The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Chen, Jun

Bibliographic data

Monograph

Persistent identifier:: 856566209

Author:: Chen, Jun

Title:: The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Sub title:: May 23 - 25, 2001, Bangkok, Thailand

Scope:: VI, 434 Seiten

Year of publication:: 2001

Place of publication:: Pathumthani, Thailand

Publisher of the original:: AIT

Identifier (digital):: 856566209

Illustration:: Illustrationen, Diagramme, Karten

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: MODELING LAND USE EFFECT ON URBAN STORM RUNOFF AT THE WATERSHED SCALE. Chansheng HE

Document type:: Monograph

Structure type:: Chapter

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 129 remaining at the cell outlet (USDA ARS 1995). Through the routing function, AGNPS links the upland erosion, sediment, and nutrients (N, P, and COD) with the downstream water quality. This feature allows the examination of amount of sediments and nutrients either for the entire watershed (measured at the watershed outlet) or on a cell by cell basis. By comparing runoff estimates from individual cells, problem areas within the watershed can be identified for targeting the best management practices (He et al. 1993). AGNPS requires 22 input parameters. These include: (1) cell number, (2) cell division, (3) receiving cell number, (4) receiving cell division, (5) flow direction, (6) SCS curve number, (7) land slope, (8) slope shape, (9) field slope length, (10) overland Manning’s roughness coefficient, (11) soil erodibility (K) factor, (12) cropping management (C) factor, (13) support practice (P) factor, (14) surface condition constant (adjustments for the time it takes channelization of overland runoff), (15) chemical oxygen demand, (16) soil texture, (17) fertilizer indicator, (18) pesticide indicator, (19) point source indicator, (20) additional erosion indicator, (21) impoundment indicator (number of ponds in the impoundment terrace system), and (22) channel indicator (indication of the number of channels in the cell) (USDA ARS 1995). As AGNPS operates on a cell basis, each cell, when considered separately represents 22 layers of input data. Output of AGNPS includes estimates of surface runoff volume (inches), peak flow rate (in cfs), sediment yield (tons), mass of sediment attached and soluble N in runoff (Ibs/acre), mass of sediment attached and soluble P in runoff (Ibs/acre), and soluble chemical oxygen demand (Ibs/acre). These results can be viewed in either tabular or map format for examination of critical runoff, sediment, and nutrient loading areas. 2.2 Development of ArcView-AGNPS Interface Analysis of nonpoint source pollution in an agricultural watershed by AGNPS involves providing 22 input parameters for each of the cells that represent the entire watershed, which is often a tedious and time-consuming task. To address this issue, a number of GIS-AGNPS interfaces have been developed such as GRASS-AGNPS (Engel et al., 1993; He et al., 1993; and Line et al., 1997) and Arc/Info-AGNPS (Liao and Tim, 1997). Those interfaces operate in UNIX environment. In this study, we develop ArcView Nonpoint Source Modeling (AVNPSM), a WINDOWS-based interface to integrate the AGNPS with ArcView (Version 3.0a or later versions) Spatial Analyst and AGNPS using Avenue (a programming language for ArcView) scripts (He et al. 2001). The basic databases required for the AVNPSM include: soil database, digital elevation, land use/cover, water features such as watershed boundary and course of streamflow, climate, and crop management information. A soil database such as STATSGO (State Soil Geographic Data Base) is used to extract information on soil texture, hydrologic group, and soil erodibility factor (K). A digital elevation model (DEM) is used to derive slope, slope length, aspect, and other related parameters. Land use/cover file is used to determine SCS curve number and management factors such as crop management (C), fertilization , and support practice (P ), etc. The water feature database is used to help create the watershed coverage and process and edit the flow direction file. Climate data (storm events) are used to calculate surface runoff and soil erosion in the AGNPS model. Management information includes crop types and rotation, fertilization level, and tillage practices. These files need to be processed to either an Arc/Info coverage or ArcView shape format to be compatible with the format requirement of the AVNPSM interface. Once the input files are ready, the interface can generate the required AGNPS parameters (Parameter Generator), create an AGNPS input file (Input Processor), display the simulated AGNPS output (Output Visualizer), and conduct statistical analysis such as central tendency and analysis of variance (Statistical Analyzer). These components of the interface are discussed separately below: Parameter Generator. The AVNPSM, developed using ArcView Avenue scripts (ESRI, Inc., 1996), provides a pull-down menu to generate the required parameters. As shown in Fig. 1, a user first needs to set global variables, that is, giving the name and location of the basic GIS layers: soil, DEM, land use/cover, and water features (watershed boundary). The user can then list these global files to ensure they are set correctly. Once this is done, the user can follow the pull-down menu to generate each parameter sequentially. During the FISHNET (file name for dividing the study watershed into grids based on the watershed boundary database) creation (in the AGNPS Utility module), the user can determine the number of grids (cells) in a watershed either by grid size or by number of cells. The interface will create a grid file covering the entire watershed. For topographically related parameters (from Flow Direction to Slope Shape), the interface uses some of the ArcView Spatial Analyst built-in functions (Flow Accumulation, Flow Direction, Slope, Aspect) to extract those parameters. The Flow Direction, once created, needs to be carefully edited to remove any loops in the file, i.e. circles of flow involving several adjacent cells in the file. Those loops need to be removed. A separate pull-down menu is created to facilitate this process. The user can go to AGNPS Utility module to edit the flow direction either by one cell at a time or several cells at a time. The K-factor (soil erodibility) and soil texture are generated from the soil database such as the STATSGO or digitized soil maps. The soil texture includes 4 classes: sand, clay, loam, and peat or water. Values for the K factor are derived from STATSGO corresponding to the soil texture. The land use/cover related parameters such as SCS Curve Number, Manning's coefficients, C factor, fertilizer and pesticide application etc. can be entered either by land cover category or by block of cells. The information for these parameters comes from agricultural statistics, literature, and soil and water conservation district personnel Input File Processor. Once all the 22 parameters are generated, the user can go to the File Processor module to develop an input file for AGNPS model. The file is in ASCII format and compatible with AGNPS input format requirement. Model Executor. AGNPS model execution is done either within Windows or separately in the simulated DOS mode. Depending on the number of grids in the input file, model execution takes no more than a couple minutes. Output Visualizer. The simulated AGNPS results of hydrology, sediment, and nutrients can be viewed either in tabular or in map format. Users can select any variable from the output file and display it in ArcView for analysis of spatial pattern using the Output Visualizer. Statistical Analyzer. Many current GIS packages have limited statistical capabilities (Steyaert and Goodchild 1994). Although able to perform central tendency analysis such as mean and standard deviation, the ArcView GIS (Version 3.1) lacks other statistical functions. The AVNPSM interface adds the ANOVA (analysis of variance) function to the ArcView and enables a user to examine the relationships of land use/cover and simulated results of hydrology, sediment, and nutrients. Land Use Change Simulator. A land use change icon (P icon) in the AVNPSM interface allows a user to specify land use change scenario in a sub-basin or specific area based on the land use/cover file and evaluate the hydrologic impact of this change to the downstream area.

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