As runoff patterns shift with a changing climate, it is critical to effectively communicate current and future flood risks, yet existing flood hazard maps are insufficient. Modifying, extending, or updating flood inundation extents is difficult, especially over large scales, because traditional floodplain mapping approaches are data and resource intensive. Low-complexity floodplain mapping techniques are promising alternatives, but their simplistic representation of process falls short of capturing inundation patterns in all situations or settings. To address these needs and deficiencies, we formalize and extend the functionality of the Height Above Nearest Drainage (i.e., HAND) floodplain mapping approach into the probHAND model by incorporating an uncertainty analysis. With publicly available datasets, the probHAND model can produce probabilistic floodplain maps for large areas relatively rapidly. We describe the modeling approach and then provide an example application in the Lake Champlain Basin, Vermont, USA. Uncertainties translate to on-the-ground changes to inundated areas, or floodplain widths, in the study area by an average of 40%. We found that the spatial extent of probable inundation captured the distribution of observed and modeled flood extents well, suggesting that low-complexity models may be sufficient for representing inundation extents in support of flood risk and conservation mapping applications, especially when uncertainties in parameter inputs and process simplifications are accounted for. To improve the accuracy of flood hazard datasets, we recommend investing limited resources in accurate topographic datasets and improved flood frequency analyses. Such investments will have the greatest impact on decreasing model output variability, therefore increasing the certainty of flood inundation extents.

The study described in this report was motivated by a need to provide a baseline understanding of the functioning of floodplains in the Lake Champlain Basin. Because floodplains can store and transform sediment and nutrients derived from the upstream watershed, many stakeholders in the Lake Champlain Basin are interested in restoring, protecting, or enhancing these natural features to optimize their role in water quality improvements. There is a lack of data, however, on the distribution of floodplains and the rate at which river-derived sediment and associated nutrients are deposited.

In this project, we collected and analyzed data that describe the status and function of floodplains along Lake Champlain Basin rivers to assist in watershed planning for improved water quality. First, we created an inventory of floodplains and identified their degree of hydrologic connectivity, through the development of a low-complexity floodplain mapping model. Flood-derived sediment and phosphorus deposition rates collected from a floodplain monitoring network provided a measure of the capacity of floodplains to capture sediment and phosphorus. Statistical models were developed to describe the functional relationship between deposition rates and the physical attributes of the upstream watershed, and more locally along the river channel and floodplain. We then used these statistical models to establish a framework for evaluating where to prioritize floodplain management efforts and the efficacy of such investments in meeting load reduction targets. Our efforts focused on those streams in Vermont whose upstream drainage area was 10 mi2 or greater, and on a range of watershed settings where it was likely that floodplains can act as sediment sinks. The resulting management framework may be applied throughout the Basin, given the availability of high resolution geo-spatial datasets.

In recent years there has been increasing concern nationwide about the amount of unregulated organic pollutants entering surface waters from storm drains, wastewater treatment facilities (WWTFs), and agricultural activities. The presence, environmental fate, and effects of these Organic Contaminants of Emerging Concern (OCECs), have started to receive widespread attention in the Great Lakes, the Chesapeake Basin and elsewhere across the country. In the Lake Champlain Basin of Vermont, New York, and Québec, there have been several investigations of OCECs in the last 20-30 years. This report seeks to bring all of this information together in one place as a starting point for determining gaps in our knowledge as well as future research and management needs. The emphasis is on reporting the presence, extent, and sources of anthropogenic organic contaminants present in the water column of the Lake Champlain Basin. Summarizing effects on the people and biota of the Champlain Basin is beyond the scope of this work. Whenever possible, raw data is included in this report so that the reader can see exactly what data exists, what is missing, and draw their own conclusions about future needs.

Data is presented on pesticides, industrial wastewater contaminants, hormones, pharmaceuticals, and personal care products found in surface water, drinking water, Wastewater Treatment Facility inputs and effluents. Data has been supplied by state, provincial, university and federal researchers for research projects both recently completed and still on-going.

The 2020 Report of Activities highlights LCBP projects that were in progress or concluded between October 1, 2019 and September 30, 2020. It includes a comprehensive listing of external contracts managed by LCBP, and key LCBP tasks implemented by staff during this time period. The LCBP received federal funding in FY 2020 from the U.S. Environmental Protection Agency, the Great Lakes Fishery Commission, and the National Park Service.

The 2020 Summary Report of Activities highlights LCBP projects that were in progress or concluded between October 1, 2019 and September 30, 2020. It includes a comprehensive listing of external contracts managed by LCBP, and key LCBP tasks implemented by staff during this time period. The LCBP received federal funding in FY 2020 from the U.S. Environmental Protection Agency, the Great Lakes Fishery Commission, and the National Park Service.

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