AGNPS GIS-Based Tool for Watershed-Scale Identification and Mapping of Cropland Potential Ephemeral Gullies

Abstract

The formation of ephemeral gullies in agricultural fields has been recognized as an important source of sediment contributing to environmental degradation and compromising crop productivity. Methodologies are being developed for assessing gully formation and gully sediment yield. The Annualized Agricultural Non-Point Source (AnnAGNPS) pollution model is an important tool for multi-temporal watershed-scale simulations because it contains the necessary components for ephemeral gully investigation, making AnnAGNPS a commonly used tool for evaluations of agricultural conservation and operation practices. AnnAGNPS requires the user to define the location of ephemeral gullies throughout the watershed, what often constitutes a time consuming task where users may not accurately locate and describe all ephemeral gully locations. Alternatively, herein a GIS-based graphical user interface is described for the automated identification of areas with high probability of forming ephemeral gullies, referred to as potential ephemeral gullies (PEGs), based on the modified Compound Topographic Index (CTI). Through the aid of a study case, PEG mouth locations along with their attributes are generated through an iterative procedure by varying different CTI threshold values (99.9%, 99.5%, 99.0%, 98.5%, and 98%). Three sets of yielded PEG mouth locations and corresponding attributes were then integrated with AnnAGNPS for assessment of the impact of potential ephemeral gullies in the watershed sediment erosion. Analysis of the spatial distribution of estimates of annual average of gully erosion identifies the sub-watersheds prone to ephemeral gully erosion, thus enhancing the applicability of AnnAGNPS to evaluate conservation practices and/or targeted interventions designed to address ephemeral gully erosion at the watershed-scale.

Integrated Technology for Evaluation and Assessment of Multi-Scale Hydrological Systems in Managing Nonpoint Source Pollution

“…Capabilities of the AnnAGNPS model for agricultural studies include tools to estimate the effect of crop growth, canopy cover, root mass, fall height, and soil disturbance by farming equipment based on detailed input parameters characterizing farming management schedule and operations in time and space. The AnnAGNPS model contains tools to estimate loads from ephemeral gully sources [33,34] and potential loads reduction due to conservation practices, such as riparian vegetation strips [35] and sedimentation ponds [9,14].…”

“…One important source of sediment erosion and transport is ephemeral gully. The AnnAGNPS watershed pollution model already contains modules to estimate the contribution of ephemeral gullies [33] and this source is considered an important, but yet not addressed, source of nonpoint source pollution in the U.S. Midwest region. Similarly, the impact of existing conservation structures, such as riparian vegetation strips and sediment retention ponds, will be implemented.…”

The effects of topography and soil properties on radiocesium concentrations in forest soils in Fukushima, Japan

“…Thus, where water pools, at the flat or concave surface, Cs-137 levels are higher and have migrated to a further depth (Schimmack et al, 1994;Schimmack et al, 1989;Teramage et al, 2014). In general, slope degrees and curvatures -particularly profile and plan curvatures -are considered some of the most influential factors in hydrology and soil transport on a sloped surface; hence, they also influence Cs-137 movement (Gessler et al, 1995;Heimsath et al, 1997;Momm et al, 2012;Moore et al, 1993;Tesfa et al, 2009). Topographic wetness is one of the two most powerful and most frequently used surface hydrology indices, along with the stream power index (Hengl and Reuter, 2008).…”

Spatial Characterization of Riparian Buffer Effects on Sediment Loads from Watershed Systems

“…If the drainage area of a flow profile is greater than the threshold value provided, the LTE is set to 0, and the calculations proceed as described in the previous section. The AGBUF technology has been integrated with the AGNPS Potential Ephemeral Gully technology (Momm et al, 2012), providing an integrated approach to assessing conservation practices affecting tillage and ephemeral gully erosion with the capability of buffers to remove sediment as simulated with AnnAGNPS.…”

“…8). Two potential ephemeral gully initiation points (most downstream point for gully channel initiation) were identified based on evaluation of aerial photographs and the compound topographic index analysis using the AnnAGNPS potential ephemeral gully component (Momm et al, 2012). These ephemeral gully initiation points are marked as red squares in Fig.…”