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<br />ASFPM Austin 2000 Conference <br />Abstracts & Biographies <br /> <br />An Application of L1DAR Technology in a Flood Insurance Re-Study <br />Project: Brays Bayou - Harris County, Texas <br /> <br />by Shannon Sefcik, E.I.T. and Kenneth L. Sheblak, P.E. <br /> <br />The Federal Emergency Management Agency (FEMA) has initiated a contract with the joint <br />venture of three engineering firms located within the Houston area to perform a re-study of the <br />Brays Bayou watershed Flood Insurance Study, Harris County, Texas. This study has been <br />initiated as a pilot project to be used as a model for additional restudies to be completed in the <br />future. The objectives of the study are: to establish methods, procedures, criteria, and <br />requirements for future studies in areas that are subject to ground subsidence; to produce updated <br />flood hydrologic (HEC-l) and hydraulic (HEC-RAS) modeling data for the watershed; to <br />develop updated floodplain maps based on new topographic data on which the updated hydraulic <br />models are based; and to analyze the effects of inland subsidence on flooding depths in the Brays <br />Bayou watershed. <br /> <br />Current topographic information has been obtained from a vender who has utilized the LIDAR <br />(aerial Light Detecting and Ranging) technology to produce elevation data for the entire Harris <br />County area. The challenges have been to process the large amount of data to determine the <br />appropriate below-tree-canopy elevation for preparation of a digital terrain model (DTM), and to <br />verify the accuracy of the LIDAR-obtained information with traditional and Olobal Positioning <br />System (OPS) field survey measurements. <br /> <br />The current work has shown mixed results for utilizing LIDAR-obtained ground information as a <br />cost-effective, time-saving resource in the preparation of watershed studies. This paper will <br />discuss the implications of ground subsidence with respect to floodplain mapping, the approach <br />taken-for processing the LIDAR-obtained.elevation data into usable true-ground inf.ormation fOI" . <br />the development of a digital terrain model, and the verification process of this information (and <br />its results) using traditional field survey measurements. <br /> <br />Biography: <br /> <br />Shannon Sefcik received her Bachelor of Science degree in Civil Engineering from the <br />University of Houston in May of 1997. Ms. Sefcik is currently registered as an Engineer-In- <br />Training with the State of Texas. Having been employed for three years at the Harris County <br />Flood Control District, she is presently an assistant project manager for the Planning <br />Department. <br /> <br />Page 10 <br />