated for estimating soil erosion. Land use, slope, soil and upland erosion amount were used as input parameters of the applied models and the erosion values obtained by MPSIAC method were considered as the benchmark for evaluating the ANN and NF models. The applied models were assessed using the coefficient of determination (R2), the root mean square error (RMSE), the BIAS, and the variance accounted for (VAF) indices. The results showed that the subtractive NF model presented the most accurate results with the minimum RMSE value (3.775) and GP, NF and ANN models were ranked successively.

The sensitivity of landscape evolution models to spatial and temporal rainfall resolution

Climate is one of the main drivers for landscape evolution models (LEMs), yet its representation is often basic with values averaged over long time periods and frequently lumped to the same value for the whole basin. Clearly, this hides the heterogeneity of precipitation – but what impact does this averaging have on LEM outcomes? This paper examines the sensitivity of the CAESAR-Lisflood LEM to different spatial and temporal precipitation resolutions – as well as how this interacts with different size drainage basins over short and long time scales. A range of simulations were carried out varying rainfall from 0.25 hour, 5 km to 24 hour lumped resolution over three different sized basins for 30 year durations. Results showed that there was a sensitivity to temporal and spatial resolution, with the finest leading to > 100 % increases in basin sediment yields. To look at how these interactions manifested over longer time scales, several simulations were carried out to model a 1000 year period. These showed a systematic bias towards greater erosion in uplands and deposition in valley floors with the highest spatial and temporal resolution data. Further tests showed that this effect was due solely to the data resolution, not from other (e.g. orographic) factors. The implications of these findings are that past and present LEMs may be under-predicting basin sediment yields, as well upland erosion and downstream deposition - that may have significant impacts on the modelled basin profile and shape.

Quaternary chronostratigraphy and stable isotope paleoecology of Big Bone Lick, Kentucky, USA

Big Bone Lick (BBL) in northern Kentucky, USA has been a critical geologic site in the historical development of North American Quaternary vertebrate paleontology since the 1700s. Sedimentology, geoarcheology, paleontology, accelerator mass spectrometry radiocarbon and optically stimulated luminescence dating, and stable carbon and nitrogen isotope analyses were undertaken to develop a chronostratigraphy and history of erosion and deposition for the site to provide a foundation for understanding taphonomy, and species extinction and adaptation to periods of climatic and environmental change. Three geomorphic surfaces are recognized at BBL representing significant periods of floodplain aggradation since the last glacial maximum (26.5–19 ka) dating to the Oldest Dryas (Tazewell, 25–19 ka), the Older Dryas (Cary, 14–12 ka), and late Holocene (5 ka to the present). Unconformities suggest significant periods of degradation during the transitions from cold and dry to warm and moist climates from the Oldest Dryas (Tazewell) to Bølling Oscillation, from the Older Dryas (Cary) to the Allerød, and from the Younger Dryas (Valders) to the Holocene Climatic Optimum. Increased anthropogenic activities since ~ 5 ka may have increased soil upland erosion and floodplain aggradation. Stable isotopes demonstrate that the landscape has been dominated by C 3 vegetation since the last glacial maximum.

Regional soil erosion in response to land use and increased typhoon frequency and intensity, Taiwan

Reservoir sedimentation data and sediment yields from Taiwanese rivers show increased soil erosion in response to both 20th century changes in land use and a more recent increase in typhoon frequency and intensity. Decadal variations of up to 5- to 20-fold in suspended-sediment rating curves demonstrate supply-limited transport and correspond to increased sediment delivery from hillslopes due to changes in land use, regional ground shaking during the Chi-Chi earthquake, and post-2000 changes in typhoon frequency and intensity. While accelerated erosion in central Taiwan after the Chi-Chi earthquake has been documented previously, our results show that periods of increased upland erosion also occurred earlier, in response to 20th century changes in land use. Analyses of rainfall records and typhoon frequency for the period 1900–2009 further point to an island-wide increase in erosion rates corresponding to increased typhoon frequency and intensity after 1990.