Elevation Data for Floodplain Mapping

Elevation Data for Floodplain Mapping
Author: National Research Council
Publisher: National Academies Press
Total Pages: 166
Release: 2007-08-16
Genre: Science
ISBN: 0309185556
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Floodplain maps serve as the basis for determining whether homes or buildings require flood insurance under the National Flood Insurance Program run by the Federal Emergency Management Agency (FEMA). Approximately $650 billion in insured assets are now covered under the program. FEMA is modernizing floodplain maps to better serve the program. However, concerns have been raised as to the adequacy of the base map information available to support floodplain map modernization. Elevation Data for Floodplain Mapping shows that there is sufficient two-dimensional base map imagery to meet FEMA's flood map modernization goals, but that the three-dimensional base elevation data that are needed to determine whether a building should have flood insurance are not adequate. This book makes recommendations for a new national digital elevation data collection program to redress the inadequacy. Policy makers; property insurance professionals; federal, local, and state governments; and others concerned with natural disaster prevention and preparedness will find this book of interest.

Flood Hydrology

Flood Hydrology
Author: Vijay Singh
Publisher: Springer Science & Business Media
Total Pages: 450
Release: 1987-09-30
Genre: Science
ISBN: 9789027725745
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Floods constitute a persistent and serious problem throughout the United States and many other parts of the world. They are responsible for losses amounting to billions of dollars and scores of deaths annually. Virtually all parts of the nation--coastal, moun tainous and rural--are affected by them. Two aspects of the problem of flooding that have long been topics of scientific inquiry are flood frequency and risk analyses. Many new, even improved, tech niques have recently been developed for performing these analyses. Nevertheless, actual experience points out that the frequency of say a 100-year flood, in lieu of being encountered on the average once in one hundred years, may be as little as once in 25 years. It is therefore appropriate to pause and ask where we are, where we are going and where we ought to be going with regard to the technology of flood frequency and risk analyses. One way to address these ques tions is to provide a forum where people from all quarters of the world can assemble, discuss and share their experience and expertise pertaining to flood frequency and risk analyses. This is what con stituted the motivation for organizing the International Symposium on Flood Frequency and Risk Analyses held May 14-17, 1986, at Louisiana State University, Baton Rouge, Louisiana.

Assessing the Resolution Effects of Digital Elevation Models on Automated Floodplain Delineation

Assessing the Resolution Effects of Digital Elevation Models on Automated Floodplain Delineation
Author: Richard Charrier
Publisher:
Total Pages: 118
Release: 2009
Genre: Digital mapping
ISBN:
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Automated floodplain modeling commonly requires Digital Elevation Models (DEMs) to represent the topography. As a raster representation of the Earth surface, changing a DEMs resolution (data cell size) has a profound impact on the floodplain delineation. Since 1995 DEM resolution has increased from 100- to 1-meter resolution. This thesis addresses how different DEM resolutions, and different DEM data sources, affect the outcome of modeled floodplain boundaries in the Camp Creek Watershed, a predominately agricultural watershed in Missouri. Two data sets are analyzed: a Light Detection and Ranging (LiDAR) terrain model re-sampled to 1-, 3-, 5-, 10-, 15-, and 30-meter resolutions and existing United States Geological Survey (USGS) 5-, 10-, and 30-meter DEMs. The floodplain delineation process includes hydrologic modeling, hydraulic modeling, and floodplain delineation. Each process includes various input parameters and outputs. Resultant stream networks, watershed boundaries, and floodplains are examined to evaluate the effects of different resolutions. Using 3- or 5- meter LiDAR DEMs produces data that agree with the 1-m data greater than the 90th percentile. The agreement also includes the 10-m DEM data when analyses remove the floodplain modeling cumulative discrepancy effects. Similar trends were not found when using the USGS counterparts; possibly due to the use of the same underlying source material to create the DEMs. When removing the cumulative distortion effect of resolution on the entire modeling process, LiDAR DEM floodplains displayed a 1-4% increase in goodness of fit. Analyzing the results of two separate hydraulic models (HEC-RAS and CARES) finds little difference between their calculated flood surface elevations. Additionally, the thesis analyzes the data storage needs and processing time for modeling different resolutions, finding substantial savings in both as the underlying DEM resolution is decreased. The thesis begins to analyze how models are affected by input variables but many additional studies are needed. Further study of these variables is needed to determine if a single most appropriate model and DEM resolution exists, or what combination of models are appropriate for various types of automated floodplain modeling.