Advanced Terrain Analysis Concepts n Specific Catchment Area n The D  Surface Flow Model n Topmodel u Terrain based calculations of saturated areas and soil moisture deficit n Generalized flow accumulation functions u Flow algebra n Extending ArcGIS u Scripts and Programming

Drainage area can be concentrated or dispersed (specific catchment area) representing concentrated or dispersed flow.

Specific catchment area a is the upslope area per unit contour length [m 2 /m  m] Upslope contributing area a Stream line Contour line

The D  Algorithm Tarboton, D. G., (1997), "A New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models," Water Resources Research, 33(2): ) (

Contributing Area using D8 Contributing Area using D 

TOPMODEL Beven, K., R. Lamb, P. Quinn, R. Romanowicz and J. Freer, (1995), "TOPMODEL," Chapter 18 in Computer Models of Watershed Hydrology, Edited by V. P. Singh, Water Resources Publications, Highlands Ranch, Colorado, p “TOPMODEL is not a hydrological modeling package. It is rather a set of conceptual tools that can be used to reproduce the hydrological behaviour of catchments in a distributed or semi- distributed way, in particular the dynamics of surface or subsurface contributing areas.”

Hydrological processes within a catchment are complex, involving: Macropores Heterogeneity Fingering flow Local pockets of saturation The general tendency of water to flow downhill is however subject to macroscale conceptualization

Map of saturated areas showing expansion during a single rainstorm. The solid black shows the saturated area at the beginning of the rain; the lightly shaded area is saturated by the end of the storm and is the area over which the water table had risen to the ground surface. [from Dunne and Leopold, 1978] Seasonal variation in pre-storm saturated area [from Dunne and Leopold, 1978]

TOPMODEL Key Ideas Surface saturation and soil moisture deficits based on topography –Slope –Specific Catchment Area –Topographic Convergence Partial contributing area concept Saturation from below (Dunne) runoff generation mechanism

Topmodel - Assumptions Specific catchment area a [m 2 /m  m] (per unit contour length) tan  The soil profile at each point has a finite capacity to transport water laterally downslope based on slope and transmissivity, q cap =T tan . The actual lateral discharge is proportional to specific catchment area, q=Ra Relative wetness at a point and depth to water table is determined by comparing q and q cap The dynamics of the saturated zone can be approximated by successive steady state representations involving the depth to water table adjusting to accommodate q that results in expansion and contraction of the variable source area contributing to saturation excess runoff VSA

Slope Specific Catchment Area Wetness Index ln(a/tan  ) from Raster Calculator. Average, = 6.9 TOPMODEL and GIS

Numerical Example Given K o =10 m/hr f=5 m -1 Q b = 0.8 m 3 /s a (from GIS) n e = 0.2 Raster calculator -( [ln(sca/S)] - 6.9)/ Compute R= m/h =6.9 T=2 m 2 /hr

Generalized Flow Accumulation

Useful for example to track where sediment or contaminant moves

Useful for example to track where a contaminant may come from

Useful for a tracking contaminant or compound subject to decay or attenuation

Useful for a tracking a contaminant released or partitioned to flow at a fixed threshold concentration

Transport limited accumulation Useful for modeling erosion and sediment delivery, the spatial dependence of sediment delivery ratio and contaminant that adheres to sediment

Reverse Accumulation Useful for destabilization sensitivity in landslide hazard assessment with Bob Pack

Extending ArcGIS via programming n Why Programming u Automation of repetitive tasks u Implementation of functionality not available n Programming functionality u Scripts (AML, VB, Python, Avenue) u Interfaces for application programmers u Model Builder u ArcObjects u COM Integration

Geodatabase view: Structured data sets that represent geographic information in terms of a generic GIS data model. Geovisualization view: A GIS is a set of intelligent maps and other views that shows features and feature relationships on the earth's surface. "Windows into the database" to support queries, analysis, and editing of the information. Geoprocessing view: Information transformation tools that derives new geographic data sets from existing data sets. Three Views of GIS adapted from

Examples TauDEM – ArcMap toolbar using Visual Basic/C++ (implementation of functionality not available in ArcGIS) Visual Basic Programming of simple grid calculations

TauDEM Software Functionality n Pit removal (standard flooding approach) n Flow directions and slope u D8 (standard) u D  (Tarboton, 1997, WRR 33(2):309) u Flat routing (Garbrecht and Martz, 1997, JOH 193:204) n Drainage area (D8 and D  ) n Network and watershed delineation u Support area threshold/channel maintenance coefficient (Standard) u Combined area-slope threshold (Montgomery and Dietrich, 1992, Science, 255:826) u Local curvature based (using Peuker and Douglas, 1975, Comput. Graphics Image Proc. 4:375) n Threshold/drainage density selection by stream drop analysis (Tarboton et al., 1991, Hyd. Proc. 5(1):81) n Wetness index and distance to streams n Water Quality Functions

TauDEM in ArcGIS ESRI binary grid ASCII text grid ESRI gridio API (Spatial analyst) Data Access libraries (grid, shape, image, dbf) TauDEM C++ library Fortran (legacy) components Standalone command line applications C++ COM DLL interface Visual Basic MapWindow plugin Visual Basic ESRI ArcGIS 8.x+9.x Toolbar Vector shape files Data formats Available from Binary direct access grid

Implementation Details Spatial Analyst includes a C programming API (Application Programming Interface) that allows you to read and write ESRI grid data sets directly. Excerpt from gioapi.h / * GetWindowCell - Get a cell within the window for a layer, * Client must interpret the type of the output 32 Bit Ptr * to be the type of the layer being read from. * * PutWindowCell - Put a cell within the window for a layer. * Client must ensure that the type of the input 32 Bit Ptr * is the type of the layer being read from. * */ int GetWindowCell(int channel, int rescol, int resrow, CELLTYPE *cell); int PutWindowCell(int channel, int col, int row, CELLTYPE cell);

STDMETHODIMP CtkTauDEM::Areadinf(BSTR angfile, BSTR scafile, long x, long y, int doall, BSTR wfile, int usew, int contcheck, long *result) { USES_CONVERSION; //needed to convert from BSTR to Char* or String *result = area( OLE2A(angfile), OLE2A(scafile), x,y,doall, OLE2A(wfile), usew, contcheck); return S_OK; } C++ COM Methods used to implement functionality using Microsoft Visual C++

Visual Basic for the GUI and ArcGIS linkage Private TarDEM As New tkTauDEM … Private Function runareadinf(Optional toadd As Boolean = False) As Boolean Dim i As Long runareadinf = False i = TarDEM.Areadinf(tdfiles.ang, tdfiles.sca, 0, 0, 1, "", 0, 1) If TDerror(i) Then Exit Function If toadd Then AddMap tdfiles.sca, 8 End If runareadinf = True End Function

Visual Basic Programming in ArcMAP References ESRI, (1999), ArcObjects Developers Guide: ArcInfo 8, ESRI Press, Redlands, California. Zeiler, M., (2001), Exploring ArcObjects. Vol 1. Applications and Cartography. Vol 2. Geographic Data Management, ESRI, Redlands, CA.

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