T 5 N R 21 E Milwaukee County

FIGURE 5.7 Example: control summary diagram.

FIGURE 5.8 Example: control survey station recovery sheet.

information system. Such data may include—among a virtually infinite variety of physical, social and economic data—street address, parcel area, ownership, valuation, existing land use, zoning, and presence of such conditions as flood hazard, and environmental contamination. The topographic maps, cadastral maps, and related attribute data should be prepared and maintained in digital format for ready computer manipulation and automated display.

FIGURE 5.10 Typical cadastral map.

FIGURE 5.10 Typical cadastral map.

Flood Hazard Area Mapping

Figure 5.11 illustrates the use of the control survey and mapping system in the delineation of flood hazard areas. The figure illustrates the accuracy and precision with which flood hazard lines can be delineated. It should be noted, however, that the maps also greatly facilitate the conduct of the engineering studies required to delineate the flood hazard areas, particularly the hydrologic and hydraulic studies that provide the flood stage elevations that are projected on the map hypsometry to produce the flood hazard lines. The control survey and mapping system facilitates the delineation of the channel profiles and cross-sections and the conduct of the field surveys necessary to determine bridge and culvert waterway openings and related hydraulic characteristics. The maps permit the accurate delineation of both natural and artificial watershed and drainage boundaries essential to determining drainage areas for use in the hydrologic analyses. It should also be noted that since the map planimetry accurately displays rooftops, driveways, paved parking areas, and street and alley pavements, it permits the accurate determination of the impervious surface areas within a water shed, data useful in determining the C values used in the rational method, and the runoff factors in the SCS-TR55 method used in calculating runoff. The control survey network also facilitates the conduct of any field surveys that might be necessary to validate the flood hazard delineation and to relate such delineation to historic flood events and attendant flood damages.

Wetland Area Mapping

Figure 5.12 illustrates the use of the control survey and mapping system for the delineation of wetland areas. In wetland delineation, an experienced biologist, soil scientist, or specially trained environmental engineer visits the site concerned and marks (stakes) the boundaries of the wetland and associated plant communities and animal habitats in the field. This visit and survey is facilitated by having a copy of the large-scale topographic map of the area concerned in hand. A registered land surveyor then surveys the boundaries as marked, utilizing plane surveying techniques; and then delineates the surveyed boundaries on a plat of survey tied to the control survey network. This permits integration of the resulting wetland maps into the existing base maps and into a parcel-based land information system for the area concerned.

For some environmental reconnaissance surveys and inventories, somewhat cruder survey techniques may be utilized. These could involve the use of commercially available handheld global positioning system instruments that—with an attendant proper software program—can provide State Plane Coordinate locations with an accuracy of about three to five meters. In this manner, the biologist or soil scientist involved can obtain crude coordinates for the wetland boundaries as they are marked in the field. These boundaries can then be plotted on the topographic maps, cadastral maps, or on a combination of the topographic and cadastral maps for use in the environmental engineering effort.

FIGURE 5.11 Example: flood hazard area delineation.

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