Consideration on the Use Sentinel1 Radar Image and GIS for Flood Mapping in the Lai Giang River Basin of Binh Dinh Province (Central Coast Vietnam)45238

Consideration on the Use Sentinel-1 Radar Image and GIS for Flood Mapping in the Lai Giang River Basin of Binh Dinh Province (Central Coast Vietnam) Ngo Anh Tu(1) (*), Grivel Stéphane(2), Nguyen Huu Xuan(1), Phan Van Tho(1) (1) Quy Nhon University, Binh Dinh, Vietnam (2) Ministère de la Transition écologique et solidaire-Paris, France * Correspondence: ngoanhtu@qnu.edu.vn Abstract: The research of building a flood mapping in Lai Giang basin of Binh Dinh province in 2016 on the use Sentinel-1 radar image and GIS, initially determines the construction of flooded square in the studied area based on the results of the process of scattering water value threshold, extracting flooded areas on the radar image This flood mapping is combined with the depth measured from the flood in 2016 traces to apply GIS techniques to create of flood depth map The results of the study provide a new way of quickly creating flood maps from radar satellite images Keywords: Flood mapping; Sentinel-1 radar image; GIS; Lai Giang river basin; Central Coast Vietnam Introduction Recently, global climate change and flood disasters have caused major impacts that directly affect the include loss of human life, damage to property, destruction of crops, loss of livestock (Gautam et al 2019) In fact, the situation of floods has become more and more complicated, making management and forecasting difficult, causing serious losses to the development in Vietnam This has set the hydro-meteorological forecasting agencies the need for practical and timely solutions in order to make rapid and timely flooding forecasts From there, contribute to minimize the damage caused by floods The Lai Giang river basin of Binh Dinh province in the South Central Coast has a tropical monsoon climate This basin is proven that this area is more prone to natural disasters than any other region in the country First, due to the local unfavourable geographical, topographical, and meteorological conditions along with the global climate change (Vo et al 2019) The region experiences an increase in annual rainfall about 1.750 2.400 mm (BDPC 2018) However, the rainfall is not evenly distributed over time, concentrated from September to December In addition, The Lai Giang river basin is frequently affected by typhoons and tropical low hamlets On average each year, this basin has experienced an average of to floods and it has caused many losses of lives and people's wealth According to the statistics of the Provincial Steering Committee for Disaster Prevention and Search and Rescue, during the historic flood from 14 to 18 November 2013, there were severe losses: 19 deaths and 14 deaths More than 101,900 houses were flooded with 510,000 people affected, of which 292 houses collapsed, 418 houses were seriously damaged, transport and irrigation infrastructure was destroyed 2,125 billion dong The December 2016 flood has caused the most severe floods in recent years, it has caused many damages to the people and the transport, irrigation and educational infrastructure, and etc In the three districts and the battlefield, it was flooded from 0.5 to 1.5 meters, some places were over 1.5 meters (BDPC 2018) Due to the serious nature of floods in the river basins of Binh Dinh province in general and the Lai Giang river basin in particular There have been many typical studies on the application of hydrological and hydraulic models to build flood maps such as: Trinh Viet An et al 2009 studied “Current situation of flood drainage in Lai Giang estuary”; in 2013, Nguyen Van Hieu et al with the application MIKE FLOOD software to calculate flood and simulation plans building dykes in Lai Giang river basin; Tran Huu Tuyen has established the program for risk of attachment of river flow in Lai Giang river basin of Binh Dinh province in 2017; Bui (2018) built a flood map of Lai Giang river basin of Binh Dinh province These researches have the common feature of using hydrological and hydraulic models to identify flooded areas However, the limitation of this method is the input data depends on the topographic map, lack of rain gauges, flow measurement, water level, However, in reality the characteristics of the river basin are always fluctuating in surface cover, amount of sediment, morphology of the river bed, (Ali et al 2019) Therefore, the use of topographic sections, roughness coefficients for hydrological and hydraulic models will have many errors In particular, the creation of fast flood maps is a disadvantage of flooding models These limitations, the remote sensing technology has gradually overcome in rapid monitoring of flooded areas (Perrou et al 2018) In recent times, the satellites image have been increasingly improving the mapping methods from space also under difficult circumstances, such as thick clouds, rugged terrain or other inflexible geographical or meteorological conditions, capable to acquiring imagery both day and night (Tavus et al 2018; Gautam et al 2019) Inside, the Sentinel-1 is a SAR mission of the Copernicus Program of European Space Agency (ESA) This satellite has been used extensively in mapping flood inundation and has brought about practical benefits for disaster monitoring (Holtgrave et al 2018; Bipinchandra et al 2019; Borah et al 2019; Gautam et al 2019; Kumar 2019) Methodology 2.1 Datasets Through research and survey of the study area, shows that in 2016 is called the historic flood of the basin The sentinel-1 SAR data in C-band sensor have been used in this study At the same time, researches to collect DEM (digital elevation model)-12.5m data of Lai Giang river basin, administrative map, flood mark were also collected to extract the necessary information for the study Table Dataset to build flood map No Data Type / Resolution Year Sources S1A-IW-GRDH VV+VH/10 2016 Copernicus Open Access Hub S1A-IW-GRDH VV+VH/10 2018 Copernicus Open Access Hub ALOS PALSAR Raster/12.5 2011 Alaska Satellite Facility GPS GPX 2018 Field survey Flood trace GPX 2016 Investigate flood marks 2.1 Flowchart and methodology The paper proposes a research process to develop flood maps from satellite images as follows in figure Figure Logical flowchart of study The Satellite image data is downloaded from the website for free https://scihub.copernicus.eu/ In this case, the Sentinel-1 satellite constellation consists of Sentinel-1A and Sentinel-1B were used Sentinel-1 data is then processed on specialized software combining DEM data to image the georeferencing in the study area The paper uses algorithms to extract data on the water layer to produce flooded and non-flooded areas Finally, this data is combined with the depth of flooding to provide a flood depth map of the study area Remote sensing image processing: The study has used the satellite image of Sentinel1 dual polarization VV and VH with 10m spatial resolution in December 16th, 2016 The satellite data used in the present study are showed in the Figure Pre-flood imagery acquired on December 16th, 2016 and post-flood imagery acquired on December 5th, 2018 were used to identify changes in inundation over study area Figure Sentinel-1 SAR data acquired in November 04, 2016 The data is processed in SNAP toolbox (open source), which can be downloaded from the Copernicus Services Access Hub (https://scihub.copernicus.eu/) To analyse flood mapping, all Sentinel-1 images are first preprocessed with orbit correction, thermal noise removal, calibration to sigma naught, Range Doppler terrain correction and de-speckling (Lee 7x7 speckle filter) by the SNAP toolbox (Jüssi 2016) Details of processing results are shown in the following figure Figure a) Original image; b) After calibration: c) After filtering Lee Field survey method: The study conducted random allocation of surveys for the entire basin For each commune, 30 points were surveyed through GPS measuring equipment to collect flood trace information (Figure 5) Figure Survey points on flood marks There were 200 sites surveyed in 2018, and then the survey data is processed on GIS, exported to the map as shown in Figure Figure Survey points in the Lai Giang river basin GIS application method: This method is used after extracting the flooded area from satellite imagery Later, the GIS technique uses algorithmic stacking to determine the depth of flooding from the results of surveying flooded areas identified by satellite images In this study, QGIS software was used by us to build a flood depth map Results 3.1 Study area and the flood event The Lai Giang River is a basin of 1272km2 (Binh Dinh Province-Central Vietnam) This fluvial system is two tributaries (An Lao: 75km; Kim Son: 64km) This basin has relatively complex topography Characteristic for the coastal terrain of the South Central Coast region, this area has short topography, the West borders on the high mountains, the East is a narrow coastal plain Therefore, with this type of terrain has affected the river, high slope, flood concentration time is very fast Figure Study area map The flood event occurred in Lai Giang basin on December 16th, 2016 has caused damages in infrastructure, houses and offices, and also caused the injury of persons (Figure 7) Figure Examples to damages after December 16th, 2016 flood in Lai Giang basin (photo: AnhTu) 3.2 The Mapping Procedure After the completion of SAR pre-processing steps, the study used hydrological maps of the Lai Giang river to extract the flooded area from satellite imagery through GIS technology the produced images have been pre-processed prior to the final flood-map generation (Figure 8) Figure Results of change detection using thresholding Flood status map from satellite image integrated in GIS to combine the results of flood depth measurement points in 2016 from GPS And then, using the Kriging interpolation algorithm to calculate the interpolation of the space to determine the depth of flooding Parts of the results are shown in Figure Figure Flood map in December 16th, 2016 in Lai Giang basin Through flood data (Figure 9), the study has identified flooding areas in the Lai Giang river basin (Table 2) In Table 2, the largest flooded area is in the downstream area of the Lai Giang river basin The flooded area is from 1.5-2.0 m mainly in Hoai An and Hoai Nhon districts Table Statistics of flood depth in Lai Giang river basin Depth (m) An Lao district % Hoai An district % Hoai Nhon district % - 0.5 55.44 43.39 1977.46 30.27 2746.50 30.16 0.5 - 1.0 40.34 31.57 2142.89 32.80 2660.26 29.21 1.0 - 1.5 25.24 19.75 1680.07 25.72 2739.74 30.08 1.5 - 2.0 6.76 5.29 732.78 11.22 961.30 10.55 Total 127.78 100.00 6533.20 100.00 9107.80 100.0 Conclusions and discussion The Sentinel - radar sensing satellite image system has the advantage of providing data and helps to view the flooded area compared to optical satellite imagery, because floods occur mainly on cloudy days Through research results, it shows the important role of satellite image data in the management of natural resources and environment today Especially the monitoring and evaluation of natural disasters, with the advantage of being observed in a cloudy weather environment during storms and floods In addition, the fieldwork combined with the construction and zoning of flood depth plays an important role This helps managers and citizens to have a visual look At the same time, it is an effective tool to help prevent and minimize risks of human and property damage during the rainy season Acknowledgment The authors would like to thank Quy Nhon University, which is the host agency for ministerial-level research projects “Researching on application of rainfall data from radar satellite images and mathematical models in rapid forecasting of flood risks Case study of Lai Giang river basin, Binh Dinh province, Central Coast Vietnam” They provided data for us to successfully implement this paper References Ali P.Y, Jie D., Xuan S., Ram, A (2019) Improved Bathymetric Mapping of Coastal and Lake Environments Using Sentinel-2 and Landsat-8 Images Multidisciplinary Digital Publishing Institute, Published online 2019 Jun 21, 19(12):27888 BDPPC (Binh Dinh provincial People's Committee) Promulgating flood coping plans in 2018 in Binh Dinh province, No 3704 / QD-UBND 30 pages Bipinchandra M., Romeji N., Loukrakpam C (2019) Flood Hazard Risk Assessment and Mapping of a Sub-watershed of Imphal River Basin, Manipur, India Applications of Geomatics in Civil Engineering LNCE, Vol 33, pp 155-163 Borah, S.B., Sivasankar, T., Ramya, M.N.S et al (2018) Flood inundation mapping and monitoring in Kaziranga National Park, Assam using Sentinel-1 SAR data Environ Monit Assess 2018 Aug 15;190(9):520 doi: 10.1007/s10661-018-6893-y Bui Anh Kiet (2018) Built a flood map of Lai Giang river basin of Binh Dinh province Master thesis, Da Nang University of Technology Gautam D., Hiroyuki M., Mukand B (2019) Applications of Sentinel-1 synthetic aperture radar imagery for floods damage assessment: a case study of Nakhon Si Thammarat, Thailand The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-2/W13, 2019 ISPRS Geospatial Week 2019, 10-14 June 2019, Enschede, The Netherlands Holtgrave, AK., Förster, M., Greifeneder, F., Notarnicola, C., Kleinschmit, B (2018) Estimation of Soil Moisture in Vegetation-Covered Floodplains with Sentinel-1 SAR Data Using Support Vector Regression Journal of Photogrammetry, Remote Sensing and Geoinformation Science April 2018, Vol 86, Issue 2, pp 85-101 Jakovljević, G., Govedarica, M (2019) Water Body Extraction and Flood Risk Assessment Using Lidar and Open Data Climate Change Adaptation in Eastern Europe pp 93-111 Jüssi, M (2016) Synthetic Aperture Radar based flood mapping in the Alam-Pedja Nature Reserve in years 2005-2011, University of Tartu, Faculty of Science and Technology, Institute of Ecology and Earth Sciences, Department of Geography, 1-41, (2015) Kumar R (2019) Flood Inundation and Hazard Mapping of 2017 Floods in the Rapti River Basin Using Sentinel-1A Synthetic Aperture Radar Images Applications and Challenges of Geospatial Technology pp: 77-98 Perrou, T., Garioud, A., Parcharidis, I (2018) Use of Sentinel-1 imagery for flood management in a reservoir-regulated river basin Earth Science 12(3), 506-520 Tavus, B., Kocaman, S., Gokceoglu, C., Nefeslioglu, H.A (2018) Considerations on the use of Sentinel-1 data in flood mapping in urban areas: Ankara (Turkey) Remote Sensing and Spatial Information Sciences Vol XLII-5, pp 575-581 Tran, H.T (2017) Established the program for risk of attachment of river flow in Lai Giang river basin of Binh Dinh province Hue University journal of Science, Vol 126, No 7A (2017) Trinh, V.A., Nguyen T.T.H., Dang H.T (2009) Current situation of flood drainage in Lai Giang estuary Science and Technology of Water Resources Institute of Vietnam Available online: http://www.vawr.org.vn/index.aspx?aac=CLICK&aid=ARTICLE_DETAIL&ari=1695&lang =1&menu=khoa-hoc-cong-nghe&mid=995&parentmid=982&pid=2&storeid=0&title=hientrang-thoat-lu-vung-cua-song-lai-giang (accessed on 10 September 2019) Vo N.D., Vo T.D., Nguyen C.C (20s19) Landsat Image Processing Application for Binhdinh Shoreline Change International Conference on Asian and Pacific Coasts APAC 2019: APAC 2019 pp 325-329  ... simulation plans building dykes in Lai Giang river basin; Tran Huu Tuyen has established the program for risk of attachment of river flow in Lai Giang river basin of Binh Dinh province in 2017;... application of rainfall data from radar satellite images and mathematical models in rapid forecasting of flood risks Case study of Lai Giang river basin, Binh Dinh province, Central Coast Vietnam” They... areas in the Lai Giang river basin (Table 2) In Table 2, the largest flooded area is in the downstream area of the Lai Giang river basin The flooded area is from 1.5-2.0 m mainly in Hoai An and