i17 Delta Levees Centerlines 2017

In the Delta Anatomy Mapping Project, all levee anatomies were delineated using slope grids built from available LIDAR data points. LIDAR data points were converted to digital elevation models and subsequently into slope grids. Thresholds were identified that capture the levee crown, levee landside, levee waterside, ramps and toe ditches. Visual interpretations of slope thresholds were used in conjunction with heads-up digitizing to maintain smooth boundaries at a scale of 1:550. The delineation thresholds were derived from a combination of mapping scale, slope grid resolution and slope thresholds used for each anatomy classification. All anatomy has gone through internal quality control processes to ensure a minimum accuracy of +/- 3 feet. Once the levee anatomy was created and accepted, the Esri geoprocessing tool "Polygon to Centerline" was used to create a levee crown centerline. From there, the centerlines were merged by LMA, with a single line for each LMA. After the centerlines were accepted and any errors fixed, the centerlines were split by reach and attribute fields (such as project or non-project). This data depicts the levee anatomy at the time of the LiDAR survey (2017) and are only accurate for that time. Users should be aware that temporal changes may have occurred since this data set was created and some parts of this data may no longer represent actual surface conditions. This data is an update to the previous Atlas dataset with Delta Levee Centerlines, derived from the 2007 Delta LiDAR. Processing and digitizing work done by CA DWR, Division of Engineering, Geodetic Branch, Geospatial Data Support Section, specifically by Arina Ushakova (Research Data Analyst I), and initial QC by Joel Dudas (Senior Engineer, Water Resources).