Page 1 of 3 Next  Muhammad Zulkarnain Abd Rahman Department of Remote Sensing Faculty of Geoinformation Science and Engineering Universiti Teknologi Malaysia Dinand Alkema International Institute for Geoinformation Science and Earth Observation (ITC), Enschede, The Netherlands Abstract Recent development in hydrodynamic modelling requires accurate and detailed terrain model. One of the main problems is frequent changes of land use in major cities, where frequent updating of the digital terrain model (DTM) for flood modelling might be needed. This paper presents an example of assessing the impact of developments on changes in flood behaviours in Naga City, the Philippines. The elevation data is constructed through integrating various elevation data derived from many sources. The development impact assessment is implemented by detailed observation on changes in flood hazard areas. The geostatistical approach is used to investigate the effect of integrating multi-sources of elevation data by evaluating the nugget values. Four interpolation methods were used, namely Australian National University's Digital Elevation Model algorithm (ANUDEM), Kriging, Polynomial and Triangulated Irregular Network (TIN). The assessments are based on the Percentile Vertical Accuracy Assessment, error point’s distribution and visual assessment of the DTMs. As a result, the kriging interpolation method has produced the best DTM and it full-filled the requirements for hydrodynamic flood modelling purpose. Two sets of Digital Surface Model (DSM) were constructed to illustrate the situation of Naga City, before and after the developments. The 1D2D SOBEK flood model was used to simulate flood events for 2, 5, 10 and 17.5 years return period flood. Through this study, it was proved that by simply elevating ground terrain only can solve the flood problem in a particular area. Unfortunately, the flood problem is transferred to another area. 1. INTRODUCTION Rapid and uncontrolled urbanization in developing countries has become one of the major issues in flood hazard and risk management. This is certainly one of the major environmental problems in the developing world, today and in the years to come. Inevitably, urbanization has great influence on rainfall runoff and flood behaviour. The flow of the floodwater becomes complex due to complicated buildings distribution and structures in an urban area. Excessive water from heavy rainfall easily converted to run-off over paved surface, and due to improper urbanization planning, water will accumulate and increase the potential of flooding. Thus impose great challenge in forecasting and predicting the potential damages. In most cases, improper development in developing countries might ignore above mentioned impact on flood hazard and risk to the surrounding community. In this case, the 2D flood modeling requires detailed and accurate terrain model, which quality depends on the acquisition techniques and the characteristics of terrain under investigation. The main objective of this research is to generate DTM and DSM of the study area with consideration on current and future developments, followed by simulating the flood events and development impact assessment. 2. STUDY SITE Naga City is located in Bicol region, at the south-eastern tip of the Philippine island of Luzon. Naga City, located about 377 km to the south of Manila, is well known as a fast-growing area (see figure 2.1). Naga City has the largest population among 35 municipalities in Camarines Sur, which population covers about 8.9 percent of the total population of the province (Naga City Government Philippines Business for Social Progress, 2001). Naga is considered the heart of the Bicol region, consists of 27 Barangays on the land of 7,748 hectares. The main portion of The Naga city is located in low and flat topography that usually inundated by flood when water from the Naga and Bicol River overflow. Thus, substantial discharge and heavy rainfall during monsoon commonly causes severe flood in this city.  Figure 2.1: Naga City 3. DATA COLLECTION RESEARCH METHODOLOGY In this research the data collection is divided into 4 major groups as follow.
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