logo资料库

hec-geohms前期处理.pdf

发布时间：2022-06-01 发布人：admin 分类：说明书 资料大小：0.54M 资料格式：pdf 举报 版权申诉
第1页 / 共15页
第2页 / 共15页
第3页 / 共15页
第4页 / 共15页
第5页 / 共15页
第6页 / 共15页
第7页 / 共15页
第8页 / 共15页
资料共15页，剩余部分请下载后查看
    Creating SCS Curve Number Grid using HEC-GeoHMS Prepared by Venkatesh Merwade School of Civil Engineering, Purdue University vmerwade@purdue.edu October 2010 Introduction SCS curve number grid is used by many hydrologic models to extract the curve number for watersheds. The objective of this tutorial is to use soil and land use data to create a curve number grid using HEC-GeoHMS (ArcGIS 9.2 version). Computer Requirements You must have a computer with latest windows operating system, and the following programs installed: 1. ArcGIS 9.3 (with ArcInfo) 2. Arc Hydro tools (latest version) 3. Hec-GeoHMS for ArcGIS 9.3 (latest version) Make sure the Arc Hydro tools (version that works with 9.2) are installed on the system. There are lots of Arc Hydro tools available on the internet. The version that is used in this tutorial including installation instructions is available at the following link. ftp://ftp.ecn.purdue.edu/vmerwade/download/data/tools.zip The HEC-GeoHMS set-up file for this tutorial is also included in this above tools.zip file. Just unzip the file, and run the setup to install both ArcHydro and HEC-GeoHMS. You will need to have administrative access to install Arc Hydro and HEC-GeoHMS. Data Requirements and Description This tutorial requires the following datasets: (1) DEM for the study area (2) SSURGO soil data (3) 2001 land cover grid from USGS The DEM and land cover grid from USGS and SSURGO data for Cedar Creek in northeast Indiana are provided as zip file at the end of this paragraph. The SSURGO soil data that will be used is provided in a geodatabase (cedar_ssurgo.mdb) that is created in the “Downloading SSURGO Soil Data” tutorial available at: (http://web.ics.purdue.edu/~vmerwade/education/download_ssurgo.pdf). You can look at the SSURGO download tutorial if you want to learn how this dataset is processed. Also, if you are 1
    interested in downloading the DEM and land cover data by yourself, instructions are available in the following tutorial: http://web.ics.purdue.edu/~vmerwade/education/ned_nhd.pdf It is highly recommended that you go through these exercises of downloading the data to make yourself aware of the procedure involved. (Notes: 1. The DEM, land use and soil data used in this tutorial are already clipped to the Cedar Creek study watershed 2. This tutorial uses the SSURGO soil data, which is the highest resolution soil data available in public domain from NRCS. This can be replaced by STATSGO data as long as you know how to interpret STATSTO to follow the steps provided in this tutorial) Download the data from ftp://ftp.ecn.purdue.edu/vmerwade/download/data/cngrid.zip Unzip cngrid.zip in your working directory. The ArcCatalog-view of the data folder (or whatever name you gave to your working folder) is shown below: cedar_ssurgo is the geodatabase with SSURGO spatial and tabular data for cedar creek area. cedar_dem is the raw 30 DEM for Cedar Creek obtained from USGS and clipped for the study watershed, and cedar_lu is the 2001 land cover grid from USGS. All datasets have a common spatial reference (NAD_1983_UTM_16). Note: It is very critical to assign and use consistent coordinate system for all the datasets. Getting Started Open ArcMap. Create a new empty map, and save it as cngrid.mxd (or any other name). Right click on the menu bar to pop up the context menu showing available tools as shown below. 2
    Check the Arc Hydro Tools 9 menu. If the Arc Hydro Tools menu does not appear in the list, click on Customize (Scroll down the list to see “Customize”). In the Customize dialog that appears, check the Arc Hydro Tools box. You should now see the Arc Hydro tools added to ArcMap as shown below. You can leave it floating or you may dock it in ArcMap menubars. Similarly add Spatial Analyst extension and activate it by clicking on ToolsExtensions…, and checking the box next to Spatial Analyst. Dataset Setup All raster data created with the Arc Hydro are stored in a subdirectory with the same name as the dataset or Data Frame in the ArcMap document (called Layers by default and under the directory where the project is stored). The location of the vector, raster, and time series data can be explicitly specified using the function ApUtilitiesSet Target Locations. 3
    You can leave the default settings if they are pointing to the same directory where the ArcMap document is saved. Now load data in the map document. Click on the Add icon raster data. In the dialog box, navigate to the location of the data; select cedar_dem raster file containing the DEM for Cedar creek and click on the Add button. Save the map document. to add the Fill Sinks (Note: If you have results from the terrain processing tutorial, you can use the Fil DEM from the exercise directly skipping this step. Go to next section on preparing landuse data) The first step in creating a curve number grid is to “hydrologically correct” the raw DEM by filling sinks. The Fill Sinks function in Arc Hydro fills the sinks in a grid. If cells with higher elevation surround a cell, the water is trapped in that cell and cannot flow. The Fill Sinks function modifies the elevation value to eliminate these problems. On the ArcHydro Toolbar, select Terrain PreprocessingData ManipulationFill Sinks. Confirm that the input for DEM is cedar_DEM. The output is the Hydro DEM layer, named by default Fil. This default name can be overwritten. Leave the other options unchanged. 4
    Press OK. Upon successful completion of the process, the HydroDEM (in older ArcHydro, this is called Fil) layer is added to the map. This process takes a few minutes. Save the map document. Preparing land use data for CN Grid Add cedar_lu grid to the map document. You will see the grid is added with a unique symbology assigned to cells having identical numbers as shown below: 5
    These numbers represent a land use class defined according to the USGS land cover institute (LCI). A description of some of the land classes and their associated numbers in the grid is shown below by reproducing LCI webpage (http://landcover.usgs.gov/classes.php). You can visit LCI website (publications link) to learn more about how the land use grid is created. Eventually, we are going to use these land use classes and soil group type, in conjunction with SCS curve numbers, to create the curve number grid. The SCS CN table gives CN for different combinations of land use and soil group. The cedar_lu grid has 15 different categories which you can leave unchanged, or reclassify the grid to reduce the number of land use classes to make the task easier. If you open the attribute table of cedar_lu, you will see that majority of cells represent grass/crops, followed by forest, developed land, and then water. We will reclassify cedar_lu to represent these four major classes. The following table shows how we will accomplish the reclassification of cedar_lu (you are free to have more or less classes). 6
    Original NLCD classification Revised classification (re- Description classification) Number 1 Description Water Number 11 90 95 2 3 Medium Residential Open water Woody wetlands Emergent herbaceous wetlands Developed, open space Developed, low intensity Developed, medium intensity Developed, high intensity Deciduous forest Evergreen forest Mixed forest Barren land Shrub/scub Grassland/herbaceous Pasture/hay Cultivated crops 21 22 23 24 41 42 43 31 52 71 81 82 To implement the above re-classification, use the Spatial Analyst Toolbar in ArcMap. If Spatial Analyst is not visible in the menu bar, activate it in the same way you activated the Arc Hydro toolbar. Click on Spatial AnalystReclassify…. In the reclassification window, confirm the Input raster is cedar_lu, Reclass field is Value, and then manually assign the new numbers based on the above table as shown below (leave NoData unchanged). Agricultural 4 Forest 7
    Save the output raster as lu_reclass in your working folder, and click OK. A new grid named lu_reclass will be added to the map as shown below (you may not get the same colors in symbology which is OK) The final step in processing land use data is converting the reclassified land use grid into a polygon feature class which will be merged with soil data later. Click on Spatial AnalystConvertRaster to Features.. Confirm the Input raster is lu_reclass, the Field is Value, output geometry type is Polygon, and save the Output features as landuse_poly.shp in your working directory (this output is saved only as a shapefile without any other options). Click OK. 8
    分享到：
    赞 收藏

    相关推荐

    资料库

    行业

    共收录7266份资料，累计15个分类，关注成员有19位，主要包括：物流,旅游,餐饮零售,网络游戏,咨询,金融,电子政务,外包,教育,制造,医疗,嵌入式,互联网,交通,电信

    热门标签

    物流 旅游 餐饮零售 网络游戏 咨询 金融 电子政务 外包 教育 制造 医疗 嵌入式 互联网 交通 电信

    最新资料