RIVER RESPONSE TO ENVIRONMENTAL CHANGE: LEVERAGING EARTH’S SELF-RECORDED SEDIMENTARY AND BIOGEOCHEMICAL ARCHIVES TO CALIBRATE HYDROLOGIC AND GEOMORPHIC MODELS

Long-term trends in Earth’s climate system often condition landscape evolution on human timescales. As human influence on Earth’s climate and landscapes grows, the survival of many will be contingent upon our ability to forecast and adapt to the rapid environmental changes that result. Rivers and their floodplains, home to a large fraction of the human population, are at the forefront of accelerated change; as the earth warms and precipitation patterns alter, so do catchment ecosystems and the frequencies and magnitudes of river floods. Computational geomorphic models are valuable tools for forecasting water and sediment dynamics through river corridors; however, these models are rarely built to characterize river evolution over the centennial or millennial time-scales relevant to the lifetimes of multiple generations. While river gages record high-resolution data-series of flow characteristics that are used to inform hydraulic and geomorphic models, the record-lengths are usually limited to recent decades when river catchments, floodplains and channels were already fundamentally modified by humans. Earth’s deep-time sedimentary and biogeochemical archive represents the only pristine dataset against which modeled forecasts of climate, ecosystem and river dynamics can be calibrated. However, quantitative reconstructions of hydrodynamics, channel hydraulic geometry and sediment transport dynamics from ancient river landscapes and estimates of past climatic variability are rarely leveraged in concert to comprehensively characterize environmental change at Earth’s surface.

Here, we present an overview of ongoing efforts to bridge the disconnect between tools that have historically been used in isolation and applied on disparate timescales, i.e., human/engineering timescales versus deep time, to characterize climate, ecosystem and river dynamics. We summarize workflows, successes and challenges associated with developing (a) long timescale river models calibrated against (b) paleohydraulic and sediment transport reconstructions from deep time fluvial sedimentary records and (c) reconstructions of terrestrial paleoclimate.