Building a Digital Model to Protect the City of Nasiriyah from Hydrological Hazards by Using Topographic Survey Methods and GIS

The Digital Elevation Model (DEM) is a representation of the topography of the Earth’s surface and terrain. There are many ways in which the digital elevation model can be obtained, such as the Field Survey and the use of Global Positioning System data, topographic maps and other methods. In this research, a Digital Elevation Model (DEM) has been built dependent on three methods (positioning system—ground survey—topographic maps) in addition to the use of GIS technology to produce high-resolution 3D maps (2 mm) was chosen for application to the city of Nasiriyah, the center of Dhi Qar governorate in the southern Iraq to show the Hydrological hazards on the studied area and the methods of protecting it. It was found that there are many hydrological hazards to the city especially in the winter season such as the erosion of the soil by rain which reached 12.977 tons/ha and the water immersion whose ratio reached to 0.34 cm in some areas. In addition, the study showed that the area is exposed to the danger of flooding in percentages ranging from 0 to 90%, covering 50–60% of the risk of most parts of the study area. Finally, it was concluded that the rise of groundwater levels (0.73 cm) affects on buildings, foundations, soil and infrastructure.