###### Abstract  
Mariners navigating within Canadian waters rely on Canadian Hydrographic Service (CHS) navigational charts to safely reach their destinations. To fulfil this need, CHS charts must accurately reflect the current state of Canadian coastal regions. While many coastal regions are stable, others are dynamic and require frequent updates. In order to ensure that important and potentially dangerous changes are reflected in CHS products, the organization, in partnership with the Canadian Space Agency, is exploring coastal change detection through satellite remote sensing (SRS). In this work, CHS examined a hybrid shoreline extraction approach which uses both Synthetic Aperture Radar (SAR) and optical data. The approach was applied for a section of the Mackenzie River, one of Canada's most dynamic river systems. The approach used RADARSAT-2 imagery as its primary information source, due to its high positioning accuracy (5 m horizontal accuracy) and ability to allow for low and high water line charting. Landsat represented the primary optical data source due to its long historical record of Earth observation data. Additional sensors, such as Sentinel-2 and WorldView, were also used where a higher resolution was required. The shoreline extraction process is based on an image segmentation approach that uses both the radar and optical data. Critical information was collected using the automated approach to support chart updates, resulting in reductions to the financial, human and time factors present within the ship-based hydrographic survey techniques traditionally used for chart improvements. The results demonstrate the potential benefit of wide area SRS change detection within dynamic waterways for navigational chart improvements. The work also demonstrates that the approach developed for RADARSAT-2 could be implemented with data from the forthcoming RADARSAT Constellation Mission (RCM), which is critical to ensure project continuity. R ART  
improve the representation of dynamic areas on CHS products and thus improve mariner safety, new approaches must be developed. One example of a dynamic area is the Mackenzie River which is the longest river system in Canada. Flowing from Great Slave Lake to the Arctic Ocean, it covers a distance of approximately 1700 km. It is also the most dynamic water system in the country: in a study area on the Mackenzie valley more than 1800 landslides and other natural terrain hazard features occurred before 2004; this represented an average density of one landslide per 5 km2 [1]. The river also has the highest sediment load of any Canadian river with 100 million tonnes per year (Mt/yr) being transported [2]. Additionally, the Mackenzie River has been the primary marine route for providing supplies to the Western Arctic over the last 100 years. With the increasing development of the oil industry in the Western Arctic, navigation is expected to increase on the river as it represents the main route for transporting heavy freight. Commercial shipping on the river is composed mainly of barges with 1-1.5 m of draft. Two Canadian Coast Guard (CCG) ships, the CCGS Dumit and CCGS Eckaloo, which have drafts of 1.6 and 1.4 m respectively, are used to maintain aids to navigation along the river. Although most ships navigating the river have a small draft with an average of 1.5 m, it remains critical to ensure that safe passage on the river is charted accurately in order to support the safety of navigation. Monitoring changes across Canada's vast waterways using traditional hydrographic surveying techniques is costly and time consuming. Remote sensing provides a practical monitoring tool on local and regional scales to help quantify changes and further enhance modelling and change prediction at different scales for a lower cost [3]. Multispectral imagery is often used to map changes in fluvial morphology and its dynamics as these data benefit from the spectral response contrast of land and water classes in visible, near and mid-infrared bands [4; 5; 6; 7].