Over the past four decades, watershed assessments have evolved through a progression of three predominant scales: surface (“boots on the ground”), manned aircraft photography (various altitudes) and satellite imagery (over 400 miles altitude). However, with the advent of readily available, satellite imagery and computer software, high definition video and photography collected from aircraft has been under-utilized until now with the advent of relatively inexpensive unmanned aircraft systems (UAS, “drones”) equipped with nano-hyperspectral photography, thermal mapping and Laser Imaging Detection and Ranging (LiDAR) capabilities. We developed the Multi-Scale Watershed Assessment (MSWA) which offers a new and innovative approach to watershed and stream corridor assessment and modeling that is rapid, cost effective, reproducible and consistent.
The use of low altitude, high definition photogrammetry provides the following advantages: 1) Provides a rapid and reproducible method of covering more area expeditiously at the watershed and stream segment scales; 2) Acquiring private property access is generally not required; 3) Planform geometry (meander wave length, radius-of-curvature, and amplitude) is easily elucidated and measured using photogrammetry especially on large rivers; 4) Watershed-scale models can be tested, refined and finalized by re-visiting the video several times without additional field work; 5) Land use/cover and relative riparian zone condition is more obtainable; 6) Identification of sources of pollutants and sources of accelerated sediment is easily elucidated; 7) Identification of attainable reference conditions, by establishing the reference domain of all stream segments, is more easily achievable; 8) At the valley flat scale, video assessment facilitates the potential of re-coupling adjacent wetlands to the frequent flood event; 9) The upstream and downstream effects of dams (fish barriers) can be visualized better; 10) With future flyovers, trend analysis can be conducted at watershed and stream segment scales including monitoring natural and anthropogenic changes, catastrophic events, and effects of climate change on stream hydrology and geomorphology; (11) Linking watershed scale habitat variables to biological responses such as an Index of Biotic Integrity; and 12) Video assessment provides a platform such that the general public can visualize existing stream corridor conditions and envision future improvements.
The main thrust of MSWA is to provide a spatially explicit model designed for multi-scale applications at watershed and stream segment scales using low altitude photogrammetry (helicopter or UAS) (Figure 1). In regards to Technology Transfer and Transition, this service will transform labor intensive, on-ground data collection to rapid, inexpensive assessments using low altitude photogrammetry. Using statistical analysis, we developed and tested an ecological model (Stream Condition Index, SCI) for the Duck River Watershed, Tennessee:
Stream condition index (SCI) scores per HUC12 watersheds in the Duck River basin, TN
- used to prioritize watersheds for restoration, enhancement or conservation -
Where: CS = Channel Stability FC = Fish Cover P = Pools RZ = Riparian Zone BS = Bank Stability CAN = Canopy Density HA = Hydrologic Alteration WC = Water Color NE = Nutrient Enrichment EMB = Embeddedness CA = Cattle Access
Ecosystem restoration is one of the primary missions of the USACE Civil Works program (ER 1105-2-100, National Ecosystem Restoration, NER). This service is directly applicable to Sections 206, 1135, and 729 of the Water Resources Development Act of 1986, as revised (EC 1105-2-411). The approach is also pertinent to the compensatory mitigation requirements of the USACE Regulatory program (Clean Water Act, Section 404, NEPA). Watershed assessment at multi-scales using ecological modeling (SCI above) can be utilized to determine restoration outputs (Civil Works program) and ecological lift (Regulatory program) by forecasting future with and without project and calculating restoration credits for compensatory mitigation, respectively. In addition, this service will assist military installations in training/operations and construction activities where adverse effects to the environment may occur. The results can be used to avoid or minimize adverse impacts in regards to the National Environmental Protection Act (NEPA 1969) including Environmental Assessment (EIS) and the Clean Water Act (Section 404).
The Multi-Scale Watershed Assessment (MSWA) approach provides the following features/uses: • Determination of significant project prioritization and outputs for plan formulation and evaluation for aquatic ecosystem development (ER 1105-2-100). MSWA provides a competitive edge in awarded funding for Civil Works restoration projects. • The results of MSWA can be used for direct input into project justification (“J-sheets”). • Identification of disturbance regime and best attainable condition (Stoddard et al. 2006) applicable to reference standards and restoration targets (Figure 2). • Develop ecological models that can be used for trend analysis at multiple scales. • Address impacts and restoration actions beyond the restoration project footprint. • Prioritization of watersheds and stream segments for restoration, enhancement, and Stream condition index (SCI) scaled against environmental disturbance gradient (adapted from Pruitt et al. 2012).
Documentation and References
Pruitt, B.A., K.J. Killgore, W.T. Slack, L.E. Miranda, and C.A. Pruitt. In Review. Watershed Assessment: A multi-scale approach using ecological modeling. In proceedings of the 2017 Georgia Water Resources Conference, held April 19-20, 2017, University of Georgia, Athens, GA. Pruitt, B.A., S.J. Miller, C.H. Theiling, and J.C. Fischenich. 2012. The use of reference ecosystems as a basis for assessing restoration benefits. ERDC TN-EMRRP-EBA-11. Pruitt, B.A., K.J. Killgore, W.T. Slack, and L.E. Miranda. 2017. Model Documentation: Multi-Scale Watershed Approach, Duck River Watershed Assessment, Tennessee. In model review, ECO-PCX. Pruitt, B.A., K.J. Killgore, and W.T. Slack. 2017. Multi-Scale Watershed Assessment User Guide, Engineer Research and Development Center. In support of Duck River Watershed Plan, Final Watershed Assessment, U.S. Army Corps of Engineers, Nashville District. In model review, ECO-PCX. Stoddard, J., P. Larsen, C. P. Hawkins, R. Johnson, and R. Norris. 2006. Setting expectations for the ecological condition of running waters: The concept of reference conditions. Ecological Applications 16:1267-1276. USDA. 1998. Stream visual assessment protocol. United States Department of Agriculture, Natural Resources Conservation Service, National Water and Climate Center, Technical Note 99-1.