A tool for assisting municipalities in developing riparian shade inventories

Streams in many urbanized watersheds have elevated water temperature, and stream temperature is a regulated aspect of water quality in many parts of the western U.S. Some municipal point source polluters develop temperature mitigation plans that involve compensatory measures linked to stream temperature, principally increasing riparian shade. In this paper we describe a tool designed to help municipalities and other riparian property managers develop inventories of current and potential stream shade. The tool is based on the insolation module of the published model Heat Source to which we made the following modifications: (1) developed user interfaces and regional supporting geospatial data that minimize data acquisition and user expertise requirements; (2) incorporated LiDAR data to produce direct high spatial resolution estimates of riparian vegetation architecture; (3) created a new method to estimate site specific potential vegetation, with concomitant changes in the shading algorithm involving finer discretization and fewer parameter requirements. The new tool produces estimates of existing shade conditions comparable to those derived from on the ground field measurements for small to medium sized streams. We used the tool to develop a riparian shade inventory and a map of potential shade restoration for the City of Albany, Oregon, U.S.A. Results of this case study demonstrate that the tool can help municipalities meet shade reporting and monitoring goals at a minimum cost, including identifying specific areas with highest potential gains in shade. However, the case study identified limitations in some regional GIS framework data that potentially limit broad applicability or increase costs.