Interrill Erosion Rates Research Articles

Rainfall Simulation as a Tool for Teaching Process Dynamics

Greater understanding of the basic processes of hillslope erosion, infiltration, runoff and nutrient removal can be achieved by using rainfall simulators. The modified Kamphorst simulator provides a simple, cost-effective way to teach students the dynamics of earth surface processes that shape our landscapes. The exercise described here can be adapted for use in introductory or advanced earth science courses, or it can be expanded to form the basis of a bachelor's dissertation. The simulator allows the student to examine the controls on interrill erosion rates such as slope angle and rainfall intensity. Continuous measurement of runoff at a known rainfall intensity can be used to estimate infiltration rate, a concept that is exceedingly difficult to teach. The measurement of transported aggregates and associated organic matter provides students with an appreciation for preferential transport and illustrates the concept of enrichment ratios.

Tracked Vehicle Traffic Effects on the Hydrologic Characteristics of Central Texas Rangeland

The initial change and the temporal recovery pattern of hydrologic, soil, and vegetation characteristics following tracked vehicle passage (tracking) were documented in a split-plot experiment. Treatments were characterized by different soil moisture conditions at the time of vehicle passage (wet or dry) and different tracking intensities (0, 1, 4, and 10 passes by a M2 Bradley Infantry Fighting Vehicle). The study was conducted at Fort Hood, located in the Cross-Timber Prairie ecological resource zone of Texas. Dry-tracked (tracking disturbance imposed on dry soil) plots did not have significantly different infiltration rates or interrill erosion than control plots at any time during the study. In contrast, wet-tracked (tracking disturbance imposed on wet soil) plots had significantly lower infiltration and significantly greater interrill erosion rates, with the initial response and the period of recovery being greater as the number of vehicle passes increased. Bulk density in the top 50 mm was the variable most strongly correlated with infiltration rate immediately following the vehicle traffic. This correlation decreased with passage of recovery time and the strongest predictive factor became the percent exposed soil. This change can be attributed to the natural amelioration (e.g., clay expansion and contraction associated with wetting and drying, activity of soil biota) of soil structure and the death and decomposition of bunchgrasses in the tracks which were replaced by annual grasses and forbs that provided less cover. After two years the soil structure, vegetation cover and standing crop had recovered to the point that there was no longer any significant difference between treatments in their collective influence on infiltration rate or interrill erosion.

Interrill erodibilities based on the rainfall intensity flow discharge erosivity factor

Interrill erodibilities are often determined using a model which considers the interrill erosion rate to vary directly with rainfall intensity (I) squared. However, it has been shown that the sediment discharge from an interrill area varies directly with I rather than I2 when factors such as flow discharge are also considered. Analysis of data from the experiments used to determine interrill erodibilities in the Water Erosion Prediction Project (WEPP) in terms of a model that uses both rainfall rate and flow discharge indicates that the susceptibilities of some soils to interrill erosion may differ considerably from the erodibilities determined from the WEPP model. Apart from the need to use models which better account for the variations in erosive stress, consideration has to be given to the fact that erodibility is a dynamic factor that can vary rapidly between two extremes. One of these extremes is associated with detachment-limiting conditions that may often be controlled by cohesion. The other extreme is associated with the complete protection of the soil matrix by a layer of pre-detached particles. When this extreme results, interrill erodibilities are controlled by the particle size and density characteristics of the pre-detached particles. Difficulties arise in extrapolating information from one scale to another, and from one soil where erodibility experiments have been performed to others where they have not because of the dynamic nature of the rain-flow-soil surface interaction. Also, the effect of slope gradient in the interrill erosion environment varies between soils and experimental conditions because of this interaction and the differing susceptibility of soils to rilling.

The Spatial and Temporal Influence of Vegetation on Surface Soil Factors in Semiarid Rangelands

Technology for modeling runoff and erosion on rangelands has improved, but improvements in simulation accuracy are often lost in techniques used to estimate model parameters. This is particularly true on semiarid rangelands which have significant spatial and temporal variations in runoff and erosion processes. The spatial distribution of the amount and kind of vegetation is an important factor controlling infiltration and erosion rates on rangelands. Improvements in model parameter estimation techniques and in our understanding of vegetation and soil induced variability are needed to increase our hydrologic and erosion predictive capabilities for rangelands. The role vegetation performs in controlling the spatial and temporal variability of surface soil properties that influence infiltration and erosion on semiarid rangelands was investigated using data representing a northwest sagebrush plant community and a southern great plains bunchgrass/sodgrass plant community. Vegetation was found to be the primary factor influencing the spatial and temporal variability of surface soil processes controlling infiltration and interrill erosion rates on semiarid rangeland. On sagebrush dominated landscapes, vegetation growth form (e.g., bunchgrass, sodgrass, shrub) is the primary factor influencing surface soil factors that control infiltration and erosion rates. On grass dominated landscapes the temporal response of surface soil factors induced by normal variations in climate, plant cover and biomass is greater than the spatial variability induced by grass growth form. To improve the utility of models for use on rangeland we must fully recognize that the rangeland system is spatially and temporally influenced by the amount and growth form of native vegetation.

Time-Effect on Water Erosion for Ridge Tillage

Ridge tillage is a reduced-tillage farming practice where ridges are formed in the growing season during cultivation for weed control. Some disagreement exists in the literature about whether the practice reduces soil erosion by water. To address this question, two soils were studied with ridges of varying age to determine the effect of time on interrill and rill erosion rates. The soils studied included a somewhat poorly drained Rossmoyne silt loam and a poorly drained Hoytville silty clay. Simulated rainfall was applied prior to spring planting to study interrill and rill erosion on freshly formed and consolidated ridges. Surface residue was carefully removed so that age of ridge differences only were studied. For each soil, three ridge ages were studied: freshly formed, two and seven years old; freshly formed, four and eight years old for Hoytville and Rossmoyne, respectively. In both soils, the older consolidated ridges had significantly lower interrill erosion rates and sediment concentrations compared to the freshly formed ridges. The mean interrill erosion rate was 40 and 59% lower than the freshly formed ridges for Hoytville and Rossmoyne, respectively. For both soils, the rill erosion rate for the older ridges was reduced 72% compared to the freshly formed ridges. However, no differences were found between the older ridges in either soil for both interrill and rill erosion. A relationship between rill erosion rate and hydraulic shear was found for the freshly formed ridges in both soils, but not for the older ridges. The older consolidated ridges were found to effectively reduce soil loss as compared to the freshly formed ridges.

INTERRILL ERODIBILITY: COLLECTION AND ANALYSIS OF DATA FROM CROPLAND SOILS

ABSTRACT Interrill erodibility was measured on eighteen cropland soils in the western half of the United States, using a rotating boom rainfall simulator. There were significant differences in infiltration rates, runoff rates, and erosion rates among the soils. A slope factor, based on plot slope, to account for differences observed in interrill erosion rates, is proposed. The data show that this slope factor may also be a function of soil properties. An interrill erodibility coefficient is proposed for each soil.

Evaluating Interrill and Rill Erodibilities for Soils of Different Textures

ABSTRACT Soil loss rates were evaluated on row-sideslope and row-furrow plots for three soils: one relatively high in sand, one in silt, and one in clay. Interrill erosion rates were measured on plots constructed from a 0.91-m section of furrow. Rill erosion rates were determined on separate 9.3-m sections of graded (0.035) row furrows by apportioning the total soil loss with respect to contributing areas. The interrill and rill erodibilities of each soil were then computed from the erosion rate data. Comparison of the erodibilities showed that the relationship among soils' rill erodibilities may vary greatly from both the relationships among their interrill erodibilities and among their site-specific USLE K-factors..

SOME HYDROLOGIC IMPACTS OF PLOWING RANGELAND SOILS1

ABSTRACT: Rainfall simulator studies were conducted during 1982 and 1983 on agricultural and native rangeland soils of the same soil series in northern Utah. Results indicate that the same soil series mapped at different locations on agricultural land will have similar 10, 20, and 30 minute infiltration rates and similar interrill erosion rates. Seasonal differences in infiltration and erosion rates were significant. Comparisons between agricultural and native soils were complicated by three‐way statistical interactions. Seasonal variations in both infiltration rates and erosion rates were greatest on agricultural soils. Of four soil series on native rangeland, only one showed significant seasonal variation in infiltration rates, while erosion rates were similar across all seasons for all soil series. Soil and cover factors important in predicting infiltration and erosion were identified.

Erosion Characteristics of Three Northwestern Soils

ABSTRACT THREE Pacific Northwest soils were collected and tested under typical Midwestern rainfall conditions. The soil was placed in plots where rills were formed on the surface. Runoff and soil loss were collected and measured from the rills and interrill areas. Soil loss splashed off the sides, top and bottom of the plots, was also measured. Rill erosion rates from these soils compared favorably to three Midwestern soils identically treated. Interrill erosion rates were somewhat higher from the Northwest soils. Soil transport mechanisms were similar for the soils. In general, the three Pacific Northwest soils behav-ed similarly to the Midwestern soils indicating that soil differences are probably not major factors contributing toward differing Northwest erosion characteristics.

Effects of Livestock Grazing on Infiltration and Erosion Rates Measured on Chained and Unchained Pinyon-Juniper Sites in Southeastern Utah

Effects of Livestock Grazing on Infiltration and Erosion Rates Measured on Chained and Unchained Pinyon-Juniper Sites in Southeastern Utah

Runoff, Erosion, and Nutrient Movement from Interrill Areas

ABSTRACT THE influence of rainfall and over-land flow on interrill erosion and associated nutrient losses was studied for flatland conditions. Interrill ero-sion rates were substantially large. However, amounts of eroded soil reaching actual stream systems may be greatly reduced, depending on the severity of storms. Interrill erosion rates can be decreased substantially by improved tilth. In soils with excellent tilth, the silt fraction in the eroded soil was higher than in the original soil and the clay and sand fractions were lower. Although N and P concentrAtions in the soils with excellent tilth were quite high, losses of these nutrients in sediment runoff were low because of increased infiltration.