Abstract:
Flood damage estimation and providing compensation for victims are important post
flood procedures. In Sri Lanka the common practice is to conduct post flood survey and
estimate flood damage. This consumes more time and the collected information may not
be reliable and often questioned by many flood-victims. As a solution, a GIS based flood
damage estimation models is proposed which has been widely used in many flood prone
areas across the globe. Such a system would generate a swift damage estimation and
well organized outputs. The objective of this study is to prepare GIS and Hydrological/
Hydrodynamic based flood damage estimation model for Tawalama area that often
confronts with flood due to overspill of the Gin River. The developed methodology would
be a good resource for the relevant authorities to estimate actual flood damage for future
flood scenarios. The flood catastrophe in May 2003 was recognized as the most disastrous
event during the last century and has been considered for the development of the flooddamage
estimation model.
Available 2003 flood extent which was generated through Hydrological Engineering
Centre (HEC), a public domain software has been used and the flood depths were
extracted by overlaying the topographic layer with the flood extent. Subsequently, an on
site questionnaire survey was conducted to gather damage related information. Floodcompensation
data from Tawalama D.S. office were compared with the flood damage
parameters. Finally depth-damage functions for the flood affected Tawalama area were
developed. The outputs of this study along with inundation duration and flood arrival
time can be used as input data for a Flood Impact Assessment (HEC-FIA) model. The
FIA model can provide structural damage report as individual and aggregated, agriculture
damage report, detailed life loss report and consequence summary report for the area.