5.5 Sample Field Survey Request

The following is an excerpt from an actual survey request prepared for a flood insurance study on a major river in the State of Illinois. The format of the request may be useful for other similar studies requiring surveyed cross sections for floodplain modeling.

SUBJECT: SURVEY REQUEST FOR CROSS SECTIONS FOR XYZ COUNTY Flood Insurance Study.

The following information is requested for a flood insurance study in XYZ County on the Big River. Right-of-way has not been obtained for any of this work.
The survey information may be obtained by the stadia method. Vertical accuracy of ±0.5 feet and horizontal accuracy of ±5% is acceptable.
Valley sections should be taken at approximate locations indicated on the enclosed maps (not included in this book). These section locations are not absolutely rigid and may be moved upstream or downstream several hundred feet for ease of surveying. The channel portion of these sections as well as the channel only sections shall be at right angles to the channel even though the overbank may not be at a right angle to the channel flow. Conditions along each section, such as direction of flow, channel high bank, fence lines, fields, wooded areas, roads, railroads, etc., should be noted. Section stationing from zero should be included in the field notes and the zero point should be shown on the map. Submitted section stationing should increase from left-to-right looking downstream. Each end of the section should be tied to a prominent structure or ground feature.
Bridge openings should be defined by taking over and under sections, i.e., the length and width of the bridge, the abutment elevations, the low steel elevations, the pier widths and location, the wingwalls, the elevation of the top of parapet walls, a cross section under the bridge, a road or rail profile across the bridge, and any other feature that defines the structure. A sketch of each structure should be included in the survey notes. Also note if the bridge is a perched structure. On road/railroad profiles in which the road/railroad is on fill above the natural ground, take a ground shot of the natural ground adjacent to each road/railroad profile shot.
Sections, bridge openings, and road/railroad profiles are numbered by river mile. They are requested as follows:
BIG RIVER - Requested Cross Sections Description
A. Valley section 50.9: approximately 15,000 ft long from elevation 405.0 ft NGVD in the left overbank to 405.0 ft NGVD in the right overbank, looking downstream.
B. Valley section 55.0: approximately 10,500 feet long from road on left overbank to L & N RR embankment on the right overbank. Do not take soundings of Queen's Lake.
C. Railroad profile and bridge openings (Louisville & Nashville RR) at section 57.1 approximately 13,000 feet long from road intersection on left overbank to road intersection on right overbank.
D. Valley section 59.1: approximately 18,500 ft long from road on left overbank to elevation 410.0 ft NGVD on right overbank. Do not take soundings of Halfmoon Lake.
The data pairs (elevation and station) for each cross section should be delivered as a single file on a high-density floppy disk or CD-ROM in addition to the conventional survey books. The data should be presented in the HEC-RAS input arrangement as shown on the attached sample (not included in this book). The stationing for the data pairs must increase from left-to-right looking downstream and the individual sections in the data file must progress in order from valley section 1.