KEY PROJECT COMPONENTS:

• Topographic Survey

• High Resolution Ground-Based Laser Imaging

• Prepared Base Map

• Aerial Photography and Mapping

• Hydraulic Cross Sections

• Digital Terrain Model (DTM) 

TVGA was retained to perform a topographic survey of the failure of Tonawanda Creek Road. Heavy amounts of rain created runoff that saturated and weakened the soils that formed the subgrade of Tonawanda Creek Road. On June 25, 2004, the soil under the creekside shoulder began to fail, and by June 27th, a 110-foot-long by approximately 25-foot-wide section of Tonawanda Creek Road had suffered global slope failure. Due to the instability of the soil conditions, TVGA utilized conventional survey methodology combined with the Ilris 3-D laser imaging system to collect the .field data.

The survey included the road failure area and approximately 600 feet each way on Tonawanda Creek Road. The topographic survey included cross-sections of Tonawanda Creek throughout the survey limits, which will be used for future hydraulic analyses. Horizontal datum was referenced to the North American Datum 1983 (NAD 83) and vertical datum was referenced to the National Geodetic Vertical Datum 1929 (NGVD 29). The survey was compatible with the recently completed vectorized base mapping (100-foot scale with two-foot contours) and digital orthophotography of the project completed for the Town of Clarence.

TVGA was able to overlay the newly generated topographic mapping onto the digital orthophotography to determine the magnitude of movement sustained to the area as a result of the failure. TVGA prepared 1”=20’ scale base mapping in AutoCAD and generated cross-sections at 10-foot intervals throughout the project area.