The Use of Photogrammetry and Lidar for Landscape Roughness Estimation in Hydrodynamic Studies

Flooding is a major problem for many countries causing damage to the environment and pressures on human activity. Engineers use Manning’s coefficient of roughness to determine water flow over floodplains which is a vital parameter in hydrodynamic studies. The coefficient is mainly a property of the ground surface texture and the changes in water surface elevation. The traditional method of determining the coefficient requires experience and often demands field visits. Airborne remote sensing provides an opportunity to produce good representations of the ground surface and therefore an easier and more efficient method of determining the coefficient. Digital surface model’s (DSM’s) are standard products from aerial photography and photogrammetry. The introduction of LiDAR technology has provided an alternative method for producing high quality DSM’s. One of the main aims of this research was to assess the potential of using LiDAR and aerial photography/photogrammetry in analysing the landscape for the estimation of the coefficient of roughness. A test site with an excellent variety of features has been established close to Nottingham, UK and DSM’s have been created from LiDAR data and photogrammetry. Analysis of the DSM’s for different types of landscapes has been undertaken. ‘Automated’ techniques for the estimation of the coefficient of roughness have been investigated. Maps of the estimated values of the coefficient for different landscapes have been generated and compared with traditionally derived values for the test site. The research shows that airborne remote sensing has the potential to provide new methods for estimating Manning’s coefficient of roughness (‘n’). * Corresponding author.