Accurate estimation of infiltration rates is crucial for hydrological modeling, impacting predictions of runoff, sediment transport, and related phenomena. Various infiltration models, categorized as empirical, semi-empirical, and physically based, have been developed to compute cumulative infiltration and infiltration rates for these purposes. Because of its simplicity and accuracy, the Green–Ampt (GA) infiltration equation has been widely used for simulating 1-D (vertical) infiltration into the soil. The modification of GA equation by Mein and Larson for steady rainfall conditions (GAML,1973., etc.,) is widely employed in different hydrological modeling software such as ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation), CREAMS (Chemicals, Runoff, and Erosion from Agricultural Management Systems), and WEPP (Water Erosion Prediction Project), suggests the versatility of the model approach. However, its assumption of a sharp wetting front and uniform soil moisture content tends to overestimate low-flow runoff events. The present study proposes a simple, standalone methodology to refine the GAML equation employed for infiltration calculations in the WEPP model. The advantage of the WEPP model is that it can simulate runoff and soil loss events on an hourly, daily, monthly, annual, and event scale; Spatial and temporal distribution of soil loss and deposition can be estimated, and hillslope to watershed scale studies can be performed. Refinement entails estimating hydraulic conductivity (K) and soil moisture (ϴ) distribution in vertical and horizontal (2D) soil matrices before and after ponding scenarios as a linear equation of infiltration. A new algorithm was developed based on the refined GAML (R-GAML) parameters to estimate revised ponding time and infiltration rates based on experimental results, enhancing the accuracy of runoff predictions. Laboratory experiments on sand, clay, and sandy clay soils are utilized to estimate the soil infiltration parameters. The WEPP model was then employed to simulate runoff for a small agricultural watershed with the outlet at T. Narasipura station (of Cauvery River, India). The R-GAML and conventional GAML equations were used for runoff simulation and validated with the observed runoff data. The overestimation of low-flow runoff events using the conventional GAML was substantially reduced by the newly developed method, and the performance of R-GAML versus GAML was evaluated using correlation coefficient (0.937, 0.905), RMSE (16.471, 35.905), and NSE (0.968, 0.915) performance matrices for the Indian context.  Furthermore, this research aims to extend i) runoff and sediment yield (SY) simulation using the R-GAML equation from the field scale to the river basin scale (upscaling), ii) study the impact of Land Use and Land Cover (LULC) change on runoff and SY production by multi-site and multi-temporal calibration approach using the WEPP model. The findings offer valuable insights for urban planners in designing drainage networks, for agricultural water management in scheduling reservoir water release, and for deriving Best Management Practices (BMPs) in the Cauvery basin, which faces transboundary challenges due to rising water demand.

How to cite: Suliammal Ponnambalam, V. and Dasika, N. K.: Innovations in Hydrological Modeling: A Standalone Approach to GAML Equation Enhancement for Runoff and Sediment Yield Estimation Using WEPP model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3323, https://doi.org/10.5194/egusphere-egu24-3323, 2024.

Concentrated runoff increases erosion and moves fine sediment and associated agrichemicals from upland areas to stream channels. Ephemeral gully erosion on croplands in the U.S. may contribute more of the sediment delivered to the edge of the field then from sheet and rill erosion. Typically, conservation practices developed for sheet and rill erosion are also expected to treat ephemeral gully erosion, but science and technology are needed to account for the separate benefits and effects of practices on each of the various sediment sources.

Watershed modeling technology has been widely developed to aid in evaluating conservation practices implemented as part of a management plan, but typically lacks the capability to identify how a source, such as sheet and rill erosion, ephemeral gully erosion, or channel erosion, is specifically controlled by a practice or integrated practices. The U.S. Department of Agriculture’s Annualized Agricultural Non-Point Source pollutant loading model, AnnAGNPS, has been developed to determine the effects of conservation management plans on erosion and provide sediment tracking from all sources within the watershed, including sheet and rill, ephemeral gully, and channel erosion. 

This study describes the ephemeral gully erosion capabilities within the AnnAGNPS model and discusses research needs to further improve these components for integrated conservation management planning.  Conservation management planning by agencies within the U.S. and by international organizations requires a systematic approach when determining the extent of ephemeral gully erosion impacts on a field, watershed, or national basis, and/or to predict recurring or new locations of ephemeral gullies prior to their development.  This technology provides the capability to separate the impact of ephemeral gullies on erosion from other sources and then evaluate the impact of targeted practices to control erosion at the source and subsequent downstream resources.

How to cite: Bingner, R., Wells, R., Momm, H., and Locke, M.: Enhanced Ephemeral Gully Erosion Science within AnnAGNPS , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6677, https://doi.org/10.5194/egusphere-egu24-6677, 2024.

The current evolution of climate in Southern Europe, apparently enhances the frequency and persistence of rainless spells, with interspersed short and intense rainfall events. Both circumstances exacerbate the soil erosion episodes, particularly in the olive cropped landscapes, with the consequent risk of soil productivity loss and the dispersion of pollutants. The most common erosion form, gully erosion, act as preferential ways for the removal and dispersal of runoff and sediments.

Although the near-future climate scenarios are uncertain, new and more effective integrated management systems need to adopted to preserve both the food generation potential, and the environment.

The purpose of this work is to analyze some techniques for the assessment of the gully erosion, from the photo-interpretation of the sequence of historical photograms, including Machine Learning methods to avoid the subjectivity of the observer, to the acquisition of new multi-spectral images with UAV. The nest step is the selection of the optimal location of the prevention, such as cover crops and vegetative barriers, and control, like check-dams for the interception of runoff and sediments.

The final outcome of the proposed techniques is the use of the fill-and spill concept to enhance an intermittent connectivity in the gully networks with the additional advantage of the increased biodiversity in the landscapes.

How to cite: González Garrido, P., Peña, A., Vanwalleghem, T., and Giráldez, J. V.: Analysis of some gully control techniques for the conservation of olive cropped landscapes in Southern Spain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7648, https://doi.org/10.5194/egusphere-egu24-7648, 2024.

Ephemeral gullies (EGs) are channels that form in low parts of the field where runoff concentrates, and are often responsible for considerable soil loss from agriculture fields. Unfortunately, predicting the gradual development of gullies in response to storm events remains challenging. The United States Department of Agriculture has developed several modeling tools to predict the location and dimensions of ephemeral gullies and the resulting soil loss. The tool described herein combines precise geospatial determination of EG pathways with soil erosion and delivery calculations for both those pathways and the contributing hillslopes.

Considering the vital importance of determining runoff concentration for EG development, high-resolution (0.5 ~ 3 m) terrain elevation data are processed with specialized geospatial tools to determine topography-driven surface runoff patterns and define swales where concentrated flows occur.  This creates integrated surface drainage descriptions defining hillslope areas where sheet-and-rill erosion predominates, and swales where EG gullies may develop. This results in detailed flow maps covering entire fields, optionally considering oriented roughness created by crop rows on flow distribution.  These data, along with topography-derived parameters and spatial distributions of soil types and vegetation cover, form the digital landscape description for erosion modeling.

The magnitude, frequency, and seasonal distribution of storms are represented by a synthetic series of events derived from long-term climate databases created for the RUSLE2 (Revised Universal Soil Loss Equation, version 2) model.  Runoff for each storm event is estimated with RUSLER (RUSLE2-Raster), a two-dimensional (2D) raster implementation of RUSLE2 technology that calculates runoff and sheet-and-rill soil loss for all flow paths covering a field.  The RUSLER calculation provides the spatial and temporal distribution of incoming runoff and sediment loads necessary for the calculation of erosion and deposition in the EG channels.

The channel flow and sediment transport model EphGEE (Ephemeral Gully Erosion Estimator) employs an excess shear stress approach to determine where flow erosive forces cause soil detachment and transport, and where deposition occurs.  EphGEE also calculates the rates at which channels locally deepen and widen, thus predicting how channel geometry evolves during each storm, which depends strongly on knowledge of soil erodibility parameters. EphGEE attempts to estimate how erodibility parameters vary in time and with depth using management operations data available from RUSLE2 databases. In most cases, however, field data and parameter calibration are still necessary.

This modeling approach has been applied to monitored fields in the United States.  It was successful in determining runoff and concentrated flow paths, resulting in good predictions of locations where gullies form and how they connect to runoff-generating areas.  For tilled fields where a less erodible soil layer exists, the model provides good approximations of gully depths and widths. For no-till and pasture-to-crop transitions, where EG cross-sectional shapes may be dependent on how erodibility varies with soil depth, better data or prediction methods are needed to improve model performance.

How to cite: Vieira, D., Wells, R., Yoder, D., and Bingner, R.: Event Based Modeling of Ephemeral Gully Development in Agricultural Fields, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12354, https://doi.org/10.5194/egusphere-egu24-12354, 2024.

The severe erosion problems affecting large areas of olive groves on slopes in Andalusia (Spain), whose soil losses exceed 40 kg m-2an  in extreme rainfall events, require an integrated watershed management run by landowners and state or regional agencies.

The most common, and most severe erosion form is gully erosion. Gullies act as preferential ways through which soli particles with adsorbed nutrients and agrochemical substances spread downslope moved by surface runoff, what implies a great water loss.

During the last four years a cooperative innovation project between the University of Cordoba and two joint venture groups to (i) evaluate the extent of the soil loss in selected slopes, (ii) estimate the density and location of check-dams to intercept the water and sediment flows; (iii) design a novel type of modular dams; and (iv) complement th conservation works with new cover crops mixtures.

A by-product of this project is the development of an automatic model for the spatiotemporal evolution of gully networks based on the D8 flow direction algorithm, and a network branches detection scheme to accumulate flow identifying the final outlet.

This model has been successfully applied to two olive cropped slopes of Southern Spain.

The innovative proposal has allowed for: (a) Generation of the DEM (Digital Elevation Model) for hydrological modeling of watersheds and determination of gullies and areas vulnerable to erosion; (b) Development of algorithms for a topologically connected network of gullies to establish the areas of origin of soil loss and sediment deposition (c) Protection and correction of ephemeral and deep gullies in pilot plots by means of dikes of modular pieces, vegetation covers in crop roads, protection of roads and vulnerable areas through native plantations, and burying of pruning remains; (d) Monitoring and follow-up of measures from LiDAR sensors on board UAVs and soil analysis before and after extreme events.

These initiatives have already been successfully tested in several projects in which the University of Cordoba participates, such as the CPI INNOLIVAR project and the HIDROLIVAR Operational Group and will be implemented in new study basins where excellent results are expected due to the fragility of steep slope olive groves in very degraded soils.

How to cite: Peña, A., González-Garrido, P., Laguna, A. M., and Gámiz, A. M.: Automatic generation of topologically connected gully networks for integrated erosion control in sloping olive orchards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12394, https://doi.org/10.5194/egusphere-egu24-12394, 2024.

Ephemeral gullies (EGs) are major contributors to sediment loss and land degradation on cultivated lands. EG is an important linear erosion feature, often occurring at mid-slope position, that can be greatly influenced by upslope and lateral inflow. This study quantified the ephemeral gully erosion influenced by the upslope and lateral inflow, and the results showed that upslope and lateral inflow both contributed to the runoff connectivity of the EG channel and lateral rills in the EG system. For these simulated conditions, upslope inflow contributions to total runoff and soil loss were 62–78% and 65–81%, respectively, while lateral inflow only contributed around 10%. The contribution differences could be attributed to flow hydrodynamic characteristics in that shear stress and stream power in the EG channel were 4.9–8.6 times greater than those on the lateral slopes. From sheet flow to rill flow and EG channel flow, the flow regime gradually shifted from laminar and subcritical flow to turbulent and supercritical flow. The flow force, power, and energy correspondingly increased as the flow regime changed toward turbulent and supercritical. Both field monitoring and indoor simulation displayed the additional sediment delivery caused by upslope sediment-laden flow, verifying the transport-dominated sediment regime in EG systems. In field observations, the sediment increment coefficient (SIC, ratio of net sediment delivery caused by upslope sediment-laden flow to the total sediment delivery) on an event scale varied from 4.6% to 88.6%. In indoor simulations, the SIC changed from 24.9% to 87.5%. The SIC linearly decreased as the sediment concentration of upslope inflow increased. Field monitoring showed complicated phenomena because of natural random variations. SIC also generally decreased as the sediment concentration of upslope inflow increased. Laboratory simulations verified the field monitoring results of extreme rainfall events with large rainfall amounts and intensities. In future studies, multiple morphological criteria defining EG under various environments are urgently needed. Similar to the continuous sediment transport equations for rill erosion, continuous sediment transport equations for EG erosion need to be developed.

How to cite: Xu, X.: Quantification Studies on Ephemeral Gully Erosion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14301, https://doi.org/10.5194/egusphere-egu24-14301, 2024.

I am a doctoral candidate in University of Trento (first year) in Earth Observation at the Department of Civil, Environmental and Mechanical Engineering. My administrative University is Sapienza University of Rome and I am writing to express my interest in presenting my research in developing the strategies to predict Rill and Gully erosion in EGU general assembly 2024.

Soil moisture plays a major role in assisting crop productivity and weather forecasting to satisfy the ever-growing demands for land resources.

Soil erosion mechanics involve fluid (water/wind) detachment or entrainment followed by transport of soil particles and subsequent deposition as soil sediment. Soil movement by water often starts when a raindrop impacts the soil surface and initiates splash erosion, i.e., raindrops break aggregates into finer soil particles, displacing those particles and aggregates to create depressions in the soil surface. It depends on rainfall intensity, soil erodibility, and field slope among other factors. 

Various factors affecting soil erosion, including soil slope and length or supporting control practices like contour rows, strip cropping, and terrace systems, were recognized as independent factors influencing soil erosion by their inclusion in regional soil-loss equations. Water Erosion Prediction Project has been used to predict soil loss in a range of environments such as rangeland and forest for simulating runoff and sediment yield from the untreated watershed with good accuracy using continuity equation :

(dG/dx)  =  D_r + D_i 

G = sediment load (kg·s^-1· m^-1)

x = distance down slope (m)

D_r = rill erosion rate (+for detachment, - for deposition)

D_i = interrill sediment delivery (kg·s⁻¹·m⁻²).

Water Erosion Prediction Project relates sediment load in the runoff to the distance downslope as a function of the interrill and rill erosion rates calculated on a daily time step. Interrill erosion is the process of sediment delivery to more concentrated flow in rills, but rill erosion depends on the potential detachment capacity as limited by the sediment transport capacity of runoff in the rill. Soil loss through interrill and rill erosion is associated with the factor known as Revised Universal Soil Loss Equation (RUSLE), formulated as :

A  = R∗K∗L_s∗C∗P

A is the annual soil loss due to erosion [t/ha year];

R the rainfall erosivity factor;

K the soil erodibility factor;

L_S the topographic factor derived from slope length and slope gradient;

C the cover and management factor; and

P the erosion control practice factor.

The limitations of RUSLE are that it only accounts for soil loss through sheet and rill erosion and ignores the effects of gully erosion. 

The objective is to generate gully erosion susceptibility maps (GESMs) by applying three machine learning algorithms to identify the area of the basin with respect to total area, which prones to have higher or lower susceptiblity to gully erosion.

These erosions require Persistent Monitoring with the combination of three main elements. High resolution, Revisit rate and global coverage. The models can be developed using GIS or R software and from SAR technologies.

Considering my academic performance so far, I hope to have this opportunity to present in EGU assembly, as I am confident that I will be able to meet your expectations.

Thanking you.

How to cite: Kaparthi, H. V. and Vitti, A.: Development of observation model for predicting the phenomena of Rill and Gully erosion using Machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6562, https://doi.org/10.5194/egusphere-egu24-6562, 2024.