Abstracts

Using LiDAR to Map Floodrisk: Examples for Coastal & River Flooding

Emergency management personnel and land use planners require accurate maps of flood risk along the coast from storm surge events and long-term sea-level rise and also along river floodplains. Two approaches hav been taken to generate flood risk maps for these two environments. Standard GIS programming has been used to develop a tool to map flood inundation due to increased coastal water levels using LiDAR surface models. The tool has been applied to several coastal areas around the Maritimes. Storm flood uses the LiDAR derived DEM as a base and calculates the area of inundation assuming a still water level and ensures connectivity so that low lying inland areas that do not have free connection to the ocean are not inundated. Once the areas of inundation are determined for a given water level, the recurrence intervals, or probability, of that water level are determined using Water Modeler, a new tool that has been developed at AGRG that uses the time series of local tide gauge records to calculate recurrence intervals. Changes in sea level associated eustatic conditions from climate change and local crustal motion can be incorporated into the software to calculate the return period of a water level in the future under these conditions. For river floodplain inundation in the Oxford, NS area, a series of river cross-sections derived from a LIDAR DEM and river flow estimates have been used with HEC-HMS and HEC-RAS to model flooding. Hydrologic modelling tools such as HEC-RAS do not check for connectivity to source waters (ie. river channel) and as result low-lying areas within the floodplain are inundated without connection to the channel. This suite of tools provides Geomatics professionals with an inexpensive and effective way to map risk associated with storms surge events and river flooding.