1 / 20

By Mr. Sombat Chuenchooklin

Application of geographic information systems for flood extent determination in floodplain : a case study in the Yom River Basin in Phichit Province. By Mr. Sombat Chuenchooklin. Working group: CGIST at Lower-Northern Regional Office, Phitsanulok E-mail: sombatc@nu.ac.th.

gaynell
Download Presentation

By Mr. Sombat Chuenchooklin

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Application of geographic information systems for flood extent determination in floodplain : a case study in the Yom River Basin in Phichit Province By Mr. Sombat Chuenchooklin Working group: CGIST at Lower-Northern Regional Office, Phitsanulok E-mail: sombatc@nu.ac.th Department of Civil Engineering, Faculty of Engineering, Naresuan University, Phitsanulok 65000 Thailand

  2. Introduction • Determination of flood extent in floodplain is difficult due to flat topography and there are many obstructs. • By using hydrologic & hydraulic principles incorporated to physical characteristics, flood can be estimated. • Those basins characteristics can be found as existing database presented by GIS. • Those data included some attributed data which has been digitized from aerial map i.e. roads, streams, water sources, wetlands, contour-lines, land-uses, soil series, rainfall-gauges, and local administration boundary as well as location of villages.

  3. Objectives of the study • To use of some existing data and data generation using GIS techniques to generate some basically parameters in the Hydrological Model based on limit data. • To compute flood volume and inundated extent in the floodplain area in ungauged basin for a given period using appropriate techniques in hydrologic & hydraulic models.

  4. Materials & Methods Steps to estimate flood extensive in river floodplain • GIS, topographic map & basically data • Basin characteristics, streams, slope • Soil & vegetative cover, land-use • Cross-sectional profile of floodplain & main streams • Rainfall data from rain gauges in basin • Meteorological data, max-min temperature, etc. Input data • Draw sub-basin characteristics & contours • Generate rainfall isohyets, ET using ArcView GIS • Compute surface runoff, traveling time from each sub-basin to floodplain using appropriate hydrology techniques i.e. synthetic unit hydrograph using Gamma function • Calculate over-bank flow from river to floodplain using river hydraulic analysis model (HEC, 2001) • Estimate inundated volume & extent boundary Process Output Flood volume & extensive map

  5. Hydrological studying

  6. Study area & Chaophya R. Basin Kaengsuaten dam site Ping Enlarger of the Yom Basin Wang Maeyom weir Maesong PRAE Maethang Yom Nan Pasak Thaphae Existing Project Sakaekrang SUKHOTHAI Chaophya Central Plain Rice’s Bowl Maeklong Thajean Road Stream Bangprakong Irrigable area PHITSANULOK KAMPAENG PHET PHICHIT Study area NAKHONSAWAN

  7. Existing database in the Yom R. & its catchments • Area of 1,705 sq.km. in Kampaengphet & Phichit. • Flat sloping land lay from west to east & north to south ranging from 0.0001 to 0.0005. • There are 7 sub-basins divided with average size of 41.18 sq.km, average stream length of 7.893 km. • Most side-flow runoff comes from the west via Kampaengphet to the Yom R. in in Samngam, Phopratabchang, Buengnarang & Phothale in Phichit. • Floodplain of the Yom with normally 1-3 m. deep by flood in September-October. • Most of vegetative cover over the basin is rice. • Sugarcane is popular growing in upland area.

  8. Contours construction based on flood recorded Flooded photograph interpreted from satellite was used for contour-lines construction (adapted from JICA, 1999) Study area

  9. Hydrological studying 3-D landslope, streams & floodplain of the Yom using GIS

  10. Hydrological studying 7 Sub-basins as runoff studying, using ArcView GIS

  11. Hydrological studying Crop name Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flood 2 1 A. HYV rice in lowland floodplain 1 3 B. HYV-rice in middle zone 2 1 1 Vegetables C. Plants in upland zone1 D. Plants in upland zone2 corn Mungbean E. Plants in upland zone3 sugarcane C B A D E Cropping pattern in Phopratabchang as water utilization in the water budget model HYV-rice HYV-rice Flooded zone

  12. Hydrological studying • Side-flows 1-hr synthesized unit hydrograph using Nash-model & Gamma function • Basin characteristics based on US. Army Crop of Engineers method applied with Nash U.H. whereas tp is time to peak discharge, S is channel slope, L and Lc are stream length measure at the longest point and from the centroid of basin, and Ct, Cp, a1, a2 are coefficients getting from linear regression, (Linsley et al., 1988; Jira, 2003). a), b) Runoff hydrograph synthesized

  13. Hydrological studying Daily rainfall from various rain-gauges in the basin. Daily river flow from RID’s gagging stations at upstream & downstream of the study area in the Yom R. in 2001

  14. Hydrological studying Spatially annual rainfall in study area in 2001 using ArcView GIS

  15. Hydrologic & Hydraulics studying Result of floodplain charac Elevation-Volume-Area Result: local streamflow hydrographs

  16. Hydrologic & Hydraulics studying • Total mean annual rainfall in 2001 = 1,146.3 mm • Rainy days = 99, mean daily rainfall = 11.4 mm • Max. temp.=32.6, min. temp.=23.6, Humidity=75.5%, Sunshine duration=6.9 hr/d, Evap.=4.28 mm/d • Runoff coefficient in rational formula = 0.337 • Total Side-flows volume=742.35 MCM or 14.9% of annual flow at Y17 (Samngam) =4,984 MCM • Return period of max. flood depth in the river measured at Y17 and analysis based on Gumbel distribution: in year 1995 the return period (Tr) =38yr and max. water level at +38.14 m(MSL), while in 2001 the Tr=5 yr +37.57m, and in 2002 with Tr=50yr (+38.24m) • Flooded area of 234.231 sq.km occurred in year 2001.

  17. Hydraulics studying Distribution of flood flow along the Yom R. Simulated result of flood extent on 26 September using HEC-RAS (HEC-2001)

  18. Flood photograph from RADARSAT was used to verify flood extent & flood flow direction on 20 September (GISTDA, 2002)

  19. Hydraulics studying Flood flow pattern of the Yom R. in Phopratabchang

  20. Conclusion & Recommendation • Daily flood storage and inundated area in the study site can be estimated corresponding local inflows, overflow from bankfull of river, existing database from generated contours & basin characteristics using GIS techniques and hydrologic models. • Most of flood came by overtopping from river bank due to sub-catchments are smaller size than overall river basin area. • Flood risk map can be processed corresponding GIS, hydrological statistics, and hydrodynamic model, which can be developed and extend to local administration offices and farmer in order to change or shift cropping pattern in floodplain and avoiding flood. • Infiltration & percolation as losses from surface runoff & flood downward to underground can be considered as flood reduction by temporarily storing into groundwater zone. • Many sandpits in the basin can be used to reduce flood by infiltration processed which needs to further research. Thank! to whom supported useful resources i.e. RID, TMD, ESRI, GISTDA, HEC, and ones in ref. (…..).

More Related