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An information framework for a biologically effective Willamette River floodplain

Content last updated in June 2017


The Slices Framework is intended for use in making decisions about conservation and restoration in the Willamette River floodplain. It makes use of distinct spatial units for tracking change in the floodplain. The first of these units are 1 kilometer long slices drawn at right angles to the floodplain, first put forward in the Willamette River Basin Planning Atlas (Ch. 8 pp. 131-147 in Hulse, Gregory and Baker 2002). The second of these units are 100m subdivisions of the original 1 km slices, with ten 100m slices in each 1 km slice.

We provide access to three types of information, each of which uses the slices as a reporting unit for processes and patterns that are critical to native ecosystem function. These three types of information are:

PDF Maps

A set of 20 PDF documents showing slice boundaries and slice numbers superimposed on contemporary air photographs;

Tabular Attribute Data

A spreadsheet that reports amounts of key processes and patterns by slice and how they vary over time;

GIS Data

ArcGIS data (provided as a shapefile and as a geodatabase) that contains similar information as the PDFs and spreadsheet, but in one place and with greater analytic capabilities.

Using the Slices Framework consists of finding the portion of the floodplain you’re interested in and opening the relevant PDFs, spreadsheet, or ArcGIS file that best suits your purposes.

The PDFs are a series of 20 single images, each combining an air photo with taxlot boundaries, major road names and 1 km and 100m slice boundaries and numbers. Together, they cover the entire pragmatic floodplain of the Willamette River. We define the pragmatic floodplain as the zone subject to periodic flooding that is bounded by significant infrastructure (e.g. highways, residential areas, etc.).

The spreadsheet quantifies, for each 100m slice, the amounts of key patterns and processes circa 2010 and projected for circa 2050 by the Pacific Northwest Ecosystem Research Consortium’s Conservation 2050 scenario – used here as a guiding vision for a restored Willamette River floodplain.

The ArcGIS shapefile requires specialized hardware and software to use, but for those with access to those tools, it offers more ways to query and make use of the slices information than the PDFs or spreadsheet.

2-year Inundation Maps and Reports for the Willamette River and Select Tributaries

The attached pdfs include reports and maps for 2-year inundation mapping projects completed on portions of the Willamette River, MF and CF Willamette Rivers, McKenzie River, and the North Santiam, South Santiam, and mainstem Santiam rivers. The reports include a description of inundation mapping methods and caveats, the maps illustrate potential floodplain inundation associated with the 2-year flood.


The Willamette River Basin is a place of remarkable beauty, exceptionally productive farm and forestlands, and is home to more than two thirds of the people who live in Oregon. It also faces many changes; changes some argue are unprecedented since Euro-American settlement in the mid-19th century.

The goal of this portion of the Institute for a Sustainable Environment website is to demonstrate and make accessible a geographic framework for tracking change over space and time in the floodplain of the Willamette River. The information framework seeks to pragmatically integrate the geomorphic and hydrologic processes shaping rivers, the biological communities and processes comprising river ecosystems and the human systems guiding their land and water use trajectories. It is intended to help in making decisions about what ecosystem services to conserve or restore, where best to conserve or restore them, and how proposed conservation or restoration actions may fit into a larger guiding vision of a restored Willamette River floodplain.

In attempting to understand the Willamette River and its floodplain, the floodplain provides the most constant and quantifiable spatial framework for comparing physical, biological, and human characteristics of the river corridor. The river’s channel position, adjacent forests, and land use may all change, but the floodplain (the area historically inundated by floods) is relatively constant.  In short, this framework, oriented on the floodplain axis, provides a consistent basis for comparing changes in geomorphic structure, aquatic ecosystems and human settlement. We employ this framework for floodplain assessment by first mapping one-km “slices” of the floodplain at right angles to the floodplain’s center axis (Hulse et al. 2002; Hulse and Gregory 2004).

We refer to this spatially explicit system for tracking changes in the river and its floodplain as the “Slices Framework”. Within each of the 229 one-km slices, numbered from 0 (zero) starting at the confluence of the Willamette and Columbia Rivers to 229 at the confluence of the Middle and Coast Forks of the Willamette, we subdivide each 1 km slice into ten 100 m slices. Within these 100 m slices we measure and report characteristics that represent the dynamic processes that structure and are structured by the river and its floodplain, and that together capture key relations of ecological dynamism and resilience. In its final form, the framework will include data on channel complexity, floodplain forests, number and location of cold water refuges, native and non-native fish species richness, flood inundation, and the capacity for non-structural flood storage.

Referenced Publications:

D. Hulse, S. Gregory. 2004. Integrating resilience into floodplain restoration. Journal of Urban Ecology. Special Issue on Large-Scale Ecosystem Studies: Emerging trends in urban and regional ecology, vol. 7, pp. 295-314.

D. Hulse, S. Gregory, J. Baker. (Eds). 2002. Willamette River Basin Planning Atlas: Trajectories of environmental and ecological change. (2nd edition), Oregon State University Press, Corvallis, Oregon 97333. p. 180. The Atlas is freely available online as PDF documents.

Technical Details

Technical Detail documents are provided for the phenomena (attributes) associated with each 100 meter or 1 kilometer Slice.  These documents describe data development and processing for Floodplain Forest, Percent Bank Forested, Channel Complexity 2010, Cold Water Refuges, 2yr Flood Inundation, Juvenile Chinook, Native Fish and Conservation 2050 (Floodplain Forest and Channel Complexity).

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