Satellite data and geomorphological land classification map for evaluating flood risk: A study in Greater district zone Marju Ben Sayed1, Shigeko Haruyama2 Graduate school of Bioresources, Mie University, 1577 Kurimamachiyacho, Tsu city, Mie Pref. Japan1, 2 Key words: Land use/land cover change, Sadar , Greater Dhaka, GIS

1 Introduction in Dhaka city but also on the surrounding city area. From the Digital Elevation Model (DEM), changes in built up Flood is a common phenomenon in the capital city Dhaka, area (20%) have occurred in almost all elevation range . Almost every year a large portion of the city (1m-6m). Agricultural land use associated with high becomes flooded due to heavy rainfall and spilling water elevation range converted mostly into built up are and bare from the surrounding rivers. The city lies on the land, and at the same time low elevated agricultural land river; Brahmaputra, downstream part of three major also has been converted to build up zone to meet the Ganges and Meghna. Floods of unusually large demand for housing to accommodate the rapidly growing magnitude and long duration happen in the country population. affecting the majority of the population of Dhaka city and severely disrupting the socio-economic activities. Such The northern part of Dhaka city is located in the terrace devastating floods are 1954, 1 987, 1988, 1998, 2004 and zone. Based on the elevation range and geologic evolution, 2007 and considered to be the worst ones. The purpose of terrace has been divided into three types such as higher, the study is to evaluate flooding risk using satellite data middle and lower. The higher terrace has an elevation and geomorphological land classification map concerning higher than 5.5m, are mostly located at the upper part of with the big flooding events and urbanization of greater the study area and covered with commercial and housing zone. activity purpose. The natural levee lies between 2m and 5m. It also has been divided into 3 types, in the study area 2 Data and Methodology natural levee works as a natural embankment during The data has been collected from, the US Army normal flood but submerged during extraordinary flood Topographic sheet (Scale 1:250,000) of 1955 and like 1988, 1998, 2004 and 2007. Lower natural levee has geomorphological map of the Brahmaputra-Jamuna River an elevation between 2.5 and 4.0 m located in the lower and Ganges River plain (1:1,000,000) by M.Oya (1976) part of the study area are submerged at the normal flooding was used for preparation of our base map, Dhaka district condition. Back swamp divided into 3types, the higher one land elevation map and ASTER data for preparation of has an elevation between 1.5m and 2m, are mostly located Digital Elevation Model (DEM) was downloaded from the at the Manikganj Sadar Upazila zone of the study area USGS website. Field survey data has been collected to around the higher natural levee zone, and which became measure ground control points with the ground covered with settlements and commercial activity purpose verification data by the Geological Survey of Bangladesh in recent years. The middle one has an elevation between (GSB). 0.5m and 1.5m and lower one has an elevation of below 0.5 m located in the south-west part of the study area are 3 Result submerged at the normal flooding condition. Generally In the back swamp zone, the period of inundation is more We compared the relationship between land cover and than three months. This study will provide the updated landform unit and annual rainfall data of the study area. information about geomorphic land form which are related The results of this paper are as follows; to flood protection measure such as embankment The results revealed the relationship between land construction and development of infrastructure and use/land cover change, landform units and annual rainfall preparedness for future flood event. indicate that the built-up area has been expanded on vulnerability with respect to floods. Annual rainfall is 4 Reference closely related to the flood return period regarding to [1] Sayed, M.B. and Haruyama, S. (2015) Dynamics of Land different landform units. A big portion of newly developed Use/Cover Change in , Bangladesh: A Case built up zones are located in the low lying high hazard Study of Manikganj Sadar Upazila. Journal of Geographic Information System, 7, 579-587. zone, especially settlements and commercial activities are http://dx.doi.org/10.4236/jgis.2015.76046 increasing in the recent decades over the low lying agriculture land [1], which put an extra pressure not only