Relative Stable Area 



Erosional Area 



Level 



Figure 3. 



Schematic of profile line showing relative location of TBM 

 and instrument stake. 



A second wooden stake 1.5 feet (0.5 meter) long should be placed online and 

 10 feet (3 meters) seaward of the TBM. This stake is used during each survey 

 to locate the instrument online and in approximately the same place. The ground 

 elevation of this point should be at least 5 feet less than the maximum length of 

 the level rod to allow the profile to be surveyed to the elevation datum without 

 requiring turning points. During each survey, the actual instrument height and 

 location are determined from direct measurement to the TBM using the level rod 

 as a tape to measure the distance. Thus, only direct measurements (no stadia) 

 are used to locate the instrument. These two stakes have the added benefit of 

 indicating profile azimuth. 



For consistency and ease of later analysis, each survey should begin at the 

 same point and cover a part of the profile that will remain stable during the 

 life of the study. Additionally, one survey (preferably the first one) should 

 extend sufficiently landward to provide a reference profile in the event of 

 erosion reaching the TBM. 



IV. SURVEY PROCEDURE 



The survey crew includes a rod person (RP) and an instrument person (IP) . 

 The RP is responsible for holding the level rod and for selecting the points 

 to be surveyed. The IP makes the measurements and records the data. 



1. Instrument . 



The IP positions the instrument over the instrument stake. Exact posi- 

 tioning is not critical since the actual distance from the instrument to the 

 TBM will be measured. The RP places the range pole next to the TBM and extends 

 the level rod as needed. An additional range pole can be placed at the profile 

 monument if needed to better define the profile azimuth. 



10 



