Development of an Urban Forest Canopy Model for input into a Lidar-based Stormwater Runoff Model for Halifax Harbour Watersheds.

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A major challenge from a changing climate in Atlantic Canada is anticipated to be an increase in the intensity and frequency of extreme weather events, such as storms and associated precipitation. Amplification of extreme precipitation amounts could overwhelm conventional storm water systems and so require adaptive measures. As part of its climate adaptation program, HRM is carrying out a three year project to create a hydrological systems model of the Halifax Harbour drainage basin. The intention is to build a LiDAR-based GIS model of the Halifax Harbour drainage basin in order to model urban storm water runoff for future development under different climate change scenarios. This will allow HRM to better plan future development to be more resilient to a changing climate. Natural vegetation in a watershed has the capacity to influence storm water flow rates. As such, there is a need to consider both the inclusion, and removal of forest canopy, in the quantitative assessments and prediction of runoff from HRM watersheds. The overall HRM hydrological systems model needs to incorporate quantitative assessments of the impacts of urban forest canopy on runoff. There was therefore a need to develop a LiDAR-based modeling approach by which the extent of forest canopy in designated watersheds, and the associated runoff could be incorporated into the HRM hydrological systems model., To analyze existing LiDAR data for a representative portion of the Halifax Harbour drainage basis in order to classify vegetation and create a Canopy Height Model (CHM) of the urban forest. To develop a model that calculates the water retention potential of the urban forest canopy and resultant flows of water with, and without, the mitigative benefits of the canopy. To use the findings as a sub-component of the Halifax Harbour hydrological systems model., A final written report outlining the project methods and results. Metadata and associated GIS data on HRM urban forest., There will be improved capability to quantify the extent of urban forest in all of the HRM watersheds, as well as assess the potential impacts of forest management options on hydrology and flooding. The methodology developed will be used by HRM (and potentially other municipalities in the future) to analyse the remainder of the Halifax Harbour drainage basin and possibly other parts of the municipality. It is envisaged that this methodology will also become part of a wider set of guidelines/tools to help municipalities conduct more accurate storm water vulnerability assessments and more strategic adaptation plans for afforested watersheds.