Advances in spatial mapping of waterways

摘要

Substantial advances in Geographic Information Software (GIS) capabilities and improved access to detailed digital elevation models (DEM) produced from LiDAR (Light Detection And Ranging) has improved the quality of waterway mapping which also allows for detailed analysis of waterways over large areas. Studies of waterways over large areas are usually determined from large grid size (20-30 m) DEMs. In this work, a detailed waterway network was created over a 1096 km² area using a 10m DEM. Studies of this type over such a large area are rare because of the lack of suitable raw data and the amount of work and cost required to create and process the data. The motivation for this work came from a requirement of the Ipswich City Council (ICC) for an upgraded stream ordered waterway network to support their vision for healthier waterways within the city (Kavanagh, 2009). The new high quality stream ordered waterway network enables the identification and prioritisation of riparian corridor management activities along waterways and facilitates the monitoring and improvement of water quality.The paper compares waterways from a 20m DEM created in 2004 derived from 5m contours with waterways created from a more accurate and comprehensive 10m DEM created in 2012 from LiDAR data. The study included an assessment of the DEM data and variable parameters such as the most suitable grid scale and catchment input resolution to understand variations in the formation of the waterway networks. Results indicate an approximate 20% increase in lengths of waterways with the new LiDAR based waterways. When compared with the 2004 digital waterways, the additional waterway lengths have the potential impact significantly on cost of remediation of waterways and potentially on the results of water quality modelling. The work illustrated that, in an area such as the ICC, improved waterways created from LiDAR data are suitable for use on a whole of local government authority basis, albeit with a requirement for two stream ordered networks. One network for general waterways locations and lengths, and another more detailed, network for assessment of runoffs and flood studies.