Coquille Subbasin Working Atlas
Page 1: Introduction
An Introduction to Available Geographic Information
January, 1996; revised August, 1997
Interrain Pacific (now Ecotrust)
721 NW Ninth Ave, Suite 200, Portland, Oregon 97209
This atlas introduces a sample of some of the geographic information available for the Coquille River Subbasin in Southwest Oregon. It is intended as a learning tool to increase awareness of existing data sources and to develop an understanding of the capabilities and limitations of information technology in using that data.
The atlas was prepared by Interrain Pacific with funding provided by the Coquille Watershed Association through a grant from the Oregon Watershed Health Program. The design and execution of the atlas is the result of a collaborative process involving Interrain Pacific and the Coquille Watershed Association and its members. Interrain Pacific met twice with the Coquille Watershed Association to discuss the nature and limitations of available data and to identify issues and interests to form a foundation for a data analysis strategy. Based on discussions with the Association, Interrain Pacific designed and completed analysis necessary to develop a draft atlas. Interrain Pacific also coordinated data analysis completed by the Oregon State Service Center for GIS, also with funding from the Oregon Watershed Health Program, and utilized previous work completed by the Department of Environmental Quality. Additional technical support was received from other departments of the State of Oregon. The draft atlas was provided to the Coquille Watershed Association and others for review and comment prior to creation of this final version.
The descriptive information on the resources of the Coquille Subbasin provided here is not a complete assessment of conditions within the Coquille. Rather, it is intended as a companion to ongoing assessment and restoration efforts of the Coquille Watershed Association, and as a guide for continued data development and analysis.
Extensive digital geographic information pertinent to the Coquille River area has been developed by a number of public agencies. This atlas includes public information developed or enhanced by the U.S. Geological Survey; U.S. Department of Commerce Bureau of the Census; USDA Bureau of Land Management; Oregon State Service Center for GIS; Oregon State Department of Forestry; and other federal and state agencies. Additional information related to the Coquille River Subbasin is available from these and other federal and state agencies and local governments. Detail on the various data sources used for this atlas are provided in the text and in the summary data table in the back of the document.
While geographic data pertaining to the Coquille is extensive, it is often of a scale that is insufficient for detailed watershed level ecosystem analysis. The more detailed geographic data that does exist is often inconsistent or incomplete across the entire Subbasin. Data inconsistencies and lack of coverage are largely a factor of divided jurisdictions and fragmented ownership and land administration within the Coquille. The subbasin crosses two counties and includes federal land administered by two separate agencies, the Forest Service and the Bureau of Land Management. Despite these limitations, the existing set of data is extensive and useful and forms a foundation of information that can be improved upon over time.
Coquille Watershed Association
The Coquille Watershed Association is a nonprofit group formed to actively engage in the evaluation and restoration of the Coquille River system. The Association is comprised of a broad array of participants with diverse backgrounds and affiliations. The goals of the CWA include defining restoration goals, developing restoration strategies, actively promoting on the ground restoration projects, and providing coordination and administrative support for private landowners participating in restoration activities.
Interrain Pacific is a non-profit organization with a mission to develop public access geographic information systems and promote the capacity of local organizations to use this information technology to address natural resource management issues. Prior to January 1, 1996 Interrain Pacific was known as Pacific GIS.
Oregon State Service Center for GIS
The State Service Center for GIS is part of the Information Resource Management Division of the Oregon Department of Administrative Services. The GIS Service Center acts as a clearinghouse for spatial data for the State of Oregon. A wide variety of human resource and natural resource data are available through the Center. Many data themes are on-line in the spatial data library and may be accessed via the state wide area network (WAN) and the Internet.
The data portrayed in this atlas are actual GIS data of public record. Interrain Pacific makes no claim as to the accuracy of the data and information presented, and has not field verified the data or the hypothetical analyses. No conclusions are implied by the work in this atlas. With proper field verification and broader expert discussion the GIS data used here could be applied as a useful analytical and decision support tool. Interrain Pacific shall not be liable for any activity involving the atlas, including lost profits, lost savings or any other consequential damages, fitness of the atlas for a particular purpose, and other use of the atlas.
Introduction to GIS technology
The maps and related data presented in this atlas were generated using a geographic information system (GIS). Geographic information systems link maps (location data) to databases which describe the attributes of particular locations. This technology greatly facilitates the analysis of complex ideas underlying ecosystem management and assessment because a single operator can quickly search, display, analyze, and model a variety of spatial information.
Ecosystem management requires extensive knowledge of the interrelationships of all the biological, physical, and cultural components of the landscape. The geographic characteristics of these relationships are some of the most critical components of this information. The ability of GIS technology to store, describe, and analyze spatial and temporal relationships enhances the ability to assess ecosystem conditions, design management experiments and advance institutional learning.
Geographic information systems are often mistakenly referred to as computerized maps. This perception belies the true nature and power of this information technology. A geographic information system actually links computerized maps to databases that describe the attributes of particular locations on the maps. The power of GIS technology lies in this linkage. The merger of location and attribute data results in a spatial database that has the capability to answer three basic questions: where is it; what is it; and what is next to it?
The where of a spatial database is the specific location represented through a system of coordinates, such as latitude and longitude. The geographic locations of features in a GIS are often referred to as real-world coordinates because they allow us to fit features of the landscape into their proper position anywhere on the earth.
The what refers to descriptions — or attributes — of features in the landscape, such as a stream, a stand of trees or a stream gauge. These descriptions are often quite detailed and may consist of multiple attributes. For example, the attributes of a section of stream may include the name of the stream, stream class, type of fish present, percentage of gravel, temperature, survey date, etc.
The what is next to it of a spatial database refers to the geographic context of features in the landscape. For example, in a vegetation and land cover database an open field may be adjacent to four different vegetation types: a meadow, a late-successional stand, a 10-year old Douglas-fir stand, and a mixed hardwood stand. The knowledge of these complex relationships is inherent to a GIS database and is known as "topology."
Geographic — or spatial — data are expressed as points, lines, or polygons. Water temperature monitoring sites, towns, or waste disposal sites are identified as points. Roads, streams, pipelines and transmission lines appear as lines. Areas sharing a single characteristic, such as administrative districts, forest types, or homogeneous land use types, are represented as polygons. All landscape features can be reduced to one of these three data categories and recorded as a series of latitude and longitude, or x and y, coordinates. These features are linked to data attributes which describe their characteristics.
Data is generally described in terms of map or data layers; each layer representing a particular set of features. Base map data for a GIS, for example, may include separate layers for roads, streams, soils, elevation, vegetation, and inventory plots.
Spatial analysis refers to asking questions about spatial relationships using a GIS. Spatial analysis questions may range from the simple (e.g. the number of acres within a watershed), to the complex (e.g. the number of acres of mixed hardwood stands within 300 feet of major streams that intersect publicly owned lands on slopes greater than 30% within sub-basins known to support Fall Chinook salmon). Answers to these types of questions can be derived through the analysis of single and multiple data layers using a number of different analysis techniques such as buffering, overlays and network analysis.
Information technology & community capacity
The current state of GIS technology offers many opportunities for advancing local community participation and learning in watershed assessment and resource management. Advances in computer software and hardware have made GIS technology accessible to the general public, both in terms of cost and ease of understanding and use. With minimal orientation and training, the fundamental spatial analysis concepts of GIS can be understood by a wide array of participants. The technology now available through tools such as GIS permits the phrasing of questions that could not be answered even a decade ago. While it is not necessary to become a computer analyst in order to participate in this process, it is important to know enough about spatial analysis ideas to begin to ask challenging questions of the data and the technology.
The opportunities presented by GIS for local participation in ecosystem management lie in the potential of the technology as both an analysis and a communication tool. The compelling visual aspect of GIS provides a unique communication link between the scientific and technical components of research, planning and management on the one hand, and public understanding and participation on the other. Increased accessibility of GIS technology presents a real opportunity to strike a balance between scientific management of natural resources and democratic involvement in decision-making. Moreover, the data and information available through this technology presents opportunities to facilitate dialogue and consensus among a wide array participant with diverse interests and values.
To increase the ability of communities, organizations and individuals to participate fully in natural resource assessment and management processes at the local level, it is necessary to actively build local GIS capacity. Building capacity goes beyond the acquisition of hardware and software. It also includes enhancing the ability of individuals to understand and make use of spatial data by actively promoting awareness of the technology, increasing understanding of spatial data concepts and appropriate uses, developing a common vision for using GIS to understand resource management problems and construct cooperative solutions, and providing access to the data and technology itself.
Area of interest
The area of interest of this atlas is the entire land area draining into the Coquille River along the South Coast of Oregon, referred to here as the Coquille River subbasin. The Coquille River subbasin is part of the South Coast River Basin. This designation is based on the USGS four level hierarchical system for delineating hydrologic units. A hydrologic unit boundary, as defined by the USGS, is a water management boundary which may not always follow the same line as a watershed boundary determined from basin ridge lines. Subbasins are the smallest unit within this system, and are assigned unique eight digit Hydrologic Unit Codes (HUC). Figure 2 shows the location of the Coquille subbasin (in dark gray) along with the other three subbasins of the South Coast basin (outlined in black).
The primary source for the hydrologic unit delineations is the 1:2,500,000 scale USGS national hydrologic unit coverage, although both 1:100,000 hydrography and 1:500,000 Hydrologic Unit manuscripts were also used by the USGS as references. Within the Pacific Northwest Region, individual unit boundaries identified from the 1:2,500,000 scale hydrologic unit coverage were manually re-delineated to capture all of the headwater and lower reach streams of the 1:100,000 hydrography.
|Table 1: Effects of Scale on Road and Stream Data|
Since the scales of the source data for subbasin delineations are relatively coarse, the boundary of the Coquille subbasin is generalized compared to ridge-top delineation at more refined scales (e.g. 1:24,000). Because of this generalized boundary, area totals for the Coquille and its subdivisions may vary slightly from area totals compiled from larger scale source data. Based on the HUC data, for example, the total area of the Coquille subbasin is 1,032.44 square miles. More detailed ridgeline data, however, indicates a total area of 1,039.88 square miles; a difference of less than one percent. The differences in the precision of these two boundary data are illustrated by Figure 3. The HUC data is portrayed in solid gray, along with the more detailed larger scale data in black outline. All analysis and data displayed in this atlas are based on the less detailed HUC boundary since the data was made available to the project already cut to that boundary.
Geographic information varies greatly in terms of accuracy, scale (or resolution), and depth of information. The difference in detail between data of different scales is demonstrated in Table 1. The total miles of streams and roads shown in 1:100,000 USGS data are compared with that shown in larger scale 1:4,800 scale BLM data for the East Fork subdivision of the Coquille.
The types and level of sophistication of a GIS database depends upon the needs of the users. For example, in order to conduct a broad assessment of ecosystem conditions at a basin or subbasin level, it may be desirable to have information regarding roads, population density, broad vegetation types, and slope at a scale of 1:100,000. In order to perform analyses at a project or watershed level, however, more detailed information such as soil series, topography, slope, stand class, and volume per acre by tree diameter may be required at a scale of 1:12,000. The information requirements of these two uses varies in the depth of information needed about the land, the level of accuracy, and in the resolution, or scale, of the information. Because smaller amounts of land area are covered in greater detail, larger scale data is more costly to develop and is typically less available from public sources than smaller scale data.
Very little public data is available for the entire Coquille subbasin at scales greater than 1:100,000, although some data is available at scales of 1:24,000 and even 1:4,800 for portions of the subbasin. Most of the data used in this atlas, therefore, is derived from scales of 1:100,000 or smaller. Some larger scale data (1:4,800) is used in analyses of roads and streams in the East Fork subdivision.