An approach to identifying and evaluating the potential formation of ephemeral gullies in the conditions of the Czech Republic

Abstract

Soil erosion, including ephemeral gully erosion, is a serious degradation process in the Czech Republic. It currently threatens more than half of the agricultural acreage through negative changes in the whole complex of soil properties. The unfavourable consequences of surface runoff are seen in the erosion processes degrading agricultural soils. The South Moravia Region was selected as the case study area – mainly for its natural conditions and high soil degradation risk . A set of data, collected from 2012 to 2017 in a maize-growing area, especially on deep loess soils in the South Moravia Region, was used to analyse the morphological characteristics of the ephemeral gullies (EGs). The relationship was confirmed between the ephemeral gully (EG) length and the size of its contributing drainage area in accordance with studies conducted in other countries. It is also important that the closest relationship was confirmed between the length of the gully and its calculated volume. Dependence was sought on the data of 51 cases of the detailed, measured and evaluated EGs. These results will become the basis for finding a predictive relationship and the quantification of EG erosion. Locating EGs and predicting their length is crucial for estimating the sediment load and planning conservation strategies. The aim of this paper is to contribute to the understanding of this issue, i.e., define and verify the basic crucial causal factors and propose guidelines for locating the potential EG occurrence and predicting the sediment load. A research effort to better understand the EG mechanism and causal factors over a wide range of watershed conditions is fundamental to the establishment of basic rules for the adoption of optimal conservation strategies.

Sediment Delivery Ratio from a small Semiarid Watershed of Brazil

“…Similar results were obtained by Silva et al (2020) evaluating the effect of different levels of coverage soybean straw on interrill erosion and runoff. The infiltration rates higher showed for soil with semi-shrubby Caatinga vegetation and soil with herbaceous residue in decomposition due roughness height decrease runoff volume favoring to water infiltration capacity, soil roughness potentially affects surface processes such as infiltration (Piscoya et al, 2018b;Dumbrovsky et al, 2019).…”

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

“…Defining the threshold values for the EG identification can differ according to the morphology conditions. We used the upslope contributing area of 500 and 300 grid cells according to the research by Dumbrovský et al (2020). A similar approach was used by Zhang et al Process A: based on the HCU algorithm, the pixels intersected with the surface runoff barriers are extracted as NoData from the DTM  CSA (inputs: result from procedure C)  flow direction algorithm D∞ (from corrected DTM)  flow accumulation algorithm  identification and extraction of the ephemeral gullies and valleys as NoData from the flow accumulation raster based on the EG3 algorithm  UCA raster = the input for the L calculation according to Equation (6) Process B: slope algorithm (from input DTM)  the exponent "m" calculation according to Equation (4) = input for the L calculation according to Equation (6) Process C: slope algorithm (from input DTM)  slope extraction algorithm for the extraction given the slope categories according to Figure 3 (the result is the input for the CSA algorithm in process A and Equations ( 2)-(3)  the inputs for the S calculation according to Equations (2) and (3) Process D: calculation according to Equations (2), ( 3), (6)  the raster values with L, S and LS values (2017) for excluding large valleys.…”

“…According to the abovementioned definition by Wischmeier and Smith (1978), we extended the UCA method by another assumption of the exclusion of larger ephemeral gullies (EGs) defined by Dumbrovský et al (2020). This assumption is based on the original principles of USLE/RUSLE which only enable the calculation of sheet and rill erosion.…”

“…The EGs represent a border when the rills transform into gullies and, at least, the larger gullies, the valleys and the channels should be excluded. According to Dumbrovský et al (2020), the contribution area of the EG is 3-5 ha, therefore, when the resolution is 10 m, then the contributing area represents 300-500 grid cells. Similar to Tarboton,s et al (1991) methodology for the channels are identified the gullies as the grid cells exceeding the threshold values of the accumulated area array matrix.…”

Clay mineralogical composition and chemical properties of Haplic Luvisol developed on loess in the protected landscape area Litovelské Pomoraví

“…Pecsi, 1990;Smalley, Markovič, & Svirčev, 2001;Sprafke & Obreht, 2016;Wright, 2001), stratigraphy (e.g. Antoine et al, 2013;Markovič et al, 2008;Thiel, Horváth, & Frechen, 2014), geotechnical stability (Dumbrovský, Drbal, Sobotková, & Uhrová, 2020;Tu, Kwong, Dai, Tham, & Min, 2009) and the industrial application of loess (Arsenovi c, Pezo, Manči c, & Radojevi c, 2014). Smalley et al (2001) highlighted two major approaches to loess: "soil science" and "sedimentology".…”