Flood prone area’s mapping, modeling and zoning by using GIS and RS techniques.
Anam Munawar Assistant Manager GIS The Urban Unit M.Phil. Space Sciences Department of Space Science University of the Punjab.
Basic Essentials of research Work Introduction to study area Methodology/flowchart Input Data Outcomes/Findings Results & conclusions Recommendations Presentation Scheme
Basic Essentials of Research work Theme of Research work: This Research focuses on practical applications of GIS tools for flood hazard mapping and resource management. Emphasized Field: This research visibly illustrates how to use GIS and RS to make flood hazard assessment and management easier to do and increase productivity while addressing water, floodwater and storm water systems.
When the amount of water level rises up to a certain level, after which the capacity of that particular water body ends, it results in overflow of water in the surrounding land. This phenomenon is termed as “flooding” . Flash Floods: Floods that can occur in a very short period of time due to heavy amount of rainfall associated with a thunderstorm. Flash floods lasts for may be a few minutes or some hours. It is difficult to be monitored and processed because of its shorter duration and localized nature. Coastal floods: Floods that can me be resulted due to flash flooding or tidal surges. Riverine Floods: Floods that occur when amount of water rises due to heavy rainfall or melting of ice. Dam Failure floods: The worst form of flood occurs, when a dam fails working, as the strong speedily moving downward water destroys everything that comes across. Introduction to Flooding..
FLOOD MANAGEMENT TECHNIQUES Non- STRUCTURAL METHODS need more budget and physical developments to take place for protection measures before/during or after the exposure of floods. NONSTRUCTURAL METHODS involves preprocessor alarms, future forecasts and planning before flood comes for fewer damages to occur. That’s why; non structural techniques are being more preferred in recent many decades as these are cheap and effective.
Study AREA District Muzaffargarh, Pakistan. stripped between River Indus and River Chenab In case of any disturbance in the water level of these rivers or their tributaries, there will be a direct impact on the study area. Major area of the district is composed of barren land and sand dunes.
Technical Requirements … Below is the list of soft wares, which were used during different phases of this research work: ArcMap 9.3 ERDAS IMAGINE 9.2 HEC_RAS 4.0 Google earth pro 4.2
Input Datasets/Sources… For flood mapping, all flood data layers was provided by THE URBAN UNIT. The last 20 years Rain fall data and other metrological data was retrieved from Pakistan Metrological department, Lahore. Hydrological data was obtained from Punjab irrigation department. DEM with 15m resolution and Satellite image of Landsat ETM Plus with 30m resolution were downloaded from the website www.glcf.com.
Flood zones are the land areas that are defined as less or more hazardous on the basis of future risk levels. Flood zonation is found to be fundamental line of attack for suitable development and for investigation of the ecological and environmental consequences. Research workflow chart
Raster processing based mapping This RS based land use Map is showing that vegetation has the maximum area covered in District Muzaffargarh. Water and Urban infrastructures are also capturing large significant area.
Vector Data based mapping Irrigation Network
Flood Affected Areas(2014)
Floodplain models are mainly of two types: Hydrologic models Hydraulic Models Hydrologic model identifies the peak flood flows. HYDRAULIC MODELS routes the runoff to determine the surface water profile via stream channels at particular locations along the stream network. GIS based hydraulic models can apply/use different data layers containing different land parameters like land use and drainage network etc. but the basic component of all hydraulic models is DEM with the help of which we can determine stream channel network, water level depth, slope, aspect and many other characteristics of water channels.
All hydraulic model development is completed in following three steps. Pre-processing of data Model execution Post-processing of model Collection of necessary data for the floodplain analysis can be organized as: a) Topographic data b) Obstructions data c) Hydrologic data Topographic data involves Cross Sections Data for the given Rivers and streams and reach length etc. Obstruction data involves bridges and culverts of cross sections. However, the hydrologic data involves the discharge rates for the storm of interest.
Data for Flood Plain Modeling Data has been collected from the following departments: Pakistan Meteorological Department Irrigation and Power Department WAPDA Internet Resources For HEC RAS modeling following data was collected. River cross sections Recorded peak flood data (Long Term) Peak flood data 2010 DEM of the area
DEM for the Study area Major DEM applications include (USGS, 2000): • Delineating watershed boundaries and streams • Developing parameters for hydrologic models • Modeling terrain gravity data for use in locating energy resources • Determining the volume of proposed reservoirs • Calculating the amount of material removed during strip mining • Determining landslide probability Watershed Delineation After DEM has been preprocessed to be used for the watershed delineation, by using Hydrology tools in Arc map, flow direction and flow accumulation were investigated to delineate watershed.
Flow Length Flow length is the distance travelled from a given cell to the outlet along with the surface flow network. It is helpful for identifying areas that are closer to headwater or near the stream outlets. Flow Length Watershed basin
Digital Elevation Model is the main part for flood model building in Hec-Ras as all the watershed information and other important hydraulic parameters are derived from DEM. All hydraulic model development is completed in following three steps. 1.Pre-processing of data 2.Model execution 3.Post-processing of model HEC_GeoRaS is an extension of the arc map that was used for pre-processing of the GIS data Using different functions and applications of HEC_GeoRAS, the GIS data can be obtained in a format which is required for input to the HEC RAS. HEC-GeoRas toolbar contains the following menus:
Ras Geometry Ras Geometry menu contains functions for pre processing of the GIS data and makes layers in a format that can be imported in Hec-Ras directly. RAS Mapping Flood inundation mapping is done by using functions of RAS Mapping that is used for post processing of the HECRAS processed output data. It also contains the functionality for data visualization ApUtiliteis ApUtilities contains data management tools. Help The Help menu is self explanatory. It provides help for any kid of issues relevant to data handling and management in HEC_GeoRAS.
UPSTREAM AND DOWNSTREAM DISCHARGE AT TARBELA DAM (2011) The figure is showing the water discharge flow at Tarbela dam for the year of 2011. Results have shown that downstream discharge flow values are two times greater than that of the upstream discharge flow values.
Maximum Discharge peaks at Chashma, Tounsa and Marala barrages for the last 20 years. [SOURCE: PAKISTAN METROLOGICAL OFFICE, LAHORE.]
RIVER X SECTIONS The data for river cross sections were taken from Irrigation and Power Department. River sections are drawn and shown in the figures shown below. Indus River Cross Section RD 137,000 Indus River
Indus River Cross Section RD 147,000 with Cross Section RD 160,000
Catchment Delineation With the help of DEM data catchment delineation was carried out and shown in the following Figures: Flood Frequency Analysis (Source: Wenner 2010)
HEC GEORAS MODELING RESULTS 100 90 400 80 390 70 • Schematic diagram 380 60.17 I Tounsa-Muzgrh n developed for HEC- d 370 us 50.18 C RAS modeling. R i ver SherShah-Punjnad 360.19 hen 350.20 ab 340.21 40.19 R i ve r 330.22 • extent of flooded 30.20 area is shown in the 320.23 20.21 10.1 next following 310.24 Figures: 300.25 280.27 9.5 260.29 250.30 240.31 220.33 Junction 9.1 Low er Reach 210.34 50.1 40.2
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