Development of distributed models for storm surge damage assessments using Remote Sensing generated parameters: Evaluation for Orissa supper cyclone case
Subashisa Dutta, M. Chakraborty, S. Panigraphy Agriculture Resource Group, Space Applications Centre, Ahmedabad - 380 015 A storm surge formed by a tropical cyclone along the seacoast, moves into the land surface in the form of giant tidal waves as high as 5-10m and causes heavy damage on its way. The intensity and spatial distribution of a storm surge depend upon the cyclone properties such as wind speed, low pressure at the centre of the cyclone, wind direction etc as well as the coastal properties such as bathymetric, shape, vegetation lining and presence of esturian region. Most of models including all the parameters are limited to use in practical applications such as disaster mitigation, damage assessment etc due to non-availability of the storm's characteristics in time. The recent Super Cyclone of October 29, 1999, in Orissa state, that induced the worst storm surge leaving thousands dead is an example even after two days of storm surge, no relief or rescue measures could be reached to hundreds of marooned villages. Since our aim was to develop a practical model for damage assessment, a simplified one-dimensional quasi0steady profile based approach is purposed to determine the highest resultant fluid force at any point on the land surface. This resultant fluid force, which is sum of static and dynamic force extracted at that point by the surge wave, may be assumed to directly proportional to the damage caused by the surge. One dimensional energy balance equation may be used to compute the highest resultant fluid force along a computational strip, including the frictional resistance of the landcover as frictional loss component in the equation. Two distributed models using the above principle have been developed in C program and used GIS software ARC/INFO for input data preparation and display of output. The difference between these models is that available surge parameters are given to the model. The Reverse model (RM), which requires the farthest line in land surface effected by the surge, calculates the total pressure by pixels from the farthest to the seacoast, and finally, provides the spatial damage index map. The Forward Model (FM) similarly computes in reverse direction the total pressure by pixels using input parameters such as maximum wave height, location of hit and lateral variation along the coast of the storm. These inputs were predicted with available analytical method using meteorological, satellite and bathymetric data. In the super cyclone case, digital elevation model, coastline and the drainage pattern of river Devi of Jagatsinghpur district, were prepared from the SOI toposheets. The critical input parameter as the line of furthest effected was derived from RADARSAT data acquired on Nov 2 which incorporated into the FM. Similarly, the frictional resistance map was prepared from IRS 1D LISS III data of 16th Oct, 99. The damage maps obtained from these models were compared with point observations made during the field visit. The results obtained from these models are encouraging. So, the models can be utilized for disaster mitigation, damage assessment, coastal zone management etc. | ||
|
|