i03 Delta PrimarySecondary Zones

Delta Primary Zone Boundary The history of the primary zone boundary is as follows: the Primary Zone was defined in the 1992 Delta Flood Protection Act by referring to a map attached to the legislation, on file with the Secretary of State. See Public Resources Code section 29728. The map was submitted by the Delta Protection Commission. It is a large extent (small scale) map, with no real controls, little or no reference marks or guides of any kind, and no legal description. As such, from a mapping point of view, it leaves much to be desired. Nevertheless, by law, this map defines the Primary Zone boundary. Sometime shortly after the law was passed, DWR Land & Right of Way drew the boundary on 24k topo maps which also had the precise, agreed-upon legal Delta boundary. There are some significant differences between the DWR version and the official version. In asking current DWR Land & Right of Way staff (Carrol Leong & Fred Mau), there was no readily-available explanation, and the person who originally conducted it is no longer there. That is unfortunate, because not only are these maps much more "accuracy friendly", but there may have been good reasons why the boundary was drawn as such. This is the Delta primary zone boundary. It was drawn by Joel Dudas on November 27, 2002, as described below. It was drawn at the request of Margit Arambru, Delta Protection Commission. The legal Delta/primary zone effort conducted by Chico State had raised questions about the primary zone boundary, and upon inspection of the issue it has been determined that there is no precise solution available at this time. Lori Clamurro & Margit Arambru indicated that this delineation was acceptable to them upon review (12/8/2002). METHOD: There were significant errors in the paper base map, as evidenced by errors in the locations of roads, watercourses, and the legal Delta boundary itself. Due to these significant problems posed by the errors inherent in the paper base map, the base map was used as a guide, rather than as a literal translation, to locate the primary zone boundary. Furthermore, a second significant assumption was made, namely that the intent of the Primary Zone map was to indicate that the legal boundary and the primary zone boundary are one and the same in many places, but that mapping this would not result in distinguishable lines if they were literally drawn atop each other, and they therefore were lined up adjacent to one another (on the source paper map!), with the gap being as small as possible but also being far enough apart to clearly distinguish the two lines. Therefore, for GIS purposes, the shapefile was created by tracing the legal boundary line wherever this was felt to be appropriate. The third major assumption was that, in places where the primary zone and the legal boundary are separated, the primary zone boundary was equivalent to the primary zone boundary drawn by DWR Land & Right of Way on the higher accuracy 24k maps in all places except where significant deviations obviously occurred as indicated by the official paper base map. The rationale for this is that the 24k map does a better job delineating the boundary according to actual features (watercourses, rec district boundaries, etc.) where the intended boundary was clearly the same, but where the paper map simply cannot represent this intent accurately. However, in places where the intent clearly shows a discrepancy from the "higher accuracy" line, the boundary on the paper base map was literally traced. Delta Secondary Zone Boundary The parent of this file was one of the Delta Vision Status & Trends shapefiles. Published in 4/2007. The change to the boundary near Van Sickle was made subsequent to delivery to DWR on 10/8/2009. Also, offsets versus the legal Delta boundary were corrected by DWR on 10/22/2009. At this time, unless better information becomes available, it is therefore felt that these are the best boundaries available.