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.

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.

Spatially uniform surface runoff as a result of erosion-induced high hydrolocial conncenctiviey over an extremelydegraded catchment 

2021 ◽  
Author(s):  
Mingguo Zheng
Keyword(s):  
Surface Runoff ◽  
High Flow ◽  
Chinese Loess Plateau ◽  
Slope Length ◽  
Chinese Loess ◽  
Erosion Processes ◽  
Annual Time ◽  
Semi Arid ◽  
Experimental Plots ◽  
The Chinese Loess Plateau

<p>Previous studies have suggested that runoff reduces with slope length, and the scaling trend diminishes with the degree of land degradation. This study further hypothesized that runoff is scale-independent and spatially uniform in extremely degraded landscapes. We tested the hypothesis on the Chinese Loess Plateau. Runoff data were collected from a densely rilled and gullied loess headwater with soil erosion intensity close to 20,000 t km-2 yr-1.  The data included observations from seven arable experimental plots of various lengths (20 to 164 m) and gradients (9 to 32°), as well as the headwater outlet. The results showed that the erosion-induced network of rills and gullies lowered runoff reinfiltration and resulted in exceptional high flow connectivity, thus obscuring the effects of other environmental conditions (mainly topography) and contributing to uniform runoff from the upper hillslope to the headwater outlet. The observations held at the event, annual, and mean annual time scales, implying that the investigated watershed is simply the sum of individual slopes. This study highlights the effect of erosion processes on the ensuing runoff yield. The effect should be fully addressed in studies of runoff yield in semi-arid areas, which are among the most erodible landscapes due to sparse land cover.</p>

An Experimental Study on the Rainfall-Runoff Progress of Wheat under Different Slope Angle

2014 ◽  
Vol 912-914 ◽  
pp. 1986-1994
Author(s):  
Na Na Zhao ◽  
Fu Liang Yu ◽  
Chuan Zhe Li ◽  
Jia Liu ◽  
Hao Wang
Keyword(s):  
Regression Analysis ◽  
Soil Moisture ◽  
Power Function ◽  
Surface Runoff ◽  
Rainfall Intensity ◽  
Slope Angle ◽  
Subsurface Flow ◽  
Rainfall Runoff ◽  
Determination Coefficient ◽  
Initial Soil

Rainfall-runoff process plays an important role in hydrological cycle, and the study on the rainfall-runoff will provide foundation and basis for research on basin hydrology and flood forecasting. In this paper, the surface runoff and subsurface flow of wheat were observed in the laboratory by artificial rainfall, and analyzed the cumulated surface runoff and recession process of subsurface flow by regression analysis. In addition, the factors affected the runoff and response of soil moisture on the runoff coefficients was also discussed. Results showed that the rainfall intensity, soil coverage and slope had important influence on the surface runoff generation, and the surface runoff was observed when the total rainfall amount exceeded 32mm and 13mm for 5°and 15° slope respectively. The cumulative surface runoff could be expressed as a power function, which had higher determination coefficient R2 (0.92~0.999). The subsurface flow was only observed at the ripening period and wheat stubble treatment, and mainly affected by slope angle and initial soil moisture, whereas rainfall intensity showed little impact. The recession curve of subsurface flow can be described as a simple exponential expression or power function, which the determination coefficient was 0.88 and 0.94 by regression analysis, respectively. Moreover, there was an obvious threshold (approximately 30%) between the average initial soil moisture and runoff coefficients, which the runoff increased significantly as above the threshold.

Assessment of surface runoff depth changes in Sǎrǎţel River basin, Romania using GIS techniques

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Costache Romulus ◽  
Fontanine Iulia ◽  
Corodescu Ema
Keyword(s):  
River Basin ◽  
Surface Runoff ◽  
Land Use Changes ◽  
Curve Number ◽  
Annual Rainfall ◽  
Average Annual Rainfall ◽  
Runoff Depth ◽  
Gis Environment ◽  
Quantitative Changes ◽  
Scs Cn

AbstractSǎrǎţel River basin, which is located in Curvature Subcarpahian area, has been facing an obvious increase in frequency of hydrological risk phenomena, associated with torrential events, during the last years. This trend is highly related to the increase in frequency of the extreme climatic phenomena and to the land use changes. The present study is aimed to highlight the spatial and quantitative changes occurred in surface runoff depth in Sǎrǎţel catchment, between 1990–2006. This purpose was reached by estimating the surface runoff depth assignable to the average annual rainfall, by means of SCS-CN method, which was integrated into the GIS environment through the ArcCN-Runoff extension, for ArcGIS 10.1. In order to compute the surface runoff depth, by CN method, the land cover and the hydrological soil classes were introduced as vector (polygon data), while the curve number and the average annual rainfall were introduced as tables. After spatially modeling the surface runoff depth for the two years, the 1990 raster dataset was subtracted from the 2006 raster dataset, in order to highlight the changes in surface runoff depth.

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.

Effects of DEM horizontal resolution and methods on calculating the slope length factor in gently rolling landscapes

CATENA ◽  
2011 ◽  
Vol 87 (3) ◽  
pp. 368-375 ◽  
Author(s):  
Honghu Liu ◽  
Jens Kiesel ◽  
Georg Hörmann ◽  
Nicola Fohrer
Keyword(s):  
Horizontal Resolution ◽  
Slope Length ◽  
Slope Length Factor

scholarly journals Influence of the Lineament Geological Features on the Hydrologic Flow Direction of Wadi Al Kuf Catchment Area, Cyrenaica, Northeastern Libya

2019 ◽  
Vol 34 (3) ◽  
pp. 153-164
Author(s):  
Ammar A Ammar
Keyword(s):  
Catchment Area ◽  
Flow Direction ◽  
Rock Fracture ◽  
Main Trend ◽  
Landsat 8 ◽  
Pixel Resolution ◽  
Radar Images ◽  
Set Systems ◽  
Geological Features ◽  
Al Jabal Al Akhdar

Wadi Al Kuf Catchment Area WKCA is one of the largest watershed basins on Al Jabal al Akhdar Cyrenaica anticlinorium, the area is more than 960Km2, and considers as a semi-wet basin. This basin highly affected with lineaments geological features just like morphometric and tectonics types including fissures, fault systems and joints set systems in the highly karst lime stones of Al Jabal al Akhdar group lithological formations. These lineaments phenomena were measured and extracted from the radar images of digital terrain model of 30 meters space grid, and the hyper spectral Landsat 8 of 15 meters pixel resolution, they were processed and interpreted by several geospatial geomatics and geological software. The direction orientation and the rock density of these fissures, fractures, joints set systems, faults and the morphometric dendritic drainage pattern had been measured and illustrated from the rose diagram analysis and the geological map. The mainstream of this catchment area WKCA is the 6th order and mainly parallel to the main trend direction with the first escarpment circular fault at the major orogeny tectonic fault of Al Jabal al Akhdar uplift, and these lineaments features is averaged 58.3o  with the azimuth degree along the mainstream. The drainage density,  lineaments density analysis and distribution of the WKCA have been classified as low lineaments rock fractures in the eastern boundary of the basin, moderate lineaments rock fissures in the middle of the basin and high density of rock fracture in the western and northern boundary of the basin, these had reflected the deep percolations and infiltrations to the ground water-bearing aquifer in the WKCA through the secondary and the tertiary porosity of the hydrological karst system.

scholarly journals Topography significantly influencing low flows in snow-dominated watersheds

2017 ◽  
Author(s):  
Qiang Li ◽  
Xiaohua Wei ◽  
Xin Yang ◽  
Krysta Giles-Hansen ◽  
Mingfang Zhang ◽  
...  
Keyword(s):  
Regression Models ◽  
Low Flow ◽  
Mean Flow ◽  
Slope Length ◽  
Low Flows ◽  
Slope Length Factor ◽  
High Flows ◽  
Flow Variables ◽  
Characterization Index

Abstract. Watershed topography plays an important role in determining the spatial heterogeneity of ecological, geomorphological, and hydrological processes. Few studies have quantified the role of topography on various flow variables. In this study, 28 watersheds with snow-dominated hydrological regimes were selected with daily flow records from 1989 to 1996. The watersheds are located in the Southern Interior of British Columbia, Canada and range in size from 2.6 to 1,780 km2. For each watershed, 22 topographic indices (TIs) were derived, including those commonly used in hydrology and other environmental fields. Flow variables include annual mean flow (Qmean), Q10%, Q25%, Q50%, Q75%, Q90%, and annual minimum flow (Qmin), where Qx% is defined as flows that at the percentage (x) occurred in any given year. Factor analysis (FA) was first adopted to exclude some redundant or repetitive TIs. Then, stepwise regression models were employed to quantify the relative contributions of TIs to each flow variable in each year. Our results show that topography plays a more important role in low flows than high flows. However, the effects of TIs on flow variables are not consistent. Our analysis also determines five significant TIs including perimeter, surface area, openness, terrain characterization index, and slope length factor, which can be used to compare watersheds when low flow assessments are conducted, especially in snow-dominated regions.

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