Integrating GIS With GPS for Better
Reservoir Rim Cultural and Natural
Resource Management






Department of Interior
U.S. Bureau of Reclamation
Grand Coulee Power Office

Author
Greg W. Behrens

Greg W. Behrens
Grand Coulee Power Office
P.O. Box 620
Grand Coulee, WA 99133
gbehrens@pn.usbr.gov






ABSTRACT:
Lake Roosevelt was formed with the construction of Grand Coulee Dam in the early 1940's. The reservoir rim encompasses 530 miles of meandering shoreline, of which 70 percent consists of easily eroded unconsolidated sediments. Couple this shoreline with an annual lake level fluctuation of 50-80 feet and landslide activity becomes the norm. Using our GIS database we are able to identify, in the office, those unstable areas which need to be investigated and then easily conduct on-site investigations, guided by our custom marine and land-based GPS equipment.


Lake Roosevelt pre-Historic and Historic Environment

The Columbia River has maintained its course along the general area occupied by Lake Roosevelt, north-central Washington State, throughout historic times. During the Ice Ages, however, the Columbia River was blocked by a large continental ice mass at a point where Grand Coulee Dam now resides. The blockage of this great river created a large lake, Glacial Lake Columbia, which backed up for hundreds of miles and reached depths in excess of 2000 feet. Within this quiescent lake environment were deposited hundreds of feet thick sequences of clays, silts, sands and gravels, along with flood materials derived from many outbursts of the Glacial Lake Missoula Floods. Upon retreat of the continental ice sheets the Columbia River regained its original channel, cutting down through these thick sequences of unconsolidated sediments and leaving hanging terraces which are now quite unstable.

Human adaptation along the Columbia River and the surrounding terraces occurred many thousands of years ago and the archeological finds are a rich part of the cultural history. The creation of Lake Roosevelt inundated many near river cultural sites and the preservation of the remaining sites deserves the utmost attention.

With the construction of Grand Coulee Dam it was required to purchase a 'freeboard' area around the soon to be created Lake Roosevelt. This freeboard area was to provide those lands necessary for reservoir operations and the known fact that much of the reservoir rim would be subject to erosional and landslide activity. The purchase of this needed land was a complicated process and involved two Indian tribes, 6 counties, state highway right of ways, 11 communities, many individuals and other private and public interests. Document and potential landslide areas were also factored into this purchase. The result is a meandering, zig zag and rectilinear boundary of various distances from the high water line.

Lake Roosevelt reached full pool, elevation 1290, during the summer of 1942 and created a shoreline of 530 miles. Since that time the lake cycles through annual fluctuations of up to 80-feet with two historical draw downs which reached 130-feet. Wave erosion coupled with this yearly fluctuation cycle sets up conditions of high bank water storage during the full pool times, and then the unstabling effect of reservoir draw down, triggering reoccurring land slides (Figure 1).

Monitoring of these unstable slopes, and their encroachment onto cultural sites, private and public lands, and the overall degradation of natural resource areas requires considerable efforts of all parties concerned. GIS coupled with GPS is offering an efficient means to monitor those known areas of unstable slopes and better predict and assess those areas which may be facing future encroachment.


Data Creation/Collection

Topographic Maps
In 1974, during the last of the two extreme reservoir drawdowns, an aerial flight was contracted to provide stereo photography of the entire lake at 1:2800 scale and produce one-hundred and sixty 1:4800 scale mylar topographic maps with 10-foot contours. These topographic maps provided excellent base maps upon which to conduct our field mapping (late 1970s, 1980s and 1990s) and also provided bathymetric data to elevation 1160, 130 feet below full pool.
Geologic Data
During the mid to late 1980s and early 1990s extensive field mapping was conducted along the reservoir rim to determine the aerial extent of existing, and potential, slide areas. This data was mapped onto the 1:4800 topographic maps with field notes indexed onto hard copy notebooks.

Government Boundary
During the initial purchase of the lands surrounding the reservoir detailed records of survey were required for the lands transactions. Boundary adjustment have been required since these initial lands purchases and have been entered into the records of survey. These detailed boundary data have been entered into the GIS database through the use of COGO entry. These boundary data provide a very accurate layer which have proven essential for appropriate administrative control and jurisdictional identification. This boundary data should not be used in place of a legal survey because of the ongoing boundary adjustments, continuing shoreline erosion issues, cultural site acquisitions, and other temporal near reservoir conditions.

Digital Topographic Data
The 160 topographic maps created from the 1974 aerial flight provided very high resolution data which were available for inclusion into the GIS database. To accomplish this task it was necessary to scan each of the mylar drawings (Figure 2) and do the necessary conversion in ArcInfo 7.2.1 (AI). The scanned images were registered and rectified in AI Image Integrator, converted into a grid using the imagegrid command and then vectorized using the gridline command. Once the vectorized files were created it was necessary to bring them into Arcedit and clean up the congested areas where contour lines 'bled' together, remove roads, fence lines, power lines, etc., and generally clean up and label the remaining contour lines. Each sheet was then edge matched to its adjacent sheet. Due to the large data size of each resulting coverage it was unmanageable to combine more than 5 to 7 coverages together and it was realized that one complete high resolution topographic map of the reservoir would be unobtainable. We decided to create only a complete reservoir map of contour data from full pool elevation, elevation 1290, down to the lowest elevation of data available, elevation 1160. This provided 130 feet of bathymetric data. A portion of this bathymetric data is illustrated in Figure 3.

Digital Geologic Data
As mentioned earlier the entire reservoir was field mapped during the 1980s and 1990s and these data were drawn on paper copies of the 1:4800 topographic maps. Also included on these maps were many sections of shoreline which had erosion rates calculated through photo interpretation. These maps were scanned, registered and rectified using the same method used for the topographic maps. Once the maps were converted into rectified images the geologic information and calculated erosion rates were digitized into their pertinent coverages using on-screen digitizing.

Digital Orthophoto QuarterQuads
The digital imagery used to assist in the field work are the standard U.S.G.S. Digital Orthophoto Quarter Quads (DOQQs) purchased from the U.S.G.S. These DOQQs are becoming somewhat dated since they were derived from a 1991 data collection effort but they are still useful for many purposes.

Digital RasterGraphics
The U.S.G.S. produces and sells scanned images of their 7 «-minute topographic maps. These digital raster graphics (DRGs) are also available commercially from many vendors who have removed the border/collar information from these scanned images. All of the Digital Raster Graphics (DRGs) within the Lake Roosevelt area were purchased in collarless format for the ease in tiling them together and overlay of data.


GPS Chart Plotter and Custom Electronic Navigation Chart

Since much of the investigation along Lake Roosevelt requires the use of a boat we realized that a marine type GPS navigation system would be the best designed unit for this effort. A Raytheon Raychart 620 was purchased for the chart plotter because of its large chart display and ease of use. A Raytheon Raystar 114 differential GPS receiver was selected because of its differential capabilities and compatibility with the Raychart 620 (Figure 4). With the removal of the Selective Availability from the GPS signal the added cost of differential capability may not be warranted for some GIS applications. Commercially available electronic navigation charts are available for the inland waters of Washington but the scale and resolution of these charts are not suitable for reservoir rim mapping and resource inventory control. C-MAP USA Inc., of Mashpee, Massachusetts, makes electronic charts which are compatible with many different brands of GPS chart plotters and they also produce an electronic chart for Lake Roosevelt. C-MAP, Inc., was approached to design a custom electronic chart map, using bathymetric data, landslide locations and boundary data derived from the Grand Coulee Power Office's GIS data set . The set of conditions outlining the project's goals were described and the data sets (contour, landslide polygons and boundary) were explained to C-MAP and they graciously agreed to customize an electronic chart map (Figure 5) utilizing this data. This allowed the use of a commercially available GPS chart plotter and GPS receiver which was compatible with a C-MAP NT c-card.


Portable GIS/GPS Platform

The marine type GPS chart plotter with the custom electronic navigation chart works out very well for navigation, bathymetric review and site location while conducting 'on the water' investigation (Figure 6). To assist the 'on shore' investigations of landslides, cultural sites, boundary encroachments and other resource management activities it was desirable to have the capability to carry a portable GIS/GPS unit. The platform selected for this application was a Fujitsu Stylistic 2300 pen tablet computer (Figure 7), capable of running ArcView with the Tracking Analyst extension, and the Raytheon 114 differential GPS receiver. Utilizing the Raytheon GPS receiver negated the necessity to purchase another GPS unit for the pen tablet. Because of the dedicated GPS receiver/chart plotter plug and receptacle it was required to make a junction box which would allow the GPS unit to be connected with an external 12 volt power supply and a separate RS-232 data cable for data transmission to the pen tablet.
Using the pen tablet computer system with its GIS/GPS capability allows the utilization of all the DOQQs, DRGs, boundary data, cultural and natural resource data, bathymetric and topographic data, etc, in the field. This creates the ability to conduct realtime mapping of natural and cultural resources, landslide scarps, encroachments, wildlife habitats, etc. All of this data are then readily available for uploading into an office based GIS projects.


Conclusion
The Grand Coulee Power Office has been very pleased with the operation of the GPS chart plotter and the customized C-MAP NT electronic navigational chart. The summer of 2000 will be the first full field season for utilizing the capabilities of this system and everything looks quite promising.

Other benefits of a customized electronic navigation chart for a reservoir such as Lake Roosevelt is the adaptation of the marine GPS unit to the lake's enforcement officer's boats. This allows them to track incidents on the reservoir such as traffic infringements, boating accidents, drownings, etc. It also allows those people unfamiliar with the lake's bottom hazards and shoreline configuration to safely navigate during inclement weather and darkness. Fisheries biologists, limnologists and other environmental researchers can also benefit from this type of unit by being better able to preselect sampling sites based on their known realtime location and lake bottom configuration rather than just using a depth sounder and paper copy navigation charts.