Effects of DEM resolutions on LS and hillslope erosion estimation in a burnt landscape

Soil Research ◽  
2019 ◽  
Vol 57 (7) ◽  
pp. 797 ◽  
Author(s):  
Linxin Shan ◽  
Xihua Yang ◽  
Qinggaozi Zhu
Keyword(s):  
Sampling Method ◽  
Sampling Methods ◽  
Slope Angle ◽  
Slope Length ◽  
Dem Resolution ◽  
South Wales ◽  
Digital Elevation ◽  
Erosion Models ◽  
Optimal Resolution ◽  
Erosion Modelling

The combined slope length and slope steepness factor (LS) is crucial in soil erosion models such as the revised universal soil loss equation (RUSLE), and is often calculated from digital elevation models (DEMs). With high-resolution DEMs becoming increasingly available in recent years, we face considerable challenges in selecting the optimal DEM for erosion modelling. In this paper, we present a case study on LS factor computation using various DEMs at resolutions ranging from 1 to 90 m over a burnt national park in New South Wales, Australia, aiming to assess the effects of DEM resolution on LS and hillslope erosion estimation. The LS was calculated based on RUSLE specifications and incorporated a variable cutoff slope angle that improves the detection of the beginning and the end of each slope length. Results show the trend of an increase in the estimated LS value as the DEM resolution became coarser. We consider 5–10-m DEMs to have optimal resolution because the LS values calculated at this range were closer to the LS values measured at the 12 soil plots over the study area. We also assessed different sampling methods for LS value extraction and statistical analysis. The sampling method based on contributing area was more representative compared with point-based and buffer sampling methods. Findings from this study will be useful for choosing the optimal DEM resolution and sampling method in hillslope erosion modelling.

scholarly journals Possibilities of including surface runoff barriers in the slope-length factor calculation in the GIS environment and its integration in the user-friendly LS-RUSLE tool

2020 ◽  
Vol 15 (No. 4) ◽  
pp. 246-257
Author(s):  
Jiří Brychta ◽  
Martina Brychtová
Keyword(s):  
Surface Runoff ◽  
Flow Direction ◽  
Slope Angle ◽  
Pixel Resolution ◽  
Slope Length ◽  
Slope Length Factor ◽  
Ephemeral Gullies ◽  
Erosion Modelling ◽  
Gis Environment ◽  
User Friendly

The effect of the morphology is key aspect of erosion modelling. In Universal Soil Loss Equation (USLE) type methods, this effect is expressed by the topographic factor (LS). The LS calculation in GIS is performed by a unit contributing area (UCA) method and can mainly be influenced by the pixel resolution, by the flow direction algorithm and by the inclusion of a hydrologically closed unit (HCU) principle, the cutoff slope angle (CSA) principle and the ephemeral gullies extraction (EG) principle. This research presents a new LS-RUSLE tool created with the inclusion of these principles in the automatic user-friendly GIS tool. The HCU principle using a specific surface runoff interruption algorithm, based on pixels with NoData values at the interruption points (pixels), appears to be key. With this procedure, the occurrence of overestimation results by flow conversion was rapidly reduced. Additionally, the reduction of extreme L and LS values calculated in the GIS environment was reached by the application of the CSA and EG principles. The results of the LS-RUSLE model show the prospective use of this tool in practice.

Digital mapping of RUSLE slope length and steepness factor across New South Wales, Australia

Soil Research ◽  
2015 ◽  
Vol 53 (2) ◽  
pp. 216 ◽  
Author(s):  
Xihua Yang
Keyword(s):  
Land Use Planning ◽  
Soil Loss ◽  
Overland Flow ◽  
New South ◽  
New South Wales ◽  
Slope Angle ◽  
Universal Soil Loss Equation ◽  
Slope Length ◽  
South Wales ◽  
Soil Loss Equation

The Universal Soil Loss Equation (USLE) and its main derivate, the Revised Universal Soil Loss Equation (RUSLE), are widely used in estimating hillslope erosion. The effects of topography on hillslope erosion are estimated through the product of slope length (L) and slope steepness (S) subfactors, or LS factor, which often contains the highest detail and plays the most influential role in RUSLE. However, current LS maps in New South Wales (NSW) are either incomplete (e.g. point-based) or too coarse (e.g. 250 m), limiting RUSLE-based applications. The aim of this study was to develop automated procedures in a geographic information system (GIS) to estimate and map the LS factor across NSW. The method was based on RUSLE specifications and it incorporated a variable cutoff slope angle, which improves the detection of the beginning and end of each slope length. An overland-flow length algorithm for L subfactor calculation was applied through iterative slope-length cumulation and maximum downhill slope angle. Automated GIS scripts have been developed for LS factor calculation so that the only required input data are digital elevation models (DEMs). Hydrologically corrected DEMs were used for LS factor calculation on a catchment basis, then merged to form a seamless LS-factor digital map for NSW with a spatial resolution ~30 m (or 1 s). The modelled LS values were compared with the reference LS values, and the coefficient of efficiency reached 0.97. The high-resolution digital LS map produced is now being used along with other RUSLE factors in hillslope erosion modelling and land-use planning at local and regional scales across NSW.

scholarly journals The use of LIDAR as a data source for digital elevation models – a study of the relationship between the accuracy of digital elevation models and topographical attributes in northern peatlands

2011 ◽  
Vol 8 (3) ◽  
pp. 5497-5522 ◽  
Author(s):  
A. Hasan ◽  
P. Pilesjö ◽  
A. Persson
Keyword(s):  
High Resolution ◽  
Interpolation Method ◽  
Digital Elevation Models ◽  
Drainage Area ◽  
Absolute Deviation ◽  
Weighting Method ◽  
Dem Resolution ◽  
Coarse Resolution ◽  
Digital Elevation ◽  
Topographical Attributes

Abstract. It is important to study the factors affecting estimates of wetness since wetness is crucial in climate change studies. The availability of digital elevation models (DEMs) generated with high resolution data is increasing, and their use is expanding. LIDAR earth elevation data have been used to create several DEMs with different resolutions, using various interpolation parameters, in order to compare the models with collected surface data. The aim is to study the accuracy of DEMs in relation to topographical attributes such as slope and drainage area, which are normally used to estimate the wetness in terms of topographic wetness indices. Evaluation points were chosen from the high-resolution LIDAR dataset at a maximum distance of 10 mm from the cell center for each DEM resolution studied, 0.5, 1, 5, 10, 30 and 90 m. The interpolation method used was inverse distance weighting method with four search radii: 1, 2, 5 and 10 m. The DEM was evaluated using a quantile-quantile test and the normalized median absolute deviation. The accuracy of the estimated elevation for different slopes was tested using the DEM with 0.5 m resolution. Drainage areas were investigated at three resolutions, with coinciding evaluation points. The ability of the model to generate the drainage area at each resolution was obtained by pairwise comparison of three data subsets. The results show that the accuracy of the elevations obtained with the DEM model are the same for different resolutions, but vary with search radius. The accuracy of the values (NMAD of errors) varies from 29.7 mm to 88.9 mm, being higher for flatter areas. It was also found that the accuracy of the drainage area is highly dependent on DEM resolution. Coarse resolution yielded larger estimates of the drainage area but lower slope values. This may lead to overestimation of wetness values when using a coarse resolution DEM.

Non-Probabilistic Sampling in Quantitative Clinical Research

2022 ◽  
Vol 7 (1) ◽  
pp. 0-0
Keyword(s):  
Best Practices ◽  
Quantitative Research ◽  
Sampling Method ◽  
Sampling Methods ◽  
Early Career ◽  
Probability Sampling ◽  
Probabilistic Sampling ◽  
Quantitative Studies ◽  
Health Studies ◽  
Probabilistic Sample

Quantitative researchers need a probabilistic sample to generalise their findings, but research constraints often compel them to use non-probabilistic samples. The use of non-probability sampling methods in quantitative studies has therefore become a norm. Interestingly, even studies published in top-quality journals compromise best practices that the use of non-probabilistic samples requires. Based on a thorough review of relevant studies, we developed a typology of non-probability sampling methods used in quantitative health studies. An attempt was made to discuss the limit of inference under each type of non-probability sampling method. Non-probability sampling in quantitative research was also delineated as a way to maximise response rate. This study is expected to guide students and early career epidemiologists to understand how to apply non-probabilistic sampling methods in quantitative approaches and plausibly document or report their chosen methods.

Digital instruments for reporting of gastrointestinal symptoms in clinical trials: comparison of end-of-day diaries versus experience sampling method (Preprint)

2021 ◽  
Author(s):  
Abraham B. Beckers ◽  
Johanna T.W. Snijkers ◽  
Zsa Zsa R.M. Weerts ◽  
Lisa Vork ◽  
Tim Klaassen ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Randomized Controlled Trial ◽  
Irritable Bowel Syndrome ◽  
Sampling Method ◽  
Sampling Methods ◽  
Controlled Trial ◽  
Smartphone Application ◽  
Randomized Controlled ◽  
Pre Treatment ◽  
Irritable Bowel

BACKGROUND Questionnaires are necessary tools for assessing symptoms of disorders of the brain-gut interaction in clinical trials. We previously reported on the excellent compliance to a smartphone app used as symptom diary in a randomized clinical trial in irritable bowel syndrome (IBS). Other sampling methods, such as the experience sampling method (ESM), are better equipped to measure symptom variability over time, provide useful information regarding possible symptom triggers and are free of ecological and recall bias. The high frequency of measurements, however, could limit the feasibility of ESM in clinical trials. OBJECTIVE This study aimed to compare compliance rates of a smartphone-based end-of-day diary and ESM for symptom assessment in irritable bowel syndrome and functional dyspepsia (FD). METHODS Data from four studies were included. Patients with IBS participated in a randomized controlled trial, which involved a smartphone end-of-day diary of 2+8 weeks (pre-treatment + treatment period), and an observational study, during which patients completed ESM assessments using a smartphone application for one week. Patients with FD participated in a randomized controlled trial, which involved a smartphone end-of-day diary of 2+12 weeks (pre-treatment + treatment period), and an observational study, during which patients completed ESM assessments using a smartphone application for one week. Compliance rates were compared between these two symptom sampling methods. RESULTS Twenty-five patients with IBS and fifteen patients with FD were included. Overall compliance rates for the end-of-day diaries were significantly higher than for ESM (IBS: 92.7% versus 69.8%, FD: 90.1% versus 61.4%, respectively). CONCLUSIONS We here demonstrate excellent compliance rates for smartphone application-based end-of-day diaries as used in two separate clinical trials. Overall compliance rates for ESM were significantly lower, rendering it more suitable for intermittent sampling periods rather than continuously during longer clinical trials.

Sampling Methods and Frozen Storage of Samples for Detection of Campylobacter jejuni on Freshly Processed Broiler Carcasses

1983 ◽  
Vol 46 (6) ◽  
pp. 510-513 ◽  
Author(s):  
L. C. BLANKENSHIP ◽  
S. E. CRAVEN ◽  
J. Y. CHIU ◽  
G. W. KRUMM
Keyword(s):  
Campylobacter Jejuni ◽  
Sampling Method ◽  
Sampling Methods ◽  
Frozen Storage ◽  
Test Tube ◽  
Tissue Samples ◽  
Defibrinated Sheep Blood ◽  
Cryoprotective Agents ◽  
Plastic Bags ◽  
Sampling Locations

Swab, rinse and excision sampling methods are commonly used for detection of microorganisms on poultry carcasses. Swabbing has been the most frequently reported sampling method for Campylobacter jejuni on poultry. We evaluated the three methods for C. jejuni detection on freshly processed poultry in the following ways: (a) the interior and exterior surfaces of half of a carcass were each thoroughly rubbed with separate swabs which were combined in a test tube containing 2 ml of appropriate medium; (b) 25 g of skin and tissue samples from neck and abdominal opening cut areas were deposited in a stomacher bag with 5 ml of brucella broth (BB) and stomached for 2 min; and (c) half carcasses were shaken for 1 min with 100 ml BB in plastic bags. One drop of each sample was streaked for isolation on brucella agar containing 10% defibrinated sheep blood and Skirrow antibiotics. Isolates were identified by microscopy and appropriate cultural tests. All three sampling techniques were essentially equivalent for detection of C. jejuni on fresh carcasses. However, when samples were stored frozen for 7 to 10 d to simulate transport conditions from sampling locations to the laboratory, the incidence of detection was significantly reduced. Use of cryoprotective agents was an effective method to preserve swab samples during frozen storage.

scholarly journals Evaluation of Reliable Digital Elevation Model Resolution for TOPMODEL in Two Mountainous Watersheds, South Korea

2019 ◽  
Vol 9 (18) ◽  
pp. 3690 ◽  
Author(s):  
Daeryong Park ◽  
Huan-Jung Fan ◽  
Jun-Jie Zhu ◽  
Sang-Eun Oh ◽  
Myoung-Jin Um ◽  
...  
Keyword(s):  
South Korea ◽  
Cell Size ◽  
Digital Elevation Model ◽  
River Basin ◽  
Grid Cell ◽  
Dem Resolution ◽  
Digital Elevation ◽  
Mountainous Watersheds ◽  
Elevation Model ◽  
Digital Elevation Model Resolution

This study analyzed the result of parameter optimization using the digital elevation model (DEM) resolution in the TOPography-based hydrological MODEL (TOPMODEL). Also, this study investigated the sensitivity of the TOPMODEL efficiency by applying the varying resolution of the DEM grid cell size. This work applied TOPMODEL to two mountainous watersheds in South Korea: the Dongkok watershed in the Wicheon river basin and the Ieemokjung watershed in the Pyeongchang river basin. The DEM grid cell sizes were 5, 10, 20, 40, 80, 160, and 300 m. The effect of DEM grid cell size on the runoff was investigated by using the DEM grid cell size resolution to optimize the parameter sets. As the DEM grid cell size increased, the estimated peak discharge was found to increase based on different parameter sets. In addition, this study investigated the DEM grid cell size that was most reliable for use in runoff simulations with various parameter sets in the experimental watersheds. The results demonstrated that the TOPMODEL efficiencies in both the Dongkok and Ieemokjung watersheds rarely changed up to a DEM grid-size resolution of about 40 m, but the TOPMODEL efficiencies changed with the coarse resolution as the parameter sets were changed. This study is important for understanding and quantifying the modeling behaviors of TOPMODEL under the influence of DEM resolution based on different parameter sets.

Participative Management of Employees in Decision-Making: An Empirical Study

2018 ◽  
Vol 2 (2) ◽  
pp. 1-5
Author(s):  
B. Ravi Kumar
Keyword(s):  
Decision Making ◽  
Empirical Study ◽  
Sampling Method ◽  
Sampling Methods ◽  
Steel Plant ◽  
Participative Management ◽  
Decision Making Process ◽  
Labour Policy

Participative management of employees in decision-making is considered as a mechanism where workers have a say in the decision making process of an organization. In India WPM is an element of government labour policy. The concept behind this is to improve better relations among employees and workers. The present paper tries to explore about the workers participation in management in Visakhapatnam Steel Plant (VSP) by considering 604 respondent employees of steel plant in order to know their opinions regarding the above mentioned topics by using convenient sampling method, because VSP is big organization consisting of more than 20,000 employees (Both Permanent and Contract). All the employees are busy at their work and it will be difficult to collect the first hand information from the employees by using any other sampling methods except convenient sampling method.

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