A Comprehensive Inventory of the Number of Modified Stream Channels in the State of Minnesota. Data, Information and Knowledge Management.

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1 A Comprehensive Inventory of the Number of Modified Stream Channels in the State of Minnesota Data, Information and Knowledge Management Glenn Skuta Environmental Analysis and Outcomes Division Minnesota Pollution Control Agency (651) State of Minnesota Project Initiation Date: April 2011 Project Completion Date: June 2013

2 Executive Summary Minnesota is home to nearly 90,000 miles of streams and rivers, which for over 160 years have been modified, redirected and rerouted to accommodate human development and entrepreneurship. To increase agricultural capacity, increase land value and improve infrastructure construction, many modifications have been made to the Minnesota landscape to drain wetlands, hasten water runoff and control stream flows. Despite these dramatic alternations to the landscape, there has been no comprehensive national or statewide effort to catalogue these landscape modifications. Understanding the true extent of stream alternations provides a critical baseline for knowing what was lost and what may be possibly restores. There is no single dataset in Minnesota cataloguing altered stream channels. Previous estimates known to be incomplete and outdated underestimated the extent of stream and river channel modification in Minnesota to be between 15 and 30%. This project was a concerted effort between the Minnesota Pollution Control Agency (MPCA) and Minnesota Geospatial Information Office (MnGeo) to create a statewide inventory of streams that have been hydrologically modified (e.g. channelized, ditched or impounded). Created in support of the MPCA s water quality monitoring and assessment program, this data provides information about stream habitats that have been compromised through such alteration. The project visually reviewed the records of approximately 105,000 miles of streams and classified streams into four major categories: 1) Natural, 2) Altered, 3) Impounded, and 4) No definable channel. A detailed decision tree approach was developed and implemented, using a number of geographic datasets. These datasets ran a represent a diverse cross-section of resources, including 30 years worth of satellite imagery, national wetlands inventory, digital raster graphic, air photos dating back to the early 1930s and 3 meter resolution LiDAR imagery.

3 Description of the business problem and solution Although known as the Land of 10,000 Lakes, Minnesota is also rich with rivers and streams. Nearly 90,000 miles of these freshwater resources cross Minnesota, including the headwaters of the Mississippi River. The state is also a vital agricultural area, and many streams and rivers have been altered to improve agricultural productivity. In the Twin Cities metropolitan area and other urban areas, streams and rivers have been altered to facilitate residential and commercial development. The extent of these hydrological modifications was unknown prior to this project. Estimates of the number of streams that had been modified were based on outdated and spatially limited information. The four images below provide an example of one type of stream channel modification from an unnamed stream in South Central Minnesota. The image on the bottom right provides an example of the inaccuracies with the existing stream trace dataset. Lacking a set common set of comprehensive data indicating where streams may have been modified, prior to the project MPCA staff used multiple tactics and data sources to determine whether a stream was altered. This process that was often time consuming,

4 subjective and did not provide consistent results due to different possible ways to interpret the data. Solution To develop a comprehensive inventory of hydrologic modifications to streams in Minnesota, the MPCA entered into an inter-agency agreement with the Minnesota Geospatial Information Office (MnGeo), a program unit of MN.IT Services. MPCA and MnGEO worked together to Develop a methodology for determining stream channel modifications using existing geographic information system (Esri s ArcGIS) software and reference layers. The methodology focused on visual interpretation of contemporary and historic aerial imagery, as well as several other reference layers. The project developed a process whereby each stream segment (down to 150 meter scale) was assigned a status of natural, altered, impounded or no definable channel. The evidence used to designate each stream segment was identified and a code of high, moderate or low confidence and was assigned to each delineation based on the evidence that was used to make the decision. As part of the methodology development a drop-down data driven toolbar was developed in VB.NET to complement the hydro event management tool (HEM) in Esri s ArcMap software. Additionally, a Python script was developed in the ArcGIS environment to identify combinations of criteria and delineation types that were not compatible with the methodology. The drop-down toolbar and Python script streamlined data entry and provided quality assurance for each delineation. Because this project was driven on visual interpretation of information, an additional quality control phase was developed specifically to determine if different individuals using the same reference layers came to similar conclusions. This analysis provided reassurance of existing delineations as well as identified critical decisions that needed additional criteria during method development. Significance of the Project The results of this project represent the first comprehensive attempt to document the extent of stream channel modifications in the state of Minnesota, and to our knowledge, represent the first effort nationwide. This information provides the public with an accurate understanding of the extent of stream channel modifications throughout the state and provides a baseline to understand further modification. This project also developed a stand-alone method which other states or private entities may adapt to

5 develop similar datasets for specific projects. Finally, the project identified inaccuracies within the stream path dataset that could be used to guide updates in future efforts.

6 Benefits of the Project The project developed a method for realizing a comprehensive understanding of a statewide stream channel conditions for the first time. The information is a valuable resource for water managers, environmental scientists, urban developers and other stakeholders who are interested in understanding the relationship between stream alteration and stream habitat, hydrology, connectivity, water chemistry and aquatic life. This dataset has streamlined many aspects of the MPCA s watershed assessment initiative and will act as a foundation for the expansion of new assessment tools. In addition, the outcomes of this project have supported many other projects within the agency, other state agencies and external partners. The results of this project have been made available through an interactive web-based mapping tool and through a data download link on the project s webpage. The total cost of this project was $474, This project was funded with monies from the Minnesota Clean Water, Land and Legacy Amendment.