Impact of Lidar Nominal Post-spacing on DEM Accuracy and Flood Zone Delineation

Lidar data have become a major source of digital terrain information for use in many applications including hydraulic modeling and flood plane mapping. Based on established relationships between sampling intensity and error, nominal post-spacing likely contributes significantly to the error budget. Post-spacing is also a major cost factor during lidar data collection. This research presents methods for establishing a relationship between nominal post-spacing and its effects on hydraulic modeling for flood zone delineation. Lidar data collected at a low post-spacing (approximately 1 to 2 m) over a piedmont study area in North Carolina was systematically decimated to simulate datasets with sequentially higher post-spacing values. Using extensive first-order ground survey information, the accuracy of each DEM derived from these lidar datasets was assessed and reported. Hydraulic analyses were performed utilizing standard engineering practices and modeling software (HEC-RAS). All input variables were held constant in each model run except for the topographic information from the decimated lidar datasets. The results were compared to a hydraulic analysis performed on the un-decimated reference dataset. The sensitivity of the primary model outputs to the variation in nominal post-spacing is reported. The results indicate that base flood elevation does not statistically change over the post-spacing values tested. Conversely, flood zone boundary mapping was found to be sensitive to variations in post-spacing.

[1]  Håvard Tveite,et al.  An accuracy assessment method for geographical line data sets based on buffering , 1999, Int. J. Geogr. Inf. Sci..

[2]  P. Bates,et al.  Integration of high-resolution topographic data with floodplain flow models. , 2000 .

[3]  J. R. Jensen.  Remote Sensing of the Environment: An Earth Resource Perspective , 2000 .

[4]  B. Mandelbrot.  How Long Is the Coast of Britain ? , 2002 .

[5]  M. Hodgson,et al.  An evaluation of LIDAR- and IFSAR-derived digital elevation models in leaf-on conditions with USGS Level 1 and Level 2 DEMs , 2003 .

[6]  Michael E. Hodgson,et al.  A GIS-ASSISTED RAIL CONSTRUCTION ECONOMETRIC MODEL THAT INCORPORATES LIDAR DATA , 2000 .

[7]  S. Levin.  THE PROBLEM OF PATTERN AND SCALE IN ECOLOGY , 1992 .

[8]  J. A. Tullis,et al.  An Evaluation of Lidar-derived Elevation and Terrain Slope in Leaf-off Conditions , 2005 .

[9]  J. R. Jensen,et al.  Creation of digital terrain models using an adaptive lidar vegetation point removal process , 2002 .

[10]  MICHAEL F. GOODCHILD,et al.  A Simple Positional Accuracy Measure for Linear Features , 1997, Int. J. Geogr. Inf. Sci..

[11]  B. Mandelbrot.  How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension , 1967, Science.

[12]  A S Fotheringham,et al.  The Modifiable Areal Unit Problem in Multivariate Statistical Analysis , 1991 .

[13]  Eric F. Wood,et al.  Effects of Digital Elevation Model Accuracy on Hydrologic Predictions , 2000 .

[14]  Steven M. Manson,et al.  Decision Making and Uncertainty: Bayesian Analysis of Potential Flood Heights , 2002 .

[15]  A. MacEachren,et al.  Sampling and Isometric Mapping of Continuous Geographic Surfaces , 1987 .

[16]  D. Mason,et al.  Image processing of airborne scanning laser altimetry data for improved river flood modelling , 2001 .

[17]  M. Hodgson,et al.  Accuracy of Airborne Lidar-Derived Elevation: Empirical Assessment and Error Budget , 2004 .

[18]  Michael E. Hodgson,et al.  A Parameterization Model for Transportation Feature Extraction , 2004 .

[19]  M. Goodchild,et al.  Scale in Remote Sensing and GIS , 2023 .

[20]  P. Bolstad,et al.  An evaluation of DEM accuracy: elevation, slope, and aspect , 1994 .

[21]  G. Tasker,et al.  Estimating the magnitude and frequency of floods in rural basins of North Carolina , 1999 .

[22]  S. Levin.  The problem of pattern and scale in ecology , 1992 .

[23]  Alan K. Zundel,et al.  IMPACT OF VARIED DATA RESOLUTION ON HYDRAULIC MODELING AND FLOODPLAIN DELINEATION 1 , 2003 .