Integrating Information at State, Regional and Local Scales

Watersheds are landscape mosaics; therefore, watershed structure and function is dependent on scale. Temporal and spatial scales influence the inferences we can make about landscape patterns and processes. Spatial scale is the dimension of an object or process characterized by both grain and extent. Grain is defined as the finest level of spatial resolution possible with a given data set and extent is the size of a study area. The scale at which watershed measurements are taken influences our ability to detect spatial patterns. Biotic and abiotic processes vary in their operating scale.For example, anadromous fish are affected by stream and ocean environments. In contrast, native minnows are influenced by processes that occur within a stream or tributary.

People’s objectives set the working scale of a project, which in turn influences the type of digital data that will be useful to meet the objectives of the project. For example, the state water quality control board is interested in hydrological data statewide. Though land owners may work at the local level to stabilize stream banks to prevent erosion, geographic information systems (GIS), a computer mapping and analysis tool, can help integrate the physical and biological information from various scales that is relevant to watershed management, restoration, and monitoring. Digital geographic data used in assembling a GIS come in a variety of accuracies and scales,ranging from aerial photography at 1:200 to satellite imagery at 1:1,000,000.Clearly, there is a role for data at all scales. Currently, however, digital data is almost exclusively restricted to the global scale (1:80,000 – 1:1,000,000),leaving many local projects without large-scale, local data.

A Case Study: Parsons Creek, A Russian River Tributary

Parson’s creek is a minor tributary of the Russian River, which runs through the University of California’s Hopland Research and Extension Center.The creek becomes almost dry in summer and can exceed several hundred cubic feet per second in winter. Historically, the creek supported a significant steelhead population. However, today the population is greatly reduced.The creek is affected by grazing, roads, and development. Gravel removal and channel alteration was conducted in the 1950s and the creek was severely altered by a 1964 flood. Because of these human-induced and natural disturbances,the creek channel has eroded deeper and wider and the riparian vegetation has been severely damaged. Continued grazing, browsing, and seasonal movement of bed load have prevented plant regeneration. This habitat alteration is typical of many tributaries of the Russian River.

Hopland Research and Extension Center Staff began the Parson’s Creek Project to protect and restore habitat for anadramous fishes along a portion of the Creek. The long-term goal is to increase streambed stability and shade canopy throughout the watershed. This will require cooperation among several landowners. We are using the Parson’s Creek watershed as a case study of the use of GIS data for studying watersheds to assist the landowners in prioritizing and monitoring their efforts. We have identified data from many sources, including hydrology, pasture boundaries, partial stream data from Global Positioning System (GPS), elevation, Klamath Bioregion vegetation classification, and California Department of Forestry’s hardwood pixel data.These layers provided the opportunity to correlate mapped vegetation types with vegetation data in the field. The classified satellite imagery is too small in scale to meet the objectives of the project. Large-scale aerial photography, combined with ground-truthing, can provide better information on riparian vegetation than small scale satellite imagery.

Hydrology Digital Line Graphs do not match well with the actual location of Parson’s Creek as measured using GPS. In some locations, the two streamlines are as much as 63 meters apart. This is a problem of scale, because the GPS data has a rated accuracy of approximately 3 to 5 meters, whereas the hydrology data was digitized for maps intended to be reproduced at a 1:100,000 scale. This discrepancy illustrates the inherent difficulties of integrating small, linear features such as streams and riparian areas in a GIS. In fact, we found that walking the stream with a GPS unit is the most accurate way to map the stream channel.

Conclusions

GIS provide a format for integrating data that has been mapped at different scales and varying resolutions. However, numerous circumstances still prevent available digital data from being useful. These circumstances include technical difficulties inherent in integrating data from different sources and extrapolating from data with a given grain and extent to another area with different dimensions.The solution to these problems often requires establishing uniform standards for future digital data sets and extensive documentation of the meta-data.Adopting this policy will help with some of the technical difficulties of integrating data, but this will not solve the entire problem.

Economic, political, and bureaucratic problems prevent access to and integration of local, regional, and statewide efforts. Theoretically, large-scale and local GIS efforts could be linked to region-wide coverages, thereby permitting the extrapolation of information from among small watershed projects.Ideally, small- scale data should be used to prioritize local watershed conservation and restoration efforts. These projects should then have access to large-scale information. Access to both scales of data can make a difference in watershed planning, project implementation, and monitoring.

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Adina M. Merenlender
Colin Brooks
Integrated Hardwood RangeManagement Program, Hopland Research and Extension Center

prepared and edited by Richard B. Standiford and Pamela Tinnin