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<br />6.0 DATA COLLECTION AND ANALYSIS <br /> <br />e <br /> <br />6.1 Data Collection <br /> <br />Data required for the LTEC design process can be grouped into the following <br />general categories: <br /> <br />. (1 ) 1 and use <br /> (2) flood plain geometry <br />" <br /> (3) hydrologic and hydraulic <br /> , <br /> (4) geologic <br /> (5) capital costs <br /> (6) t raffi c <br /> (7) repair costs <br /> <br />e <br /> <br />The first category is a new data requirement which could result in a <br />tremendous burden on field survey crews if expedient data collection <br />methods are not developed. Categories 2, 3 and 4 are data presently <br />collected for drainage design. The last three categories of data <br />are generally available in highway agencies but are not traditionally <br />utilized in drainage design; thus, these data are being put to a new use. <br /> <br />The specific requirements and accuracy guidelines for each category are <br />desc ri bed below. <br /> <br />6.1.1 Land Use Data <br /> <br />e <br /> <br />Land use data needs upstream of the crossing include the location and <br />first floor elevation of all buildings and location, area and average ground <br />elevation of all crops. Locations need only be accurate enough to determine <br />where the particular land use is with respect to the cross sections used in <br />the hydraulic analysis and can usually be estimated from a quadrangle <br />map. First floor elevations for buildings should be accurate to the nearest <br />foot. Aerial surveys might suffice for this accuracy since roof elevations <br />can probably be established and a drive-by ground inspection could establish <br />the approximate distance from the roof to the first floor. Other expedient <br />methods of establishing first floor elevations include the use of developers <br />plans or street elevations in conjunction with a drive-by ground inspection <br />to establish approximate distances from the street to the first floors. For <br />example problem A in this manual, field survey crews established first <br />floor elevations to the nearest 0.1 ft, but that accuracy is not warranted <br />in most cases and the added burden on survey crews is likely to introduce a <br />bottleneck in the design process. Ground elevations for crops can be <br />established from aerial survey contour maps. Crop types should be grouped <br />by their sensitivity to incremental flooding. Grain and hay cropland could <br />be treated as one group, while produce cropland would be a separate group. <br />Normally woodland can be ignored in risk analysis. <br /> <br />" <br /> <br />19 <br />