OUTDATED Indicator V 2.0: Waterscapes: Resident Fish Connectivity

Resident Fish Connectivity
This layer was one of the old South Atlantic LCC indicators in the waterscapes ecosystem. It was an index of local barriers to fish and other aquatic species. Resident fish connectivity was not performing well as an indicator and could not be used in Blueprint 2.0. This indicator was replaced in Blueprint 2.1 with a new network complexity indicator.

Reason for Selection
Barriers to connectivity within rivers/streams can strongly impact aquatic diversity and alter natural movement of sediments, are easy to monitor and model, and are widely used and understood by diverse partners.

Input Data
Southeast Aquatic Connectivity Assessment Project: This project, a collaboration between The Nature Conservancy, the Southeast Aquatic Resources Partnership, and the South Atlantic LCC, identifies opportunities to improve aquatic connectivity by prioritizing dams based on their potential ecological benefit if removed or bypassed.

Waterbodies and Wetlands of the United States, 1:1,000,000 scale, from the National Atlas of the United states (2014). These data were used to identify major reservoirs and lakes.

National Land Cover Data (2011). These data were used to identify medium and high intensity urban areas.

Mapping Steps
Indicators intended for use in Blueprint 2.0 were initially computed, or in the case of existing data, were resampled to 1 ha spatial resolution using the nearest neighbor method. For computational reasons, we then used the Spatial Analyst aggregate function to rescale the resolution to 200 m. The aggregate function avoided loss of detail by taking the maximum value of each cell in the conversion (e.g., species presence).

SEACAP summarized the 4 metrics used in this index for dams within the South Atlantic LCC region:

Density of Small (Unsnapped) Dams in Upstream Functional Network Local Watershed (#/m⊃2;)
Density of Small (Unsnapped) Dams in Downstream Functional Network Local Watershed (#/m⊃2;)
Density of Road & RR / Small Stream Crossings in Upstream Functional Network Local Watershed (#/m⊃2;)
Density of Road & RR / Small Stream Crossings in Downstream Functional Network Local Watershed (#/m⊃2;)

These 4 metrics were used in SEACAP to measure how altered the connectivity is around each dam in the consensus prioritization for resident fish. The consensus prioritization was selected by a team of aquatic experts and is used as the default way to identify which dams should be highest priority for improving connectivity. The other metrics in that prioritization (e.g., impervious surface) are already captured by other South Atlantic LCC indicators. In the concensus prioritization, SEACAP weighted the importance of stream crossings twice as high and small dams. To maintain consistency with that approach. We created a weighted index from the 4 metrics:

Index = Small dam density upstream * 0.175 + Small dam density downstream * 0.175 + Stream crossings density upstream * 0.325 + Stream crossing density downstream *0.325

We summed this Index value for each dam across all dams in the HUC12 subwatershed resulting in a single value for each HUC12. By summing the index value we account for the accumulated impacts of multiple dams within a watershed. However, since the value is summed across all the dams (and not averaged), it does not translate directly to the average density of barriers.

We then grouped the index into 5 categories (No dams or crossings, <0.1, 0.1 - 1, 1-5, >5) and assigned indicator values to each category (4, 3, 2, 1, 0), with 4 being areas of highest quality for this indicator (No dams or crossing) and 0 being areas of lowest quality for this indicator.

After reviewing these results, it became apparent that there were many subwatersheds that did not have dams in them (thus receiving the highest score) but still had substantially altered connectivity for resident fish. These watersheds fell into 2 categories: 1) heavily urbanized areas with no dams where much of the stream network was underground and 2) areas where reservoirs altered connectivity but there were no dams in the local subwatershed. To deal with these two issues, we scored all subwatersheds that had no dams but > 10% medium and high density urban and/or a lake or reservoir as a 2.

Indicator Value vs. Index
Indicator values were assigned as follows:

4 : 0 (only if there is <10% medium and high density urban and/or a lake or reservoir in the HUC12)
3 : <0.1
2 : 0.1 - 1 (or if there is >10% medium and high density urban and/or a lake or reservoir in the HUC12)
1 : 1 - 5
0 : >5

Indicator Overview
The South Atlantic ecosystem indicators serve as the South Atlantic LCC's metrics of success and drive the identification of priority areas for shared action in the Conservation Blueprint. To learn more about the indicators and how they are being used, please visit the indicator page. Check out the Blueprint page for more information on the development of the Blueprint, a living spatial plan to conserve our natural and cultural resources.

Literature Cited
Martin, E. H, Hoenke, K., Granstaff, E., Barnett, A., Kauffman, J., Robinson, S. and Apse, C.D. 2014. SEACAP: Southeast Aquatic Connectivity Assessment Project: Assessing the ecological impact of dams on Southeastern rivers. The Nature Conservancy, Eastern Division Conservation Science , Southeast Aquatic Resources Partnership. < maps.tnc.org/seacap>

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OUTDATED Indicator V 2.0: Waterscapes: Resident Fish Connectivity

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