Ministry of Water Resources, Government of Bangladesh. Technical Note: 17. STREAM Development of Flood Module

Transcription

1 Ministry of Water Resources, Government of Bangladesh Environment and GIS Support Project for Water Sector Planning EGIS-II Technical Note: 17 STREAM Development of Flood Module (Compiled for Bangladesh from SPIHRAL report) Dhaka November 2000 Environment and GIS Support Project for Water Sector Planning (EGIS II) House # 49, Road # 27, Banani, Dhaka 1213, Bangladesh Phone (880-2) , Fax: (880-2) egis@cegisbd.com Resource Analysis (RA) Zuiderstraat SJ Delft, the Netherlands Tel Fax RA@resource.nl

2 Published by: Environment and GIS Support Project for Water Sector Planning (EGIS II) House # 49, Road # 27, Banani, Dhaka 1213, Bangladesh Phone (880-2) , Fax: (880-2) egis@cegisbd.com And Resource Analysis (RA) Zuiderstraat SJ Delft the Netherlands Tel Fax RA@resource.nl EGIS Technical Note 17 This Technical Note is adapted from part A (flood module) of the report Spihral, Spatial Integration of Hydrological Monitoring and Remote Sensing Application RA/00-399, May It is meant for distribution in Bangladesh only. Date of publication: November 2000 The other reports in EGIS Technical note series 1. Technical note-1: Bangladesh Transverse Mercator Projection, May Technical note-2: North Central Region Digital Elevation Data, August Technical note-3: Area Elevation Curves for BWDB Southwest Regional Projects, February Technical note-4: GIS Atlas for Tangail Area Study, November Technical note-5: GIS Installation Summary, October Technical note-6: Tangail Area Digital Elevation Model, August Technical note-7: Bangladesh National Digital Elevation Model, August Technical note-8: National Database for Bangladesh, August Technical note-9: A Semi-Detailed River Database for Bangladesh, March Technical note-10: Datum and Map Projections for GIS & DPS Applications in Bangladesh, May Technical note-11: River Resources Database, September Technical note-12: A Semi-Detailed Water Body Database for Bangladesh, February Technical note-13: Mosaic of TM images of Bangladesh, April Technical note-14: Mapping the 1998 floods, June Technical note-15: Blue Accounting, February Technical note-16: DGPS System Calibration Report, October 2000

3 Acknowledgement The results as described in this report emerged from the work carried out in the Spihral project. The ESA-DUP programme of the European Space Agency (ESA) provided funding for this project. ESA is kindly acknowledged for all support and making this project possible. Special thanks go to J. Lichtenegger for his support throughout the project and enthusiasm during the meetings in Rome and Delft. The project was jointly designed and coordinated by Jeroen Aerts of Resource Analysis and Ahmadul Hassan of EGIS. The following professionals were of assistance in providing field monitoring data: Timothy C. Martin, Jorunn Fleumer, Khaled Hasan, Shawkat Ali, Aneeqa Shireen, Quazi Khalid Hassan and Omar Faruk. Omar Faruk was responsible for processing field monitoring data; the remotely sensed data was processed and analyzed by Quazi Khalid Hassan; Jorunn Fleumer developed the Digital Terrain Model (DTM) of the study area; Ahmadul Hassan, Shawkat Ali and Timothy C. Martin developed the flood depth and duration computational methodology. Ahmadul Hassan and Jeroen Aerts jointly developed and calibrated the hydrological model (STREAM). This report was written by Jeroen Aerts, Joris de Vente of Resource Analysis and Ahmadul Hassan, Timothy C. Martin, Waji Ullah and Quazi Khalid Hassan of EGIS. The report was reviewed by Lineke Mourits of Resource Analysis and Rob Koudstaal of EGIS. Thanks go to Asifa Rahman for editing and formatting the report.

4 Table of contents Acknowledgement...iii Table of contents... iv List of figures... v List of tables... vi Acronyms...vii Chapter 1 Introduction STREAM Overview SPIHRAL & the ESA-DUP Program Floods in Bangladesh Scope and objective (flood monitoring) Structure of the report... 5 Chapter 2 Study area description The CPP and North Central Area Climate Geomorphology and hydrology Land use and agriculture Water levels Chapter 3 Data description ERS-SAR acquisition imagery Near Real Time(NRT) image data collection Acquired images ERS-2 SAR image pre-processing, georeferencing and co-registration Additional remote sensing & GIS data Radarsat data Digital Terrain Model (DTM) Groundtruth data Chapter 4 Methodology Introduction SAR data for flood monitoring Classification of flood extent with SAR images Introduction Classification of ERS -2 SAR images of Classification of RARDARSAT SAR images of Flood extent classification enhancement Chapter 5 Comparison of flood depth mapping using SAR data Introduction Land water interface method Area elevation method Incremental elevation method Discussion and comparison of results for all three methods Chapter 6 Verification and application of FDD computations Introduction Classification and mapping FFD using the area elevation method Water classification Flood depth duration computation... 49

5 6.3 Verification of results of FDD computations using the STREAM hydrological model STREAM North Central (NC) model FDD: Volume simulation Conclusions Applications of FDD estimates Flood damage assessment Drainage capacity Fisheries resources Crop suitability Chapter 7 Conclusions and recommendations Appendix A: Water Levels in the Study Area in 1998 Appendix B: Field Monitoring Form Appendix C: Photographs and measurement results of monitoring sites List of figures Figure 1.1: STREAM river basin management structure... 2 Figure 1.2: STREAM: Water balance algorithm... 2 Figure 1.3: The Ganges, Brahmaputra, Meghna basin... 3 Figure 2.1: Geographical position of the north central- and the CPP area in Bangladesh... 8 Figure 2.2: Major rivers and some of the larger tributaries in Bangladesh Figure 2.3: Average flooding condition in the north central region Figure 3.1: Two ERS SAR descending images, acquired by the RAPIDS ground station at 2 nd June (left) and 31 st August (right) respectively Figure 3.3: Field data collection sites Figure 3.4: An example of the physical behavior (left) and spectral pattern (right) of b. aman Figure 4.1: Overview of the methodological approach Figure 4.2: A: Mean signatures of land cover types for the ascending images from track-484 B: Mean signatures of land cover types for the descending images from track Figure 4.3: Flowchart of the applied classification methodology Figure 4.4: Relative Elevation, Flood cells and Digital Terrain Model as used for the classification and classification enhancement of the North Central Area Figure 5.1: Calculated and measured water levels for floodcell Figure 5.2: Histogram of boundary pixels and corresponding heights on three image dates Figure 5.3: Cumulative elevation for floodcell Figure 5.5: An example of an area elevation curve (Tangail, CPP flood cell No.1) Figure 5.6: Calculated and measured water levels for flood cell 49 (Area elevation method) Figure 5.7: Calculated and measured water levels for floodcell 49 (Incremental method) Figure 5.8: Histograms of flooded and non flooded pixels for six dates. In these graphs the development of the flood from pre monsoon to monsoon and post monsoon can be seen.. 41 Figure 5.9: Histogram of flooded and non-flooded pixels on 8 th of August in floodcell Figure 5.10: Histogram of flooded and non flooded pixels on 25 th of September in flood cell Figure 5.11: Comparison of calculated and measured water levels for all three methods for the 13 reference floodcells Figure 5.12: Comparison of calculated and measured water levels for all three methods in floodcell

6 Figure 5.13: Flood depth maps as calculated with the three different methods and flood extent maps as classified from RADARSAT images Figure 6.1: Flood 1999, extent maps of Tangail study area using ERS-SAR data Figure 6.2: Flood 1999, extent maps of the Jamalpur study area using ERS-SAR data Figure 6.3: Flood depth in the Jamalpur study area as calculated with the area elevation method Figure 6.4: Flood depth maps for the Tangail study area Figure 6.5: Flood depth maps for the whole North central region as was determined with Radarsat images Figure 6.6: Demonstration of flood duration type and percentage for F1 land cover part of the Tangail study area Figure 6.7: Simulated hydrograph plotted against the measured hydrograph for a downstream gauging station Figure 6.8: Rain, evapotranspiration FDD volume and STREAM calculated water volumes in the North Central region Figure 6.9: Indication of flood damages to infrastructure in part of the North Central region Figure 6.10: Drainage map of the North Central area Figure 6.11: Filling rate in the flood cells in part of the Tangail study area Figure 6.13: Habitat preference index for different guilds in the Tangail study area Figure 6.14: T.Aman suitability map based on flood depth characteristics Figure 6.15: Deep water Aman suitability map based on flood depth Figure 6.16: Combined presentation of Aman suitability based on flood characteristics and soil types List of tables Table 1.1: Important flood characteristics for flood prediction and assessments of damage likely to be produced (adapted from: Martin et al. 1998) Table 2.1: Summarised average climate data for the CPP area (source: FAP3 1993)... 9 Table 2.2: Land cover types and an indication of dominant crop types Table 3.1: Satellite data used for ERS data pre- processing Table 3.2: Acquired ERS-SAR-2 images by the RAPIDS ground receiving station in Dhaka (Bangladesh) during the monsoon season of Table 3.3: Polygon List of the Jamalpur area Table 3.4: Polygon List of the Tangail area Table 4.1: Objectives and data used for specific activities within the study areas Table 4.3: Class names for the classification scheme of ERS-2 SAR images of Table 4.4: Classification of classes based on radar backscatter value (db) for RADARSAT SN images. 28 Table 4.5 Relative land classes based on normalised DEM Table 4.6: Decision matrix for distinction in flooded (F) and non- flooded areas (NF). A total rank of 6 was regarded flooded, the others non-flooded Table 5.1: Comparison of gauge readings to compute water levels for three methods in 13 sample flood cells Table 5.2: Comparison of flood depth and percentage of flooded area (EGIS 2000) Table 6.1: Accuracy assessment for the single date classification of flood extent Table 6.2: Comparison of actual and computed flood depth (all measurements are in cm) Table 6.3: Comparison between computed and measured depth using RADARSAT SAR data Table 6.4: Percentage of the study area utilized for fish habitats

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