using ArcGIS Agus Wibowo MSc in IT for NRM Bogor Agricultural University

Transkripsi

1 Watershed Application using ArcGIS Agus Wibowo MSc in IT for NRM Bogor Agricultural University Aplikasi GIS untuk Watershed Menentukan batas DAS / watershed boundaries Menentukan distribusi curah hujan di DAS o Polygon Thiessen o Isohyet 1

2 Data Used Data Digital Elevation NASA Shuttle Radar Topography Mission (SRTM) Dapat di-download di Tersedia Data SRTM 90m Version 4 Website Data SRTM 2

3 Search Data SRTM 3. Click untuk mencari data 1. Pilih format data 2. Click lokasi data Download Data Click untuk download Data hasil download 3

4 Software: ArcGIS Desktop + Spatial Analyst Tools Watershed Delineation Creating a depressionless DEM Flow direction Flow Accumulation Stream network/line Stream link Stream order Delineating watersheds Sumber: ArcGIS Desktop Help 4

5 Add Data to ArcMap - 1 Ekstrak Zip file data hasil download Start ArcMap Aktifkan ArcToolbox Click menuconversion tools ASCII to raster Add Data to ArcMap - 2 Input:..\srtm_58_14\srtm_58_14.ASC Output:..\SRTM_v4\jabar_dem Output data type: INTEGER Click OK 5

6 Add Data to ArcMap - 3 Ubah Symbology Peta Double Click Layer Pilih jenis Color Ramp Click untuk membalik urutan warna 6

7 Cropping Data DEM Gunakan ArcToolBox Spatial Analyst Tools Extraction Untuk ekstraksi berdasar luasan misal poligon batas admin Jawa Barat gunakan Extract by Mask. Buat raster poligon batas admin Jabar terlebih dahulu. Buat Mask Batas Admin Jabar Pilih poligon Jabar o Load batas admin Indo_prop.shp o Select Jawa Barat Konversi Poligon ke raster o Gunakan Arctoolbox o Conversion tools To Raster Polygon to Raster Atur ukuran sel (10 m) 7

8 Extract by Mask / Cropping Gunakan menu Arctoolbox Spatial Analyst Tools Extraction Extract by Mask Hasil Extract by Mask Spatial Analyst Overview of Hydrology Tools Basin: Creates a raster delineating all drainage basins within the Analysis window. Fill: Fills sinks in a surface raster to remove small imperfections in the data. Flow Accumulation: Creates a raster of accumulated flow to each cell by accumulating the weight for all cells that flow into each downslope cell. Flow Direction: Creates a grid of flow direction from each cell to its steepest downslope neighbor. Flow Length: Calculates upstream or downstream distance along a flow path for each cell. Sink: Creates a grid identifying all sinks or areas of internal drainage. Snap Pour Point: Snaps selected pour points to the cell of highest flow accumulation within a specified neighborhood. SnapPour: Snaps selected pour points to the cell of highest flow accumulation within a specified neighborhood. Stream Link: Assigns unique values to sections of a raster linear network between intersections. Stream Order: Assigns a numeric order to segments of a grid representing branches of a linear network. Stream To Feature: Converts a raster representing a raster linear network to a feature class. StreamShape: Converts a grid representing a raster linear network to a shapefile. Watershed: Determines the contributing area above a set of cells in a grid. 8

9 Watershed Delineation Creating a depressionless DEM Flow direction Flow Accumulation Stream network/line (Map Algebra) Stream link Stream order Delineating watersheds Sumber: ArcGIS Desktop Help Creating a depressionless DEM - 1 Sink dan Peak terjadi resolusi data atau pembuatan nilai integer Sink dan peak harus dihilangkan, jika tidak maka delineasi jarinagn drainase tidak kontinyu. 9

10 Creating a depressionless DEM - 2 Arctoolbox Spatial Analyst Tools Hydrology Fill DEM hasil Waktu: 4 menit (Core 2 duo 2.33 GHz, RAM 4GB) Create Flow Direction Menentukan arah aliran air Evaluasi 3 x 3 cell, berhenti pada tengah cell dan evaluasi dengan nilai cell tetangganya. Jika arah aliran ke utara maka nilai cell tengah diganti dengan cell tsb. Nilai cell antara Contoh untuk illustrasi 10

11 Compute Flow Direction ArctoolBox Spatial Analyst Tools Flow Direction Waktu: 30 detik Hasil Flow Direction Compute Flow Accumulation Untuk menentukan jaringan sungai Waktu: 1' 6 Hasil Flow Accumulation 11

12 Extract Stream Network - 1 Ubah symbology peta FlowAccumulation menjadi classified dengan 5 klas secara Natural Breaks. Maka akan terlihat angka treshold jaringan sungai. Extract Stream Network - 2 ArctoolBox Spatial Analyst Tools Map Algebra Single Output Map ALgebra 12

13 Stream Link Stream Order Metode: 13

14 Watershed Delineation Watershed Outlet / Pour Points Create shapefiles (point) using ArcCatalog Add pour point pada pertemua cabang sungai. Pour Point Buat pour point sesuai kebutuhan 14

15 Watershed Delineation Hasil kurang bagus, perlu pour point yang banyak. Automatic Basin Delineation Secara otomatis delineasi basin / watershed area untuk seluruh data. ArctoolBox Spatial Analyst Tools Hydrologi Basin 15

16 Compute Flow Length Flow length is the distance travelled from any cell along the surface flow network to an outlet. This can be used to find areas that are closer to headwater locations or closer to stream outlets. ArcToolBox Spatial Analyst Tools Hydrology Flow Length Hasil Flow Length 16

17 Hillshade Untuk memberi efek tampilan 3D Arctoolbox Spatial Analyst Tools Surface Hillshade Overlay dengan Flowlenght dengan transparancy 35% Referensi ArcGIS Desktop Help Hydrologic Modeling and Watershed Delineationhttp://courses.washington.edu/esrm590/lessons/hydrology/index. html SRTM 90m Digital Elevation Data Data Batas Administrasi, jaringan jalan, lokasi kota, 17