Supported by USA CERL 
developed
with GRASS5.0
Co-Authors:
Matt Hohmann, D. Gebhart, S. Warren (USA CERL), D. Jones (Ft. Hood),
Fred Schrank(NRCS)
TODO;
- prepare the images for linking (photo's, 3D views, maps)
- add the text
- link-in the tutorials for the models
The emphasis on integration of local actions with watershed-scale approaches has a significant impact on the development of supporting GIS and modeling tools. Complex, distributed, physics-based models are needed to improve understanding and prediction of landscape processes at any point in space and time. At the same time, land owners and managers working in the watersheds and fields need fast and easy to use models for which the input data are readily available.
To reflect the need for modeling at different levels of complexity a set of models was developed (Mitas and Mitasova, 1998; Mitasova et al., 1999). The simple models RUSLE3D (Revised Universal Soil Loss Equation for Complex Terrain) and USPED (Unit Stream Power-based Erosion Deposition) are based on modifications of well established equations representing special cases of erosion regimes. The basic empirical parameters for these models are available, however their applicability to a wide range of conditions is limited. The new distributed, process-based model SIMWE (SIMulated Water Erosion) provides capabilities to simulate more complex effects, however both the experimental and theoretical research are still very active and underlying equations, as well as the input parameters,are under continuing development.
This tutorial focuses on the the simpler models with some links and comments on the more complex simulations. The comparison of these models with traditional model results and field observations are in the related document at: modviz/hoodn.html : owl creek and house creek
In the following section we provide a quick reference to models in this
tutorial and on the Internet which are applicable at different scales to
support conservation planning at a hierarchy of land management levels.
We then describe selected models and provide step-by-step instruction on
how to run them in GIS.
|
Scale / unit |
Regional/large watershed
XX sq. miles/km (e.g., installation) |
Landscape/small watershed
XX sq miles/acres/ha (e.g., training area) |
Field /hillslope
XX acres/square m |
| Tasks | assessment of averaged erosion risk
for entire region/installation identification and planning for: |
|
|
| Data | Spatially averaged
|
Distributed
|
Distributed
|
| Processes |
|
|
|
| Models | Spatially averaged
|
Distributed
|
Distributed
|
To keep the tutorial simple and easy to use we focus on the soil detachment, sediment transport and deposition processes while providing links to documents which describe the relevant interacting processes, such as rainfall, infiltration, water flow, vegetation growth, etc.
2.2.1 Erosion processes at multiple scales and related models
Similarly as other landscape processes erosion has multiscale character. Different processes are dominant at different scales and it is therefore important to apply the models at the scales for which they were designed. The scales can range from molecules through raindrops, plots, fields, watersheds, regions to entire continents, however, from the point of view of landuse managment we will discuss the follwing scales
ADD DHI MODELS!!!
a) plot and field scale, resolution 1cm-1m:
At this scale the sheet, rill and gully erosion is distinguished
and should be modeled individually. Rills and gullies are dynamic, evolving
3D features. Spatial variability in land cover (vegetation density, canopy,
stones, roots) are important as well as the human impact such as vehicle
tracks, ditches, ...All conservation measures are represented by their
shape and properties - e.g., contour filter strips, grassways, hedges,
dry dams... the goal of the modeling is detailed assesment, prediction
of different types of erosion and deposition, ....
RillGrow2: Land
Degradation and Rehabilitation Programme, University of Oxford Environmental
Change Institute
EUROSEM
WEPP
SIMWE
b) landscape scale, small watershed, resolution 5m-20m
Govers erosion modeling web site
SedSpec
WEPP on-line
c) regional scale, large watersheds
SWAT
RUSLE/ANSWERS australia
Conservation measures websites (see bookmarks)
Regional scale, large watersheds, resolution 30-100m - stream processes
dominate, spatial variability on hillslopes is averaged-out
2.2.2 Erosion regimes and relevant models
From detachment limited to transport capacity limited and everything in between. LINK movie and images
Special cases:
Deatchment limited - maximum extent of erosion=no deposition, infinite
transport capacity of water flow. Typical for non-agregate clay. Modeled
by USLE, RUSLE3D, .....
Transport capacity limited - maximum extent of deposition, sediment
flow at the transport capacity. Typical for sand. Modeled by USPED, Moore
et al. ....
General:
captures the variability of these regimes as the terrain, water flow,
cover and soil properties change over the landscape. WEPP, SIMWE, CASC2D?,
LISEM???, CHILD
2.2.3 Models
From empirical, spatially averaged towards process-based, distributed.
Process based principles in empirical models (physical representation
of LS factor...)
Erosion, sediment transport and deposition involves complex interactions
between rainfall, surface and subsurface hydrology, soil properties, land
cover and topography. Modeling erosion and deposition in complex terrain
using GIS therefore requires adequate digital elevation model (DEM) as
well as digital data describing spatial distributions of rainfall, soil
and land cover/land use properties.
4.2 Land use/land cover
sources, resolution, level of detail - broad categories at 20-30m
resolution, %vegetation cover for design at sites (1m resolution)
4.3 Soils
4.4 Rainfall
Rainfall - R-factor - annual, monthly, storm
6.1 Continuous value maps - what they mean, legend, color tables (automatic creation of exponential legend with intesity given by parameter p=0.01, colors see Cebecauer/GRASScurvatures for erosion/deposition)
exponential color table for soil detachment (RUSLE3D) in tons/(acre.year) with m=0.6 and n=1.3 (detachment value=exp(n), where n=1,2,3.... and each n has a color associated with it. 0 white : stable 2 light green : low 7 yellow : moderate 20 orange : high 50 red : severe 150 magenta : extreme 500 violet : upper limit
6.2 Class maps - reclassifying the continuous maps, standardized classes. Need for classification for the management purposes
6.3 Sumary statistics, reports: histograms, %area from each class, average rate, total soil detached, total net soil loss, ...
Minimize detachment and net erosion:
model based: set max detachment treshold - create new cover, (necessary C, suggested cover invertly derived from the table), set max net erosion treshold, set elimination of concentrated flow and other criteria
feature based: set buffers along the streams (uniform with given width, adjusted by model,..), set hedge along contour, grass filter strip, conservation area - compute necessary C and adjust shape,
Analyze high risk locations: find roads affected by high erosion risk wetland areas and streams affected by high erosion deposit sediment: increase sedimentation rate in deposition area, create sedimentation pond, ....
Notes - for the management purposes there seems to be a need for
categorization/classification - first streams, land are split into discrete
homogeneous units and then they are classified/zoned for what we can do
with them - is this the most effective approach??? (this results in uniform
buffers, interactions between various landscape phenomena such as streams/topography
ignored, etc. this also results in such observations that we have more
sediment coming from the forested watershed that from agricultural/developed
one.
Plot and field scale, resolution 1cm-1m:
RillGrow2: Land Degradation and Rehabilitation Programme, University of Oxford Environmental Change Institute
WEPP
Landscape scale, small watershed, resolution 5m-20m
general, overviews, summaries:
Watershed management models (relevant are ANSWERS, AGNPS, WEPP, ...:
http://web.aces.uiuc.edu/watershed/model/models_index.htm
Govers erosion modeling web site
SedSpec
WEPP on-line
SWAT
RUSLE/ANSWERS australia
DHI models
Conservation measures websites (see bookmarks)
Regional scale, large watersheds, resolution 30-100m - stream processes dominate, spatial variability on hillslopes is averaged-out
Publications
Bivand Neteler GRASS+R, show impact of integers depending on resolution
Standards
Standardized filed names (e.g. used in ATTAC document) - is there any
official list for that?
Standardized categories for erosion rates severe/high/moderate/low/stable
Standardized color tables for inputs and outputs
Design standard for 3D illustrations maps
the sample maps are at:
Add legends/scale/north to images (create template, write script?)
Predicted erosion map + sites sized and colored according to the observed
sheet /rill erosion
Predicted erosion map + sites sized and colored according to the observed
gully/roaderosion
C-factor map derived from vegetation map + sites colored/labeled according
to observed C-factor
This document describes "field to landscape scale" modeling of selected hydrologic and erosion processes based on representation of input data as multivariate functions (as opposed to homogeneous hillslope segments or subwaterhseds), simulations performed by solution of equations describing relevant physical processes, advanced multidimensional GIS support for storing, processing and visualizing the data and results. The concept, theory and some applications are described in the following papers, proceedings, and reports.
The presented work was supported by the Strategic Environmental Research
and Development Program, USA CERL, Illinois Department of Natural Resources
and C-FAR.
Contacts
Helena Mitasova (GMSLab)
helena@gis.uiuc.edu
Bill Brown (GMSLab) brown@gis.uiuc.edu
Lubos Mitas (NCSA) lmitas@ncsa.uiuc.edu
