The accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways. This paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using TOPMODEL. Distributed moisture status is predicted in TOPMODEL on the basis of spatial indices that depend on flow path definition. The sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients. A strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application.

/pdf/the-prediction-of-hillslope-flow-paths-for-distributed-2fiekephx8.pdf

The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models

The European Soil Erosion Model (EUROSEM) is a dynamic distributed model, able to simulate sediment transport, erosion and deposition over the land surface by rill and interill processes in single storms for both individual fields and small catchments. Model output includes total runoff, total soil loss, the storm hydrograph and storm sediment graph. Compared with other erosion models, EUROSEM has explicit simulation of interill and rill flow; plant cover effects on interception and rainfall energy; rock fragment (stoniness) effects on infiltration, flow velocity and splash erosion; and changes in the shape and size of rill channels as a result of erosion and deposition. The transport capacity of runoff is modelled using relationships based on over 500 experimental observations of shallow surface flows. EUROSEM can be applied to smooth slope planes without rills, rilled surfaces and surfaces with furrows. Examples are given of model output and of the unique capabilities of dynamic erosion modelling in general. © 1998 John Wiley & Sons, Ltd.

https://gruenland.wzw.tum.de/fileadmin/auerswald/1998_Morgan-ESPL.pdf

The European Soil Erosion Model (EUROSEM): A dynamic approach for predicting sediment transport from fields and small catchments.

Soil degradation by accelerated erosion is a serious problem and will remain so during the 21st century, especially in developing countries of the tropics and subtropics. Yet, its extent, severity, and economic and environmental impacts are debatable. Estimates of global and regional land area affected are tentative and subjective. Results of field measurements are often technique-dependent. Considerable progress has been made in modeling soil erosion, yet field validation of these models remains to be done for principal soils and ecoregions. Similar to the land area affected, estimates of erosional impacts on crop yield, productivity and soil quality are tentative and subjective. Further, erosion-induced losses on crop yield are scale-dependent because of the compensatory beneficial effects on yields from depositional sites, and technology-dependent because of the masking effects of input such as fertilizers and irrigation. Erosion caused changes in soil carbon dynamics and non-point source water pollution are important environmental impacts. While erosion (e.g., detachment and transport) can lead to emission of trace gases into the atmosphere, deposition can bury and sequester some of the carbon. In addition to improving the database on the land area affected, there is also a need to assess erosional impacts on productivity and soil C balance at the watershed, regional, and global scale. Copyright © 2001 John Wiley & Sons, Ltd.

http://tinread.usarb.md:8888/jspui/bitstream/123456789/1139/1/soil_degradationRA.pdf

Soil degradation by erosion

Information on sediment and nutrient export from catchments and about related erosive processes is required by catchment managers and decision-makers. Many models exist for the consideration of these processes. However, these models differ greatly in terms of their complexity, their inputs and requirements, the processes they represent and the manner in which these processes are represented, the scale of their intended use and the types of output information they provide. This paper reviews several different erosion and sediment and sediment-associated nutrient transport models with regard to these factors. The review of models is limited to those models with explicit considerations of either the sediment generation or transport process.

A review of erosion and sediment transport models

Few of the infiltration models in current use are suitable for the situation in which the rainfall intensity is initially less than the infiltration capacity of the soil. In this paper a simple two-stage model is developed for infiltration under a constant intensity rainfall into a homogeneous soil with uniform initial moisture content. The first stage predicts the volume of infiltration to the moment at which surface ponding begins. The second stage, which is the Green-Ampt model modified for the infiltration prior to surface saturation, describes the subsequent infiltration behavior. A method for estimating the mean suction of the wetting front is given. Comparison of the model predictions with experimental data and numerical solutions of the Richards equation for several soil types shows excellent agreement.

Modeling infiltration during a steady rain

By adopting two extreme assumptions concerning the behavior of unsaturated soil hydraulic conductivity K near saturation, we derived a two-branched model for ponding time and infiltration rate decay for arbitrary rainfall rates. One assumption was that K varies slowly near saturation and leads to an expression for ponding time and infiltration decay. For initially ponded conditions, ponding time is zero, and with rainfall rate r → ∞, the familiar Green and Ampt (1911) expression results. The other, rather opposite assumption was that K varies rapidly, e.g., exponentially, near saturation. This model also holds for both rainfall and ponded surface conditions, and for ponded conditions the expression is identical to that of Parlange (1971). Each model uses only two parameters, saturated soil conductivity Ks and a parameter that is roughly related to sorptivity and responds nearly linearly to variations in initial saturation. Both parameters are physically related to measurable soil properties. Methods are presented to estimate parameters of either model from infiltrometer tests. The two models are compared with a precise numerical solution of the unsaturated soil water diffusion equations for three soils that represent a range of soil behaviors near saturation. Our results show that either assumption would be an excellent model for most hydrologic purposes, and the relative goodness of fit of each model is generally consistent with the appropriate behavior of K(θ → θS).

A parameter‐efficient hydrologic infiltration model

KINEROS : a kinematic runoff and erosion model : documentation and user manual

KINEROS - a kinematic runoff and erosion model

A new infiltration equation is obtained by introducing a new parameter, in addition to the usual sorptivity and conductivity at saturation. This third parameter can be related to the conductivity of the soil. In particular, if this parameter is equal to zero, then the infiltration equation r

Roger E. Smith

Papers

The European Soil Erosion Model (EUROSEM): A dynamic approach for predicting sediment transport from fields and small catchments.

A parameter‐efficient hydrologic infiltration model

KINEROS : a kinematic runoff and erosion model : documentation and user manual

KINEROS - a kinematic runoff and erosion model

The Three-Parameter Infiltration Equation