We have developed a protocol for the assessment of stream crossings, including data forms, instructions, and training materials, all available on our NAACC Documents page. A web-based database was then created to serve as a convenient repository for the data collected during crossings surveys.
Anyone can survey crossings using NAACC protocols but they must belong to an organized regional group headed by a designated survey coordinator. Training and certification are also required, to ensure high quality data.
Assessment Protocol
Trained Lead Observers certified to assess crossings use a uniform protocol throughout the thirteen state, North Atlantic region.
This protocol includes observations of the crossing (for example road type, flow condition, crossing alignment) and of the structure itself (for example material, shape, dimensions).
The Instruction Manual for Aquatic Passability Assessments in Non-tidal Streams and Rivers explains this survey protocol for use with either paper field data forms or an electronic version of the forms - the offline data manager (ODM) - that can be used with smart phones, tablets and laptop computers. The field data form and instruction manual for this protocol are available under NAACC Documents.
Scoring for Passability
The NAACC has finalized two scoring systems to help interpret data collected from stream crossing assessments:
- A classification scoring approach, where each crossing is assigned to one of three categories based on the degree of aquatic organism passage (AOP) through the structure: full AOP, reduced AOP, and no AOP.
- A numerical scoring approach, where mathematical formulas using the data from the assessment are used to compute a numeric score for each crossings. Scores range from 0 (no aquatic passability) to 1 (full aquatic organism passage).
Upon entry into the database, all crossings are automatically scored by both scoring systems. In the mapping interface we currently show only the numeric passability score and associated descriptors. We are planning to implement changes in the map viewer that will allow users to choose whether to display the numeric score descriptors or the AOP classification
Aquatic Connectivity Scoring Systems for Non-tidal Crossings
Prioritization
The NAACC has completed a HUC12 subwatershed prioritization to help identify subwatersheds that may be higher priority for field survey.
The prioritization included criteria such as diadromous fish, brook trout, likelihood of crossing failure, greater uncertainty of crossing passability, and impact of crossing failure.
The results of the prioritization, which may be viewed for the entire NAACC region or stratified by state, are displayed on a web map and can be explored through use of a customizable tool for use with ArcGIS Desktop.
You can learn how to use the web map and custom tool in our Prioritization for Field Inventory webinar:
Please contact Erik Martin with any questions about this prioritization.