SIBERIA 8.30 Manual - Telluric Researc h .SIBERIA is a computer model for simulating the evolution

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  • User Manual for SIBERIA(Version 8.30)

    Prof. Garry WillgooseTelluric Research,100 Barton Street,Scone, NSW, 2337

    AUSTRALIA.Email: g.r.willgoose@leeds.ac.uk

    July 2005, Garry Willgoose,Telluric Research

  • 1 Introduction .......................................................................................... 12 Background. ......................................................................................... 2

    2.1 SIBERIA................................................................................... 22.2 Tectonic uplift........................................................................... 62.3 Erosion processes...................................................................... 72.4 Runoff models .......................................................................... 92.5 Channel models ........................................................................ 102.6 Internal numerics ...................................................................... 12

    3 Running SIBERIA................................................................................ 143.1 Running the program................................................................ 143.2 SIBERIA parameters. ............................................................... 213.3 File formats............................................................................... 343.4 Controlling the Operation of SIBERIA.................................... 42

    4 SIBERIA Extended Models ................................................................. 534.1 General comments about SIBERIA Extended Models............. 534.2 The Built-in Erosion Models .................................................... 544.3 The Built-in Runoff Models ..................................................... 594.4 The Built-in Tectonics Models ................................................. 624.5 The Built-in Drainage Directions and Contour Banks Models 634.6 The Built-in Channel Models ................................................... 644.7 The Built-in Soil Models .......................................................... 654.8 The Generic Dependent Model................................................. 654.9 The Built-in Layers Models...................................................... 66

    5 Monte-Carlo Modelling........................................................................ 776 Calibration of SIBERIA....................................................................... 78

    6.1 Calibration to erosion plot data................................................. 786.2 Calibration to other erosion models.......................................... 85

    7 REFERENCES..................................................................................... 88APPENDICES.................................................................................................. 91

    Appendix A: Revision History............................................................. 91Appendix B: Code to read in restart files. ............................................ 93Appendix C: Code to read in boundary files

    104Appendix D: Shell program to analyse RST and BND file formats

    107

  • SIBERIA 8.30 User Manual 1

    1 Introduction

    This manual describes how to use the catchment evolution model SIBERIA developed by theauthor, beginning in 1986. SIBERIA is a computer model for simulating the evolution oflandscapes under the action of runoff and erosion over long times scales (typically more than afew years). SIBERIA is both a very simple model and a very sophisticated one. The hydrologyand erosion models are based on ones that are simple and widely accepted in the hydrology andagricultural communities since the 1960s. These models are based on widely accepted physicsand have been successfully calibrated in a range of environments. The sophistication ofSIBERIA lies in (1) its use of digital terrain maps for the determination of drainage areas andgeomorphology and (2) its ability to efficiently adjust the landform with time in response to theerosion that occurs on it.

    The basic theory underlying the model and the approximations required forcomputer solution are described in this manual. The parameters that the models uses aredescribed together with the process involved in running SIBERIA. The standard file formatsused for input to the model and for transfer to other data analysis and visualisation packages aredescribed and sample code is provided for input of these files. Finally, details are provided onthe standard procedures that are available in the model to extend various components of themodel if the standard ones should fail to meet the purposes of the user.

    For further information about the details of the theory underlying SIBERIA orresults from the model the publications in the references should be consulted.

    1.1 A Warning to US Users on Model Units

    When the physical units option (ModeErode20 and ModeRunoff20) is selectedfor SIBERIA the units assumed are SI. Briefly: Vertical elevation and horizontal distance units: metres Sediment discharge units: cubic metres of sediment/metre width/timestep (note that cubic

    metres here is the number of cubic metres of sediment that would consumed by depositedsediment equivalent to bulk density - NOT the volume consumed by the sedimentparticles alone equivalent particle density)

    Timestep units: Normally they are considered as years in EAMS but all flux parameters aredefined per timestep

    Bulk Density units: metric tonnes/cubic metre Grid Spacing: metres

    There are no options in SIBERIA to work in imperial units so that all problems needto be converted to metric units.

  • SIBERIA 8.30 User Manual 2

    2 Background.

    2.1 SIBERIA

    What follows is a description of the philosophy and methodology used by SIBERIA. Greaterdetail can be found in Willgoose, et al. (1989, 1991a-d, 1994), Willgoose (1993, 1994a,b) andWillgoose and Riley (1993, 1998a,b).

    The flood response of a catchment to rainfall is dependent on the geomorphic formof the catchment. But the catchment runoff not only responds to catchment form, it also shapesit through the erosion processes that act during runoff events. Over geologic time the catchmentform, shaped by the range of erosion events, reflects the runoff processes that occur within it.The channel network form and extent reflect the characteristics of both the hillslope andchannel processes. Hydrologists have long parameterised the influence of the geomorphologyon flood response (e.g., Rodriguez-Iturbe and Valdes, 1979). Geomorphologists have largelyfitted statistics to the landscape ignoring the historic processes that created the landscape(Strahler, 1964; Shreve, 1966) though there have been some notable exceptions to thisgeneralisation (Gilbert, 1909; Horton, 1945). The difficulty of the problem is such that thenumber of researchers that have attempted to unify the geomorphology and the hydrology issmall (Kirkby, 1971; Dunne, 1989; Huggett, 1988), even though the importance of bothspecialisations has long been recognised by geomorphologists:

    "to look upon the landscape ... without any recognition of the labor expended inproducing it, or of the extraordinary adjustments of streams to structures and ofwaste to weather, is like visiting Rome in the ignorant belief that the Romans oftoday have no ancestors." (page 268, Davis, 1954)

    The main stumbling blocks to the fulfillment of the promise of this scientificparadigm have been the range of temporal scales (geologic versus flood event timescales) andspatial scales (catchment and channel length scales) that are important in the problem; theheterogeneity in both space and time of the dominant processes; and the problem of theunification and observation of the processes acting at these disparate scales. Physically basedcomputer models of catchment development (e.g., Ahnert, 1976; Kirkby, 1987) are importanttools in the understanding of the interactions between hydrologic process and response,primarily because of their ability to explore the sensitivity of the system to changes in thephysical conditions, without many of the difficulties of identification and generalisationassociated with the heterogeneity encountered in field studies.

    The ultimate goal is to develop a quantitative understanding of how channelnetworks and hillslopes evolve with time using a computer model of landscape evolution.Catchment form and hydrologic response will then be seen in the context of the completehistory of erosion development of the catchment.

  • SIBERIA 8.30 User Manual 3

    A large scale model of catchment evolution (SIBERIA) involving channel networkgrowth and elevation evolution is documented below. This model integrates a model of erosionprocesses, theoretically and experimentally verified at small scales, with a physically basedconceptualisation of the channel growth process. Neither the properties of the channel networknor the properties of the hillslopes can be viewed in isolation. They must be viewed ascomponents of a complicated large scale non linear system: the drainage basin. The basic tenetof this work is that it is necessary to understand the physics of the catchment processes to beable to fully understand the catchment form and that it is necessary to " ... identify linkedprocess equations and so define geomorphic systems in such a way that an analytical, predictiveapproach can be used ..." (p. 48, Huggett, 1988). It is not claimed, nor is it intended, that themodel presented below account for all the processes occurring in the catchment. Rather ageneral model framework is presented which is both physically realistic and incorporates thedominant physical processes and which provides a useful tool for the study of the importantinteractions within the catchment. It is, however,