Modelling artificial channel and land‐use changes and their impact on floods and sediment yield to the Ishikari basin

The potential for flooding and sediment transport is greatly affected by river channel form and changes in land use. Therefore the modelling of channel morphology prior to canalization and of land‐use change is important with respect to the prediction of floods and sediment yield and their consequences. A combination of land‐use transformation maps and soil properties shows certain decision rules for the conversion of forest into arable or vice versa. The model proposed, from this study, was used to simulate possible past and/or future channel and land‐use patterns. Subsequently, the outcome of this simulation was used to assess the risk of flooding, sediment transport and soil‐erosion under different conditions. In this study, channel morphology prior to canalization and land‐use change in the Ishikari basin, Hokkaido, Japan, were analysed by comparing three scenarios using a physical based channel and slope model. The results indicate that pre‐canalization channel morphology has a significant impact on flood peak, but no significant effect on sediment yield. In contrast, land‐use change has a significant effect on soil eroded from hillslopes, but no significant effect on flooding for Ishikari basin. This study also illustrates the challenges that a simple model, such as a physical based channel and slope model, can simulate large‐scale river basin processes using fewer hydrological data resources. Copyright © 2004 John Wiley & Sons, Ltd.     

Modelling the hydrologic effects of dynamic land‐use change using a distributed hydrologic model and a spatial land‐use allocation model

This study develops a novel approach for modelling and examining the impacts of time–space land‐use changes on hydrological components. The approach uses an empirical land‐use change allocation model (CLUE‐s) and a distributed hydrological model (DHSVM) to examine various land‐use change scenarios in the Wu‐Tu watershed in northern Taiwan. The study also uses a generalized likelihood uncertainty estimation approach to quantify the parameter uncertainty of the distributed hydrological model. The results indicate that various land‐use policies—such as no change, dynamic change and simultaneous change—have different levels of impact on simulating the spatial distributions of hydrological components in the watershed study. Peak flow rates under simultaneous and dynamic land‐use changes are 5·71% and 2·77%, respectively, greater than the rate under the no land‐use change scenario. Using dynamic land‐use changes to assess the effect of land‐use changes on hydrological components is more practical and feasible than using simultaneous land‐use change and no land‐use change scenarios. Furthermore, land‐use change is a spatial dynamic process that can lead to significant changes in the distributions of ground water and soil moisture. The spatial distributions of land‐use changes influence hydrological processes, such as the ground water level of whole areas, particularly in the downstream watershed. Copyright © 2010 John Wiley & Sons, Ltd.     

The impact of land use change and check‐dams on catchment sediment yield

Extensive land use changes have occurred in many areas of SE Spain as a result of reforestation and the abandonment of agricultural activities. Parallel to this the Spanish Administration spends large funds on hydrological control works to reduce erosion and sediment transport. However, it remains untested how these large land use changes affect the erosion processes at the catchment scale and if the hydrological control works efficiently reduce sediment export. A combination of field work, mapping and modelling was used to test the influence of land use scenarios with and without sediment control structures (check‐dams) on sediment yield at the catchment scale. The study catchment is located in SE Spain and suffered important land use changes, increasing the forest cover 3‐fold and decreasing the agricultural land 2·5‐fold from 1956 to 1997. In addition 58 check‐dams were constructed in the catchment in the 1970s accompanying reforestation works. The erosion model WATEM‐SEDEM was applied using six land use scenarios: land use in 1956, 1981 and 1997, each with and without check‐dams. Calibration of the model provided a model efficiency of 0·84 for absolute sediment yield. Model application showed that in a scenario without check dams, the land use changes between 1956 and 1997 caused a progressive decrease in sediment yield of 54%. In a scenario without land use changes but with check‐dams, about 77% of the sediment yield was retained behind the dams. Check‐dams can be efficient sediment control measures, but with a short‐lived effect. They have important side‐effects, such as inducing channel erosion downstream. While also having side‐effects, land use changes can have important long‐term effects on sediment yield. The application of either land use changes (i.e. reforestation) or check‐dams to control sediment yield depends on the objective of the management and the specific environmental conditions of each area. Copyright © 2008 John Wiley & Sons, Ltd.     

Long‐term sediment yield from a small catchment in southern Brazil affected by land use and soil management changes

Sediments produced from eroding cultivated land can cause on‐site and off‐site effects that cause considerable economic and social impacts. Despite the importance of soil conservation practices (SCP) for the control of soil erosion and improvements in soil hydrological functions, limited information is available regarding the effects of SCP on sediment yield (SY) at the catchment scale. This study aimed to investigate the long‐term relationships between SY and land use, soil management, and rainfall in a small catchment. To determine the effects of anthropogenic and climatic factors on SY, rainfall, streamflow, and suspended sediment concentration were monitored at 10‐min intervals for 14 years (2002–2016), and the land use and soil management changes were surveyed annually. Using a statistical procedure to separate the SY effects of climate, land use, and soil management, we observed pronounced temporal effects of land use and soil management changes on SY. During the first 2 years (2002–2004), the land was predominantly cultivated with tobacco under a traditional tillage system (no cover crops and ploughed soil) using animal traction. In that period, the SY reached approximately 400 t·km^?2·year^?1. From 2005 to 2009, a soil conservation programme introduced conservation tillage and winter cover crops in the catchment area, which lowered the SY to 50 t·km^?2·year^?1. In the final period (2010–2016), the SCP were partially abandoned by farmers, and reforested areas increased, resulting in an SY of 150 t·km^?2·year^?1. This study also discusses the factors associated with the failure to continue using SCP, including structural support and farmer attitudes.     

Spatial and temporal variations in soil erosion and deposition due to land‐levelling in a semi‐arid area of Basilicata (Southern Italy)

This paper examines the changes from 1955 to 2002 in soil erosion and deposition due to changes in land‐use patterns in the semi‐arid territory of Craco, which is characterized by landsliding and badland erosion. The area underwent continuous degradation during the last century due not only to its lithological vulnerability but also to the anthropic pressure favoured by the introduction of Common Agricultural Policy (CAP) measures, which has led to the reclamation of scrub lands and badlands for durum wheat cultivation. Our analysis integrates the Unit Stream Power Erosion Deposition (USPED) model with a geographic information system (GIS) to quantify erosion risk and predict deposition patterns. Soil data, land use inventory, digital elevation data and climatic atlases were used as resource data sets to generate USPED factor values. The obtained results correlate well with field measured erosion data by other researchers. In the investigated 47 years, stable areas decreased by about 280 ha (3·8% of the total surface area), largely attributable to the increase of the low and moderate erosion intensity without significant change in sedimentation. Results from this study have implications related to understanding the geomorphic response of sites that were abandoned following remodelling due to the application of the F measure of Regulation CEE 2078/92. The average annual erosion rates estimated for abandoned and remodelled sites are respectively 15·99 and 10·64 t ha^?1, meaning that the total amount of erosion in 20 years could be estimated at around 100 t ha^?1. Copyright © 2007 John Wiley & Sons, Ltd.     

Potential wind erosion rate response to climate and land‐use changes in the watershed of the Ningxia–Inner Mongolia reach of the Yellow River,China, 1986–2013

Climate and land‐use changes could strongly affect wind erosion and in turn cause a series of environmental problems. Thus, the objective of this study was to assess potential wind erosion rate (PWER) response to climate and land‐use changes in the watershed of the Ningxia–Inner Mongolia Reach of the Yellow River (NIMRYR), China. The watershed of NIMRYR suffers from serious wind erosion hazards, and over recent decades, wind erosion intensity and distribution has changed, following climate and land‐use changes. To understand these processes in the NIMRYR watershed, the Integrated Wind Erosion Modelling System (IWEMS) and the Revised Wind Erosion Equation (RWEQ) were used to calculate the PWER under different climate conditions and land‐use scenarios, and to assess the influences of climate and land‐use changes on the PWER. The results show the PWER in the whole watershed had a significant declining trend from 1986 to 2013. The results of the relationship among PWER, climate change, and land‐use changes showed that climate change was the dominant control on the PWER change in this watershed. Compared to the period 1986–1995, the average PWER decreased 23.32% and 64.98% as a result of climate change in the periods 1996–2005 and 2006–2013, respectively. In contrast with climate change, the effects of land‐use changes on the average PWER were much lower, and represented a change in PWER of less than 3.3% across the whole watershed. The study method we used could provide some valuable reference for wind erosion modelling, and the research results should help climate and land‐use researchers to develop strategies to reduce wind erosion. Copyright © 2017 John Wiley & Sons, Ltd.     

Impact of land use changes on catchment soil erosion and sediment yield in the northeastern China: A panel data model application

Land use is an important factor influencing soil erosion and sediment yield (SESY). Regressing soil erosion intensity (SEI) and sediment yield (SY) to land use characteristics can provide necessary information for controlling soil loss. However, current simple regression methods emphasize cross sectional parameters, with less emphasis on temporal variability of relevant land use parameters so that the derived effects of land use change on SESY can be biased. Here, a panel data method was applied to quantify the impact of land use change on SESY in 1954, 1975, and 2015, based on the WaTEM/SEDEM model and seven landscape metrics for 25 reservoir catchments in northeastern China. The results indicate that SEI and area-specific SY (SSY) continuously decreased from 1954 to 2015, which were significantly correlated with landscape metrics such as area-edge metrics of mean patch area (AREA_MN), shape index of the mean related circumscribing circle (CIRCLE_MN), aggregation index of effective mesh size (MESH), patch cohesion index (COHESION), and diversity metrics such as Shannon's diversity index (SHDI), patch richness density (PRD), and modified Simpson's evenness index (MSIEI). The results suggested that catchment SESY can be reduced through decreasing mean patch area, patch mesh size, and physical connectivity of patches, enriching landscape types, and elongating land use patches. These findings are helpful to effectively implement soil conservation measures in northeastern China and similar regions worldwide. The current study also implies that the panel data approach will have beneficial potential applications in earth-science research fields.     

Modeling the sediment yield and the impact of vegetated filters using an event‐based soil erosion model—a case study of a small Canadian watershed

This paper presents the first application of the event‐based MHYDAS‐Erosion model to a small agricultural watershed under temperate climate conditions (Quebec, Canada). Simulation results based on observed and synthetic rainfall events revealed a bimodal behaviour of sediment yield. During high‐intensity rainfall events, most of the sediments reaching the watershed outlet originate from cropland. Meanwhile, during low‐intensity events, most of the sediments come from the drainage network. Furthermore, simulation results show that implementation of 5‐m and 20‐m wide vegetated filters throughout the watershed or at the edge of the most problematic fields (4% of the total fields) could reduce soil loss by 52% and 31%, respectively. The modeling framework could be used for the design and location of beneficial management practices such as grass strips and riparian zones Copyright © 2016 John Wiley & Sons, Ltd.     

Physically-based distributed soil erosion and sediment yield model (DREAM) for simulating individual storm events

Abstract

A relatively simple process-oriented, physically-based distributed (PBD) hydrological model, the distributed runoff and erosion assessment model (DREAM), is described, and a validation study conducted in the semi-forested watershed of Pathri Rao, in the Garhwal Himalayas, India, is reported. DREAM takes account of watershed heterogeneity as reflected by land use, soil type, topography and rainfall, measured in the field or estimated through remote sensing, and generates estimates of runoff and sediment yield in spatial and temporal domains. The model is based on simultaneous solution of flow dynamics, based on kinematic wave theory, followed by solution of soil erosion dynamics. As the storm rainfall proceeds, the process of overland flow generation is dependent on the interception storage and infiltration rates. The components of the soil erosion model have been modified to provide better prediction of sediment flow rates and sediment yields. The validation study conducted to test the performance of the model in simulating soil erosion and sediment yield during different storm events monitored in the study watershed showed that the model outputs are satisfactory. Details of a sensitivity analysis, model calibration and the statistical evaluation of the results obtained are also presented and discussed. It is noteworthy that the distributed nature of the model combined with the use of geographical information system (GIS) techniques permits the computation and representation of the spatial distribution of sediment yield for simulated storm events, and a map of the spatial distribution of sediment yield for a simulated storm event is presented to highlight this capability.

Citation Ramsankaran, R., Kothyari, U.C., Ghosh, S.K., Malcherek, A., and Murugesan, K., 2013. Physically-based distributed soil erosion and sediment yield model (DREAM) for simulating individual storm events. Hydrological Sciences Journal, 58 (4), 872–891.     

Distributed evaluation of the contribution of soil erosion to the sediment yield from a watershed

The correct determination of the sediment yield from a basin is of paramount importance in several hydraulic and environmental applications, such as the evaluation of the storage reduction of artificial reservoirs. However, due to the highly episodic nature of sediment supply and transport in many environments and to the extreme complexity of the processes involved, the evaluation of the sediment load in a river is still highly uncertain. When the time scale of interest is sufficiently long, and when the primary sediment source comes from distributed erosion in the watershed, the problem can be tackled in an indirect fashion, by computing the contribution to the annual suspended yield from soil erosion. In order to accomplish this task, we propose a distributed application of the widely used USLE formula. The formula is automatically applied along drainage networks derived from a digital elevation model and properly modified to take into account the presence of deposition zones in the watershed. © 1997 John Wiley & Sons, Ltd.     

A transport‐distance approach to scaling erosion rates: 3. Evaluating scaling characteristics of Mahleran

In the two previous papers of this series, we demonstrated how a novel approach to erosion modelling (Mahleran – Model for Assessing Hillslope‐Landscape Erosion, Runoff And Nutrients) provided distinct advantages in terms of process representation and explicit scaling characteristics when compared with existing models. A first evaluation furthermore demonstrated the ability of the model to reproduce spatial and temporal patterns of erosion and their particle‐size characteristics on a large rainfall‐simulation plot. In this paper, we carry out a more detailed evaluation of the model using monitored erosion events on plots of different size. The evaluation uses four plots of 21·01, 115·94, 56·84 and 302·19 m², with lengths of 4·12, 14·48, 18·95 and 27·78 m, respectively, on similar soils to the rainfall‐simulation plot, for which runoff and erosion were monitored under natural rainfall. Although the model produces the correct ranking of the magnitude of erosion events, it performs less well in reproducing the absolute values and particle‐size distributions of the eroded sediment. The implications of these results are evaluated in terms of requirements for process understanding and data for parameterization of improved soil‐erosion models. We suggest that there are major weaknesses in the current understanding and data underpinning existing models. Consequently, a more holistic re‐evaluation is required that produces functional relationships for different processes that are mutually consistent, and that have appropriate parameterization data to support their use in a wide range of environmental conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

The responses of hydrological processes and sediment yield to land‐use and climate change in the Be River Catchment,Vietnam

In this study, we investigated the responses of hydrology and sediment yield with impacts of land‐use and climate change scenarios in the Be River Catchment, using the Soil and Water Assessment Tool (SWAT) hydrological model. The calibration and validation results indicated that the SWAT model is a powerful tool for simulating the impact of environmental change on hydrology and sediment yield in this catchment. The hydrologic and sediment yield responses to land‐use and climate changes were simulated based on the calibrated model. The results indicated that a 16.3% decrease in forest land is likely to increase streamflow (0.2 to 0.4%), sediment load (1.8 to 3.0%), and surface runoff (SURQ) (4.8 to 10.7%) and to decrease groundwater discharge (GW_Q) (3.5 to 7.9%). Climate change in the catchment leads to decreases in streamflow (0.7 to 6.9%) and GW_Q (3.0 to 8.4%), increase in evapotranspiration (0.5 to 2.9%), and changes in SURQ (?5.3 to 2.3%) and sediment load (?5.3 to 4.4%). The combined impacts of land‐use and climate changes decrease streamflow (2.0 to 3.9%) and GW_Q (12.3 to 14.0%), increase evapotranspiration (0.7 to 2.8%), SURQ (8.2 to 12.4%), and sediment load (2.0 to 7.9%). In general, the separate impacts of climate and land‐use changes on streamflow, sediment load, and water balance components are offset each other. However, SURQ and some component of subsurface flow are more sensitive to land‐use change than to climate change. Furthermore, the results emphasized water scarcity during the dry season and increased soil erosion during the wet season. Copyright © 2012 John Wiley & Sons, Ltd.     

Inherent relationship of the USLE,RUSLE topographic factor algorithms and its impact on soil erosion modelling

ABSTRACT

The accurate representation of the Earth’s surface plays a vital role in soil erosion modelling. Topography is parameterized in the Universal Soil Loss Equation (USLE) and Revised USLE (RUSLE) by the topographic (LS) factor. For slope gradients of < 20%, soil loss values are similar for both models, but when the gradient is increased, RUSLE estimates are only half of those of USLE. The study aims to assess the validity of this statement for complex hillslope profiles. To that end, both models were applied at eight diverse mountainous sub-watersheds. The USLE and RUSLE indices were estimated utilizing the SEAGIS model and a European dataset, respectively. LS factors were in a 3:1 ratio (i.e. USLE:RUSLE) considering the entire basin area. For areas with slopes <20%, gross erosion estimates of both models converged. Sites of strong relief (>20%) USLE yielded significantly higher values than RUSLE.     

GIS‐based modelling of soil erosion processes using the modified‐MMF (MMMF) model in a large watershed having vast agro‐climatological differences

The present study demonstrates a spatially distributed application of a field‐scale annual soil loss model, the modified‐MMF (MMMF), to a large watershed using hydrological routing techniques, remote sensing data and geospatial technologies. In this study, the MMMF model is implemented after incorporating the corrections suggested in recent literature along with appropriate modifications of the model to suit the agro‐climatological conditions prevailing in most parts of India. Sensitivity analysis carried out through an Average Linear Sensitivity approach indicates that the model outputs are highly sensitive to soil moisture (MS), bulk density (BD), effective hydraulic depth (EHD), ground cover (GC) and settling velocity for clay (VS_c). During calibration and validation, the performance evaluation statistics are mostly in the range of very good to satisfactory for both runoff and soil loss at the watershed outlet. Even spatial validation of the results of intermediate processes in the water phase and the sediment phase, although qualitative, seems to be reasonable and rational. Furthermore, the soil erosion severity analysis for different land‐uses existing in the watershed indicates that about 90% of the watershed area, especially that occupied by agricultural lands, is vulnerable to the long‐term effects of soil erosion. Copyright © 2018 John Wiley & Sons, Ltd.     

A transport‐distance approach to scaling erosion rates: 1. Background and model development

The process basis of existing soil‐erosion models is shown to be ill‐founded. The existing literature builds directly or indirectly on Bennett's (1974) paper, which provided a blueprint for integrated catchment‐scale erosion modelling. Whereas Bennett recognized the inherent assumptions of the approach suggested, subsequent readings of the paper have led to a less critical approach. Most notably, the assumption that sediment movement could be approximated by a continuity equation that related to transport in suspension has produced a series of submodels that assume that all movement occurs in suspension. For commonly occurring conditions on hillslopes, this case is demonstrably untrue both on theoretical grounds and from empirical observations. Elsewhere in the catchment system, it is only partially true, and the extent to which the assumption is reasonable varies both spatially and temporally. A second ground‐breaking paper – that of Foster and Meyer (1972) – was responsible for subsequent uncritical application of a first‐order approximation to deposition based on steady‐state analysis and again a weak empirical basis. We describe in this paper an alternative model (Mahleran – Model for Assessing Hillslope‐Landscape Erosion, Runoff And Nutrients) based upon particle‐travel distance that overcomes existing limitations by incorporating parameterizations of the different detachment and transport mechanisms that occur in water erosion in hillslopes and small catchments. In the second paper in the series, we consider the sensitivity and general behaviour of Mahleran , and test it in relation to data from a large rainfall‐simulation experiment. The third paper of the sequence evaluates the model using data from plots of different sizes in monitored rainfall events. From this evaluation, we consider the scaling characteristics of the current form of Mahleran and suggest that integrated modelling, laboratory and field approaches are required in order to advance the state of the art in soil‐erosion modelling. Copyright © 2008 John Wiley & Sons, Ltd.     

Impact of model simplifications on soil erosion predictions: application of the GLUE methodology to a distributed event‐based model at the hillslope scale

In this paper, we analyse how the performance and calibration of a distributed event‐based soil erosion model at the hillslope scale is affected by different simplifications on the parameterizations used to compute the production of suspended sediment by rainfall and runoff. Six modelling scenarios of different complexity are used to evaluate the temporal variability of the sedimentograph at the outlet of a 60 m long cultivated hillslope. The six scenarios are calibrated within the generalized likelihood uncertainty estimation framework in order to account for parameter uncertainty, and their performance is evaluated against experimental data registered during five storm events. The Nash–Sutcliffe efficiency, percent bias and coverage performance ratios show that the sedimentary response of the hillslope in terms of mass flux of eroded soil can be efficiently captured by a model structure including only two soil erodibility parameters, which control the rainfall and runoff production of suspended sediment. Increasing the number of parameters makes the calibration process more complex without increasing in a noticeable manner the predictive capability of the model. Copyright © 2015 John Wiley & Sons, Ltd.     

A process‐based conversion model for caesium‐137 derived erosion rates on agricultural land: an integrated spatial approach

There is increasing recognition that ¹³⁷Cs data remain one of the few sources of spatially distributed information concerning soil erosion. However, many of the conversion models that have been used to convert ¹³⁷Cs data into soil redistribution rates failed to account for some of the key factors affecting the redistribution of ¹³⁷Cs in agricultural landscapes. The conversion model presented in this paper aims to overcome some of the limitations associated with existing models and therefore to provide more realistic estimates of soil erosion rates on agricultural land. The conversion model aims at coupling soil redistribution processes directly with ¹³⁷Cs redistribution. Emphasis is placed on the spatial representation of soil redistribution processes and the adequate simulation of tillage processes. The benefits of the presented model arise from the two‐dimensional spatial integration of mass balance models with soil erosion models. No a priori assumptions about the intensity of any soil redistribution process are necessary and the level of agreement between observed and simulated ¹³⁷Cs inventories enables us to evaluate the performance of the model. The spatial implementation and the use of fuzzy parameter sets also allow us to assess the uncertainties associated with soil erosion estimates. It was shown that an adequate simulation of tillage processes is necessary and that simplified tillage models may lead to erroneous estimates of soil redistribution. The model was successfully applied to a study site in the Belgian Loam Belt and the results indicated that tillage is the dominant process. Furthermore, the uncertainties associated with the estimation of water erosion rates were much higher than those associated with tillage, especially for depositional areas. Copyright © 2003 John Wiley & Sons, Ltd.     

Modelling the effect of soil burn severity on soil erosion at hillslope scale in the first year following wildfire in NW Spain

Fire severity is recognized as a key factor in explaining post‐fire soil erosion. However, the relationship between soil burn severity and soil loss has not been fully established until now. Sediment availability may also affect the extent of post‐fire soil erosion. The objective of this study was to determine whether soil burn severity, estimated by an operational classification system based on visual indicators, can significantly explain soil loss in the first year after wildfire in shrubland and other areas affected by crown fires in northwest (NW) Spain. An additional aim was to establish indicators of sediment availability for use as explanatory variables for post‐fire soil loss. For these purposes, we measured hillslope‐scale sediment production rates and site characteristics during the first year after wildfire in 15 experimental sites using 65 plots. Sediment yields varied from 0.2 Mg ha^?1 to 50.1 Mg ha^?1 and soil burn severity ranged from low (1.8) to very high (4.5) in the study period. A model that included soil burn severity, annual precipitation and a land use factor (as a surrogate for sediment availability) as explanatory variables reasonably explained the erosion losses measured during the first year after fire. Model validation confirmed the usefulness of this empirical model. The proposed empirical model could be used by forest managers to help evaluate erosion risks and to plan post‐fire stabilization activities. Copyright © 2015 John Wiley & Sons, Ltd.     

Long‐term effects of management practices on water‐driven soil erosion in an intense agricultural sub‐watershed: monitoring and modelling

The overarching objective of this research was to provide an improved understanding of the role of land use and associated management practices on long‐term water‐driven soil erosion in small agricultural watersheds by coupling the established, physically based, distributed parameter Water Erosion Prediction Project (WEPP) model with long‐term hydrologic, land use and soil data. A key step towards achieving this objective was the development of a detailed methodology for model calibration using physical ranges of key governing parameters such as effective hydraulic conductivity, critical hydraulic shear stress and rill/inter‐rill erodibilities. The physical ranges for these governing parameters were obtained based on in situ observations within the South Amana Sub‐Watershed (SASW) (～26 km²) of the Clear Creek, IA watershed where detailed documentation of the different land uses was available for a period of nearly 100 years. A quasi validation of the calibrated model was conducted through long‐term field estimates of water and sediment discharge at the outlet of SASW and also by comparing the results with data reported in the literature for other Iowa watersheds exhibiting similar biogeochemical properties. Once WEPP was verified, ‘thought experiments’ were conducted to test our hypothesis that land use and associated management practices may be the major control of long‐term erosion in small agricultural watersheds such as SASW. Those experiments were performed using the dominant 2‐year crop rotations in the SASW, namely, fall till corn–no till bean (FTC‐NTB), no till bean–spring till corn (NTB‐STC) and no till corn–fall till bean (NTC‐FTB), which comprised approximately 90% of the total acreage in SASW. Results of this study showed that for all crop rotations, a strong correspondence existed between soil erosion rates and high‐magnitude precipitation events during the period of mid‐April and late July, as expected. The magnitude of this correspondence, however, was strongly affected by the crop rotation characteristics, such as canopy/residue cover provided by the crop, and the type and associated timing of tillage. Tillage type (i.e. primary and secondary tillages) affected the roughness of the soil surface and resulted in increases of the rill/inter‐rill erodibilities up to 35% and 300%, respectively. Particularly, the NTC‐FTB crop rotation, being the most intense land use in terms of tillage operations, caused the highest average annual erosion rate within the SASW, yielding quadrupled erosion rates comparatively to NTB‐STC. The impacts of tillage operation were further exacerbated by the timing of the operations in relation to precipitation events. Timing of operations affected the ‘life‐time’ of residue cover and as a result, the degree of protection that residue cover offers against the water action on the soil surface. In the case of NTC‐FTB crop rotation, dense corn residue stayed on the ground for only 40 days, whereas for the other two rotations, corn residue provided a protective layer for nearly 7 months, lessening thus the degree of soil erosion. The cumulative effects of tillage type and timing in conjunction with canopy/residue cover led to the conclusion that land management practices can significantly amplify or deamplify the impact of precipitation on long‐term soil erosion in small agricultural watersheds. Copyright © 2009 John Wiley & Sons, Ltd.