There are many approaches to mapping riparian areas with remote sensing methods. These methods–which vary significantly in difficulty, technical level, cost, accuracy, and objective–range from simple delineations of valley bottoms to detailed maps of riparian vegetation.
One of the most reliable and accurate methods for mapping riparian vegetation is image interpretation, by which an analyst manually maps riparian areas through visual interpretation of high-resolution stereo imagery. However, this can also be the most time consuming and expensive tactic. Alternatively, applying a buffer to a streamline is a fast, easy, and inexpensive to way define an area adjacent to a stream and most likely in a valley bottom, but also the least accurate.
The need for remote sensing methods that strike a reasonable balance between accuracy and expense has led to the development of a variety of approaches that combine different methods based on project needs. There is not one ideal approach; each project requires the selection of methods that are compatible with that project’s objectives and constraints. Most of the models rely upon discreet uplands and valley bottom landforms and are therefore best suited to terrains with steep to moderate relief. Their application to low relief landscapes should be done with caution, however, the integration of vegetation classification can enhance their applicability to these settings as well.
Two common remote sensing approaches to riparian mapping are mapping valley bottoms through geomorphic analysis, and delineating riparian areas through vegetation mapping. Frequently, these two approaches are combined. Mapping valley bottoms helps to identify the areas likely to be riparian, allowing vegetation mapping to focus in those areas. The Mapping Workflow, below, discusses this process, along with several special considerations.
The following links contain more information about valley bottom and vegetation mapping approaches, with additional links to short explanations of specific methods.
An important aspect of each mapping project is to identify potential riparian areas (i.e., riparian site potential). Potential riparian areas are those areas that, under normal conditions, would host riparian vegetation but have been impacted by a suite of factors, such as overgrazing and loss of shallow water table. Integrated valley bottom and vegetation mapping highlights those areas that could be riparian but lack riparian vegetation. Field investigations should be employed to evaluate those areas and to suggest changes in management practices.
Mapping Workflow
Riparian mapping efforts often involve mapping both valley bottoms and riparian vegetation. Successful mapping projects require careful planning and attention to a number of special considerations, and they typically follow a similar workflow. The list below outlines a common mapping workflow from initial planning to production of the final product. Within the list are links to pages that discuss special considerations for successful mapping.
- Establish project goals and the spatial extent of the study. See the Existing Vegetation Classification and Mapping Technical Guide.
- Determine the level of detail required to satisfy business needs.
- Determine constraints such as budget, imagery availability, and training data availability.
- Select and design the classification hierarchy consistent with the project’s needs and scale.
- Select imagery that has the required spectral resolution and strikes a balance between level of detail, spatial extent, and costs.
- Obtain training data appropriate for the method and imagery.
- Map valley bottoms and clip imagery to the area identified as potentially riparian.
- Map riparian vegetation within the valley bottoms.
- Assess the accuracy.
- Publish the final product.