Communities cooperating for land and water conservation
The Green Banks: Clear Waters program will improve our knowledge of riparian area health. This information will be used to increase awareness among local residents and to target the delivery of projects that protect watersheds and water quality. Benefits will be felt both locally and within the greater Lake Winnipeg Watershed.
The Manitoba Habitat Heritage Corporation has initiated this riparian-focused program in partnership with four conservation districts (CDs). It is designed to complement the Integrated Watershed Management Plans that each of these conservation districts have developed. Cooperating conservation districts:
Riparian Vegetation Classification
At the root of this program is the detailed classification of riparian vegetation. The type and extent of vegetation is very important for the health of these zones – e.g. for stabilizing stream banks and filtering runoff. However, this information is not widely available. Through this program, riparian vegetation along twelve streams will be classified using specialized computer software and detailed aerial photographs. Riparian land cover maps will be generated for these priority waterways within the partnering conservation districts.
Distinct patches of vegetation can be seen on high-resolution ortho-imagery (air photos), such as tree groves, meadows or cultivated fields. These air photos are in colour and have a resolution of 0.5 to 1m. Based on colour and shape, specialized software groups the pixels that represent these patches into separate units, or unique polygons. The software then classifies these units into 9 different vegetation and land cover types. Agriculture and Agri-Food Canada – Agri-Environment Services Branch supports this project by providing this essential GIS (Geographic Information System) expertise. Riparian vegetation cover classified by the computer software is verified with on-site observations made from the intersections of the stream and roads. These are usually at bridges. One crossing has at least 4 points but some sites have up to 12 points or more. This depends on how varied the vegetation is. A point is entered and labeled on the digital image and a photo is taken on site for reference. Sometimes it can be tricky to decide if the vegetation is shrubs or trees. This method is efficient and it allows for a good vantage point, which helps in the classification. In 2011, 4 streams were verified totaling 310 km and 1250 vegetation points.
The following animation shows a portion of the Rat River in southeastern Manitoba, which was classified in 2009. The accuracy of the classification is estimated at over 90%. In this animation, the high-resolution aerial imagery is replaced by the vegetation classification layer. It is basically the digitization of the landscape features based on their shapes and colours as depicted by the imagery. It has been clipped by an arbitrary buffer width. This helps to keep file sizes and processing time manageable. Ideally, this would be clipped by the actual riparian zone. Digital elevation data can help to define the boundaries on the map.
How can we use this information?
Riparian program targeting
The classified riparian vegetation is provided to the partner CDs in the form of a GIS data layer. Additional tools that assist in the analyses of these data are also provided in the form of a “Riparian Toolbox”for the GIS. These are pre-programmed instructions for the GIS which automate the analysis and provide site-specific information that is related to the ecological health of the area. These include the calculation of:
- the amounts of land cover types within specified buffer widths - What is the relative combination of woody, herbaceous, and/or agricultural cover? These are often linked to riparian health.
- vegetation fragmentation - How continuous is the cover of trees and shrubs along the stream bank? If there are big gaps in woody vegetation, this may indicate impairment of the riparian zone.
- sinuosity – How bendy is the creek? Natural streams meander back and forth over the landscape. Man-made straightening of the waterway is called channelization. Water moves faster when the stream has been straightened, which means it has a higher potential for erosion and sediment transport. In general, streams with a high degree of channelization are at risk for impairment of riparian function.
It is important to not that these analyses provide a general indication of features that are known to be related to the health of the riparian zone. More in-depth investigations are required for a detailed riparian health assessment. This information supports the development and implementation of Integrated Watershed Management Plans, It will help CDs to prioritize and deliver riparian enhancement projects based on reliable information. For example, it helps to identify sites that may be at risk for impairment. It allows watershed managers to make the most effective use of limited program funds.
Supporting riparian and watershed awareness activities
Public education is an important part of this program. This new information will help to tailor workshops and awareness activities so that they are more meaningful and relevant to local residents. Riparian workshops provide practical information to watershed residents including local farmers, students, home and cottage owners, and other land managers. Contact your local CD office if you are interested in attending one of these workshops or for more information.
Agriculture and Agri-food Canada – Agri-Environment Services Branch generously provides GIS specialist services, other technical expertise and project guidance. Manitoba Conservation and Water Stewardship provides technical expertise and project guidance. The Manitoba Habitat Heritage Corporation and project partners also gratefully acknowledge the financial support provided by the RBC Blue Water Project™.