A Headwater Drainage Feature Assessment (HDFA)  characterizes the drainage pattern of a property, and is typically applied within the upper reaches of a watershed.  It is a tool that practitioners use to standardize the valuation of first order overland drainage.  In the completion of an HDFA, information relating to volume of water transported, erosion and sedimentation, provision of fish habitat, barriers to fish movement, presence of permanent vegetation communities and groundwater interactions are collected in order to characterize the drainage.  This information is collected multiple times from spring thaw through to mid-summer to ensure that the temporal variation of the drainage is fully understood.  All of these parameters are then jointly considered in determination of sensitivity of the drainage feature, which then provides direction for management of the drainage during proposed development.  Without such assessments, the health of the watershed is at risk of drastically decreasing.  By characterizing the contribution of the first order features, we ensure that permanent drainage features downstream of the subject property continue to receive high quality water with sufficient food and nutrient resources to support the fish community and food chain on which it depends. 

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Visit the Toronto and Region Conservation Authority site at www.trca.on.ca for more information