Hydrologic scaling for hydrogeomorphic floodplain mapping: Insights into human‐induced floodplain disconnectivity

Abstract

Hydrogeomorphic approaches for floodplain modelling are valuable tools for water resource and flood hazard management and mapping, especially as the global availability and accuracy of terrain data increases. Digital terrain models implicitly contain information about floodplain landscape morphology that was produced by hydrologic processes over long time periods, as well as recent anthropogenic modifications to floodplain features and processes. The increased availability of terrain data and distributed hydrologic datasets provide an opportunity to develop hydrogeomorphic floodplain delineation models that can quickly be applied at large spatial scales. This research investigates the performance of a hydrogeomorphic floodplain model in two large urbanized and gauged river basins in the United States, the Susquehanna and the Wabash basins. The models were calibrated by a hydrologic data scaling technique, implemented through regression analyses of USGS peak flow data to estimate floodplain flow levels across multiple spatial scales. Floodplain model performance was assessed through comparison with 100-year Federal Emergency Management Agency flood hazard maps. Results show that the hydrogeomorphic floodplain maps are generally consistent with standard flood maps, even when significantly and systematically varying scaling parameters within physically feasible ranges, with major differences that are likely due to infrastructure (levees, bridges, etc.) in highly urbanized areas and other locations where the geomorphic signature of fluvial processes has been altered. This study demonstrates the value of geomorphic information for large-scale floodplain mapping and the potential use of hydrogeomorphic models for evaluating human-made impacts to floodplain ecosystems and patterns of disconnectivity in urbanized catchments.

A comparison of four approaches to river landscape delineation: The case of small watercourses in the Czech Republic

“…The floodplain or river landscape definition on the basis of the digital elevation model has generally received a lot of attention (i.e., Noman et al, 2003;Charrier and Li, 2012;Deshpande, 2013), as it was a method based on relatively easily accessible data and, at the same time, sufficient accuracy of the outputs. Moreover, the increasing global availability of high-accuracy DEMs or DTMs (Digital Terrain Models) derived from earth observation technology (e.g., satellite, aerial or drones), offers new opportunities for advancing large-scale floodplain mapping (Nardi et al, 2018). Current and relatively accurate information on the area of great river floodplains can be obtained on the basis of elevation data processed by a fast geo-spatial tool for floodplain mapping (GFPLAIN 250m, see Nardi et al, 2019), but this tool is only suitable for large river systems.…”

Brief communication: Comparing top-down and bottom-up paradigms for global flood hazard mapping

“…In this paradigm, which can be seen as bottom-up, floodplains are identified directly from the topography (Nobre et al, 2011;Samela et al, 2017;Nardi et al, 2019), which is assumed to have been shaped by past flooding events, and building on the concept of fractal river basins (Bras and Rodriguez-Iturbe, 1985;Rodríguez-Iturbe and Rinaldo, 2001) or hydrogeomorphic theories (Bhowmik, 1984;Tarboton et al, 1988). The bottom-up paradigm does not require the estimation of a synthetic flood hydrograph, and consistently identify flood-prone areas across diverse climatic regimes with varying parametrizations (Manfreda et al, 2014;Nardi et al, 2018;Annis et al, 2019) which can be seen as an advantage in data-poor regions. Also, with the recent development of global DTMs (Ward et al, 2015;Nardi et al, 2019) and EO-based cloud computing platforms (Pekel, et al, 2016), worldwide mapping of floodplain areas is a reality and these global maps can be derived in a standard PC with a single click and limited computation time.…”

Integrating VGI and 2D hydraulic models into a data assimilation framework for real time flood forecasting and mapping

“…Boundary conditions were assigned considering both the flow measurements in the upstream part of the Tiber River and the flow hydrographs from 15 ungauged basins simulated by the adopted WFIUH hydrologic model. The computational domain was optimized adopting a hydrogeomorphic model (Nardi, Vivoni, and Grimaldi 2006;Nardi et al 2018b;Morrison et al 2018) according to Annis et al (2019) approach.…”