There is no doubt that planning and assessing flood hazards is an essential task in considering sustainable development, in any part of the world. In recent years, the use of GIS has become increasingly popular when mapping and modeling flood predictions and planning accordingly around them. This study focuses on the largest costal city in the world, Varna Bay on the North Bulgarian Black Sea coast. It is estimated that 9% of all European costal zone are below a 5m elevation, leaving these cities extremely vulnerable when considering severe storm surges. Coastal storms on this area of the cost are notorious for being disastrous.
The Bay of Varna has a well developed infrastructure and other urban developments are expanding onto it, however, this expansion is only increasing the possibility of severe flooding to occur due to the depreciation of the land. In order to identify the different areas in the bay that were flood prone, and generate a 3D model, they used many different sources of spatial data, topographic maps in scale 1:50:000, topographic maps in scale 1:5:000, and QuickBird's satellite images procured from Google Earth. The medium scale maps were used to locate the low elevation areas along the cost, the larger scaling maps were used to represent a detailed elevation surface. Then, the topographic maps and satellite images were geo-referenced and edited in ArcInfo to edit out the distortion in the images. Using, GCPs (Ground Control Points) they mapped out easily visible objects--as points of reference. Using a GIS extension they created dynamic 3D models as well as interactive maps. Using 3d Analyst they converted the 2D topographic features from the maps and created a surface called a TIN (Triangular Irregular Network) which are vector based representations of the land. Using the TINs and Xtools pro extension, they were able to look at the low-laying areas and convert them to polygons at different scenarios of sea level rise, at intervals of 1m.
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| Portion of the 3D model created |
This study proved that 14 towns, 17 villages, 13 sea resorts, and 7 small campsites could potentially be devastated by a sea-level rise of 5m--affecting a total of 549,765 residents. This case study is further evidence that using GIS can help with sustainable development and plan for possible catastrophes.
Stanchev, Hirsto. "3D GIS Model for Flood Risk Assessment of Varna Bay Due to Extreme Sea Level Rise." Journal of Coastal Research. no. 2 (2009): 1597-1601. http://www.jstor.org/stable/25738059 (accessed September 22, 2013).
The point that three different maps needed to be used and cross referenced raises an important point about scale in mapping. More, this is a good example of using GIS to map what is and what could be. I wonder, how long it would/will take for the sea to rise 5 m and if the city is acting on these results.
ReplyDeleteSo we can map sea level rise relatively easily, maybe rain flooding, hurricanes/tornadoes, glacial melt?, and a billion other things I'd imagine. I'm wondering where the vulnerable places are that would respond to the information presented to them that haven't been mapped.
ReplyDeleteI'm wondering about how long the process of getting the funding for doing this study, creating the map & the resources needed for doing that, & its potential response that Sarah referred to. I assume that in instances where we know governments won't listen to models there is no mapping being done, or is there?
Are we doing this in the poles? Does it make sense to use this type of 3D modeling where the ice melts so rapidly?
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