Erosion and deposition modelling within Arc/Info
Best Wishes to you the visitor
Acknowledgement
Background information
What is TBGIS?
What you need to run TBGIS?
What you can do with TBGIS?
List of some features about TBGIS?
Application of TBGIS on a UK field
Acknowledgement
This work can not be completed without the generous help from enthusiatic activists
on ESRI-L. I whole-heartly recommend ESRI-L to everyone who want to fully exploite the
potential of Arc/Info GIS. I also owe a lot to Dr. R. Ashmore for bringing up my
interest on Arc/Info GIS and providing easy acess to huge volumes of relevant documentation.
Since this is part of my Ph.D project, thanks are also due to Prof. D. E. Walling and Dr. T. A. Quine.
Background Information
Though various data structures have been used in hydrologic and erosion and deposition modelling, uniformed cell size (or raster-based) is still the most popular one. This data structure is also adopted in many GIS systems.
Terrain modeling has almost become intergral part of every raster-based GIS systems. One of the latest advance is
the extraction of spatially-distributed and hydrological, ecological, geomorphological significant terrain attributes.
The demonstration of GRASS GIS in terrain modelling and erosion and deposition simulation as well as hydrological modelling have well-illustrated this
point. As terrain has important role in most surface processes, availability of those terrain attributes has boosted
the intergration of GIS and distributed modelling. several distributed erosion models has been integrated with GRASS
GIS.
Though most GIS systems claim strong capacity in data intergration and management, cartographic mapping, and spatial modelling, following
problems has impeded the wide application of GIS:
- Lack of site-specific data
- Uncertainty associated with data quality and difficult in data quality assessment
- Command-driven interface make them user-unfriendly
- Slow learning curve
- Some functions give unrealistic results. They remain to be tested and improved
Topography is the most widely available data and it may play a dominant role in some surface processes.
Terrain-based modeling approach has already been used to simulate hydrological response, estimate erosion and deposition potential, potential evapotranspiration, etc.
Having realized the problems associated with existing algorithms in extracting terrain attributes from digital terrain data, new methods are being developed. Two programs are most interesting:
- GRIDATB program: As part of TOPMODEL distribution programs, it is used to derive a distribution of ln(a/tanB) values from a regular raster grid of elevations for any catchment or subcatchment using
the multiple direction flow algorithm of Quinn et al(1991). FORTRAN source codes are provided.
- TAPES-G program:As fas as I knew, this unix-based program is the most versatile and comprehensive terrain analysis program so far. Different options are provided for determining flow direction (D8, Rho8, or Frho8), flow accumulation (D8, multiple flow paths, and Costa-Cabral'method),
and slope gradient (D8 or Finite Difference).Other related programs in the bundle include DYNWET for calculating wetness index, EROS for soil loss and erosion and deposition potential, SRAD for estimating solar radiation. You can refer to its homepage
for general information and to download software and email Dr. John Gallant for technical queries. Codes to transfer data and results to and from the Arc/INfo software has been developed by Dr. John P. Wilson
What is TBGIS?
TBGIS is an intuitive, menu-driven terrain analysis and modeling tool based on Arc/Info GIS. AML(Arc/Info Macro Language), form menu, and dozens of C executable programs are combined to intergrate existing surface generation and hydrological modelling functions, develop new tools, and make Arc/Info GIS much friendly. All file are packed and compressed
into one file and shell scripts are provided to install and de-install the program. For users, you only have to fill the form and click the buttons. Then, work will be done.
What you need to run TBGIS
TBGIS is based on workstation Arc/Info GIS at version 7.x. It is residented in GRID module. But refer to ARC, TABLE, ARCPLOT, TIN modules. To make full use of TBGIS, you should have acess to those modules. Since it is a menu-driven program, a mouse is essential.
What you can do with TBGIS?
Functions of TBGIS can be grouped as:
DEM generation from various sources
DEM quality examination
Calculation of terrain-controlled erosion potential
Estimation of relative erosion and deposition
Transformation of relative erosion and deposition to caesium-137 inventory at sampling time
Data managent, analysis, visualization, and export
You can play with a clickable menu to get an idea that how TBGIS works.
List of some features about TBGIS?
Following features are picked out by me:
Application of TBGIS on a UK field
TBGIS has been applied on a cultivated field near Crediton, Exeter. It has representative topography and been under cultivation before 1950s. Apart from detail topographic mapping, regularly distributed soil samples for caesium-137 detection has also been taken.
The distribution of caesium-137 inventory is compared with predicted patterns of relative erosion and deposition pattern from tillage erosion and water erosion with multiple flow paths to infer dominant soil redistribution process. Predicted patterns are more realistic than those from traditional D8 method.
