Floodplain Inundation Research Articles

The implications of brief floodplain inundation for local and landscape-scale ecosystem function in an intermittent Australian river

The implications of brief floodplain inundation for local and landscape-scale ecosystem function in an intermittent Australian river

Physical-statistical model for forecasting maximum snowmelt-induced stages (the Ob river near the city of Barnaul as a case study)

For the regions with a long-term snow cover, the amount of solid precipitation is one of the driving factors in the formation of floods. The article considers the possibility of using the orographic correction to the velocity of vertical movements of air masses due to the relief in estimating winter precipitation and forecasting maximum snowmelt-induced stages. The significant influence of autumn freezing on the floodplain inundation and, accordingly, maximum water levels of the Ob River near the city of Barnaul is shown.

Sequential Changes in Coastal Plain Rivers Influenced by Rising Sea-Level

Coastal backwater effects on low-gradient coastal plain rivers extend well upstream of the head of the estuary and propagate upstream as sea-level rises. Hydrological, geomorphological, and ecological indicators can serve as sentinels of the upriver encroachment. Analyzing the along-river spatial distribution of these indicators as a space-for-time substitution allows the prediction of sequential changes. Interpretation of results from 20 rivers in Virginia and the Carolinas shows that backwater effects at the leading edge result in higher river stages, increasing floodplain inundation, and raising water tables. Lower slopes and flow velocities reduce sediment transport, reducing river sediment input and floodplain deposition. This inhibits natural levee development, reducing bank heights. These factors combine to increase the frequency and duration of inundation, resulting in semi-permanently flooded wetlands. Anaerobic conditions limit organic decomposition, and ponding allows transported and suspended organic matter to settle, leading to organic muck and peat floodplain soils. This accumulation, coupled with general valley-filling, buries alluvial terrace remnants. Finally, vegetation changes driven by salinity increases occur, resulting in swamp conversions to brackish marsh. Backwater encroachment is strongly controlled by channel bed slope, with relatively steeper channels experiencing slower rates of tidal extension. With accelerating sea-level rise (SLR), the lowest-sloping channels could experience encroachment rates of >1 km yr−1. Hydrological changes associated with SLR are most rapid at the leading, upriver end—averaging 71 km upstream of the head of the estuary in the study rivers at present—and at the lowermost, downstream end of the fluvial-estuarine transition zone.

An evaluation of tradeoffs in restoring ephemeral vs. perennial habitats to conserve animal populations

IntroductionHabitat loss and degradation pose significant threats to global fish and wildlife populations, prompting substantial investments in habitat creation and restoration efforts. Not all habitats provide equal benefits, leading to challenges in prioritizing restoration actions. For example, juvenile anadromous salmonids require high quality rearing aquatic habitats to achieve the physiological requirements needed to successfully migrate to the ocean. However, there are profound disagreements among anadromous salmon restoration managers whether it is best to focus efforts on restoring in-channel habitats that are available for the entire rearing period or floodplain habitats that, while facilitating greater growth and survival than in-channel habitats, are only available for a few weeks at a time and are typically only activated every two-to-three years.MethodsWe used an existing fall-run Chinook salmon decision-support model to evaluate under what conditions floodplain restoration would provide greater benefits than in-channel habitat restoration. The simulations included a wide range of floodplain inundation frequencies and durations and floodplain benefits in the form of increased survival and growth relative to in-channel habitats.ResultsThe simulations results indicated that in-channel habitat restoration was always the best habitat restoration action when there was no existing in-channel habitat despite simulating a wide range of flood frequency, duration, and growth and survival benefits. Floodplain restoration was generally best when there was sufficient in-channel habitat available to successfully rear most of the juveniles produced by the returning adult salmon.DiscussionWe hypothesize that in-channel and floodplain habitats have different roles in salmon population maintenance with in-channel habitats regulating the overall population size and floodplains acting as recurrent resource pulses. Our study provides a quantitative framework to evaluate the benefit of these two habitat types and provides generalizable rulesets that can be used by managers when implementing habitat restoration strategies for species that inhabit both in-channel and floodplain habitats.

Seeing the floods through the trees: Using adaptive shortwave infrared thresholds to map inundation under wooded wetlands

AbstractAccurate information about the extent, frequency and duration of forest inundation is required to inform ecological, biophysical and hydrological models and enables floodplain managers to quantify the efficacy of flood mitigation/modification activities. Open water classifiers derived from optical remote sensing typically underestimate or fail to detect floodplain forest inundation. This paper presents a new method for detecting forest inundation dynamics using freely available Landsat and Sentinel 2 data, referred to as short‐wave infrared mapping under vegetation. The method uses a dynamic threshold that accounts for the additional shortwave infrared reflectance caused by the presence of tree canopies over floodwater. The method is demonstrated at five Ramsar listed River Red Gum floodplain forest wetlands in southeastern Australia. Accuracy assessment based on independent drone imagery from a wide range of vegetated wetlands showed an absolute accuracy of 67%–70% and a fuzzy accuracy of 81%–83%. We found the method is conservative, and underestimates inundation (16%–18%) but very rarely misclassifies dry pixels as inundated (0.3%–0.6%). When compared to river gauge data, the method shows similar trends to an open water classifier (i.e., the area of inundated vegetation increases with increasing river height). The method is conservative compared to lidar‐based floodplain inundation models but can be applied wherever cloud‐free scenes of Landsat or Sentinel 2 have been acquired, thereby enabling floodplain managers with the ability to quantify changes in inundation dynamics in places/time‐periods where lidar is unavailable.

Critical linkages among floodplain hydrology, geomorphology and ecology along a lowland meandering river, Illinois, USA

AbstractThe ecology of forested floodplains is intricately linked to river hydrology through the frequency, magnitude, timing and duration of floodplain inundation. Spatial variability in inundation characteristics is influenced by the geomorphic template of a floodplain, both in terms of the topography of floodplain features and connectivity of these features to the main river channel. Spatial variability in inundation, in turn, has the potential to produce spatial variability in forest ecological characteristics. This study examines the influence of floodplain geomorphic features on spatial variability in inundation frequency as well as the relationship between these geomorphic features and the ecological characteristics of a floodplain forest. The frequencies of floods of different magnitudes are determined from flow‐duration analysis of over 100 years of discharge data for a lowland meandering river in Illinois, USA. Data on discharge, stage, and topography are then used to calibrate a two‐dimensional hydraulic model of flow across the floodplain at different levels of inundation. Integrating the frequency and inundation data yields mapping of average annual inundation frequency for different parts of the floodplain. Significant differences in inundation frequency correspond to three distinct floodplain geomorphic features: secondary channels (frequency = 12%), closed depressions (frequency = 4%) and the floodplain surface (frequency = 3%). Tree density is similar among the three types of geomorphic features, but tree species composition and canopy density differ significantly between secondary channels and the floodplain surface. The results provide insight into linkages among hydrology, geomorphology and tree characteristics of forested floodplains of lowland meandering rivers.

Trade-offs between nitrogen and phosphorus removal with floodplain remediation in agricultural streams

To improve water quality and reduce instream erosion, floodplain remediation along agricultural streams can provide multiple ecosystem services through biogeochemical and fluvial processes. During floodplain inundation, longer water residence time and periodic anoxic conditions can lead to increased nitrogen (N) removal through denitrification but also mobilization of phosphorus (P), impeding overall water quality improvements. To investigate the capacity for N and P processing in remediated streams, we measured potential denitrification and nitrous oxide production and yields together with potential P desorption and P fractions in floodplain and stream sediments in ten catchments in Sweden. Sediment P desorption was measured as equilibrium P concentration, using P isotherm incubations. Denitrification rates were measured with the acetylene inhibition method. Sediment nutrient process rates were combined with hydrochemical monitoring along remediated streams and their paired upstream control reaches of trapezoidal shape to determine the impact of floodplains on water quality. The correlation between floodplain denitrification rates and P desorption (r = 0.53, p = 0.02) revealed a trade-off between soluble reactive P (SRP) and nitrate removal, driven by stream water connectivity to floodplains. Nitrous oxide production was not affected by differences in P processing, but nitrous oxide yields decreased with higher denitrification and P desorption. The release of SRP from floodplains (0.03 ± 0.41 mg P kg−1 day−1) was significantly lower than from trapezoidal stream banks (0.38 ± 0.37 mg P kg−1 day−1), predicted by long-term SRP concentrations in stream water and floodplain inundation frequency. The overall impact of SRP release from floodplains on stream SRP concentrations in remediated reaches was limited. However, the remediated reaches showing increased stream SRP concentrations were also frequently inundated and had higher labile P content and coarse soil texture in floodplain sediments. To fully realize the potential for water quality improvements with constructed floodplains in agricultural streams, the promotion of denitrification through increased inundation should be balanced against the risk of P release from sediments, particularly in streams with high SRP inputs.

High-resolution impact-based early warning system for riverine flooding

Despite considerable advances in flood forecasting during recent decades, state-of-the-art, operational flood early warning systems (FEWS) need to be equipped with near-real-time inundation and impact forecasts and their associated uncertainties. High-resolution, impact-based flood forecasts provide insightful information for better-informed decisions and tailored emergency actions. Valuable information can now be provided to local authorities for risk-based decision-making by utilising high-resolution lead-time maps and potential impacts to buildings and infrastructures. Here, we demonstrate a comprehensive floodplain inundation hindcast of the 2021 European Summer Flood illustrating these possibilities for better disaster preparedness, offering a 17-hour lead time for informed and advisable actions.

Quantifying intra‐ and inter‐annual dynamics of river‐floodplain connectivity and wetland inundation with remote sensing and wavelet analysis

AbstractWe used imagery from remote sensing (FORCE Time Series Analysis submodule (combining Landsat and Sentinel‐2 imagery) to derive spatially distributed times series (8 years) of NDWI data to infer patterns of floodplain inundation and river‐floodplain connectivity in two contrasting polders in the Lower Oder Valley National Park. The upstream Polder A (14.4 km2) was extensively flooded for prolonged periods most winters. Wavelet analysis showed that this strong seasonality was primarily driven by winter water levels in the river Oder that could enter and leave the polder through two opened floodgates. Subsequent drainage was slow and aided by a pumping station. Inundation of the downstream Polder 10 (17.7km2) was lower and had less marked seasonality. This reflected the impact of flood attenuation by storage in Polder A upstream, but also the greater connectivity (via 10 floodgates) to the Oder and a functional network of channels, which facilitated rapid drainage after flood peaks. In Polder A, secondary periods of transient inundation could also occur in response to local intense summer rainfall. Wavelet analysis also showed that groundwater recharge in and around Polder A is primarily induced by floodwater, whilst Polder 10 also reflects the influence of local rainfall‐driven recharge. The flood regimes of the two polders showed marked inter‐annual variation, largely dependent on flows from the upper Oder catchment. Understanding these patterns and processes of inundation is important for both managing flows and sustaining valuable wetland habitats within the National Park. Given projected climate change in eastern Europe and possible management alterations to the flow regime of the Oder, the potential implications for these habitats needs urgent attention.

Restoring freshwater habitat mosaics to promote resilience of vulnerable salmon populations

AbstractPhenotypic diversity and abundance drive salmon resilience in the face of increasing environmental variability. But what happens when human activities fundamentally alter the habitat complexity that drives this diversity? And how can we restore habitats to recover both diversity and abundance to support salmon persistence in a warming climate? Here, we looked at the impact of a large watershed restoration effort on the abundance and climate resilience of the three remaining core natural spring‐run Chinook Salmon populations in the California Central Valley (Butte, Mill, and Deer Creek). Butte Creek fish, which have floodplain access, had higher overall productivity and faster juvenile growth compared with Mill and Deer Creek populations, and the proportion of floodplain inundation was positively correlated with Butte Creek adult abundance two years later. While Butte Creek exhibited significant increases in abundance post‐restoration (~2000%), it generally exhibited lower phenotypic diversity and only a marginal increase in population stability after restoration based on the coefficient of variation (CV). In particular, Butte Creek salmon tended to exhibit larger drops in escapement following dry years (e.g., return years 2010, 2017) compared with Mill and Deer Creek populations, presumably due to limited inundation of its downstream floodplain. The late‐migrating juvenile strategy (i.e., yearling), which disproportionately supported Mill and Deer Creek populations during droughts, was uncommon among Butte Creek adults (averaging 60% of returns for Mill and Deer Creek vs. 0.3% for Butte Creek). Increased spring‐run stock complex stability was found, post‐restoration, when combining the three spring‐run populations (i.e., lower aggregate CV). However, among‐river pairwise correlations also suggested increased synchronization in population abundances post‐restoration, potentially due to increasing frequency and severity of extreme climatic events (e.g., droughts and ocean warming). This study underscores the importance of restoring a connected mosaic of aquatic habitats across modified landscapes, such as cold water refugia and floodplains, to preserve multiple (across‐population) life history pathways for increasing salmon stock complex stability and abundance. These landscape‐scale process‐based habitat restoration efforts are likely to be crucial for the successful long‐term recovery of vulnerable species in a rapidly changing climate.

Escaping the dry: Native and non‐native fish outmigration from a receding floodplain following managed inundation

Abstract Many fish rely on being able to move between rivers and floodplains to fulfil key life history events, but river regulation has reduced floodplain inundation compromising these connections and causing the loss of ecosystem function more generally. Managed inundations are being trialled in some systems as a solution, whereby engineered floods using built infrastructure, such as floodplain regulators, are used to deliver water to inundate floodplains. However, the use of managed inundations is still in early stages and their outcomes for native fish have been rarely assessed. We present the results from a series of investigations assessing the effectiveness of two managed inundations on the native fish community in a large floodplain in south‐eastern Australia. We firstly described changes in fish assemblages in wetlands before and after managed inundation (Aim 1). We then examined which potential exits are used by golden perch, a highly mobile species that regularly moves between rivers and floodplains (Aim 2), and then assessed outmigration patterns of native and non‐native species during receding phase from one of the major golden perch exits via a fishlock (Aim 3). Finally, we conducted two experiments to test if it was possible to modify operation of the fishlock to maximise fish movement by varying the length of the operating cycle, or whether operation occurs during the day or night (Aim 4). We found that native fish dominated the catch in wetlands before drawdown of the managed inundation, but that non‐native species, especially young‐of‐year carp, dominated after the drawdown (Aim 1). Outmigrating golden perch left the floodplain wetlands in a variety of locations but predominantly through a fishlock, which is a type of fishway (Aim 2). At this fishlock, native fish outmigrated before and during the early phase of the floodplain recession, moving to permanent riverine habitats, whereas non‐native fish (mostly carp) tended to migrate later in the recession especially as water levels dropped (Aim 3). There were no substantive differences in the numbers and size of fish moving through the fishlock at different operating cycle times (Aim 4). While there were no differences in numbers of non‐native carp migrating during the day or night, native species (carp gudgeon and Australian smelt) were more common during the day. Our study has provided knowledge of the eco‐hydraulic mechanisms of fish movement, in relation to managed inundaitons. This knowledge can be applied to help water managers plan floodplain watering regimes in the Murray‐Darling Basin to benefit native fish, while potentially restricting movement of undesirable non‐native species such as carp. More broadly, our results improve current understanding of fish movement in relation to managed floodplain recession, which is critical given the increased use of such managed inundations, and the need for information to help design and evaluate them.

Towards an Indian land data assimilation system (ILDAS): A coupled hydrologic-hydraulic system for water balance assessments

Effective management of water resources requires reliable estimates of land surface states and fluxes, including water balance components. But most land surface models run in uncoupled mode and do not produce river discharge at catchment scales to be useful for water resources management applications. Such integrated systems are also rare over India where hydrometeorological extremes have wreaked havoc on the economy and people. So, an Indian Land Data Assimilation System (ILDAS) with a coupled land surface and a hydrodynamic model has been developed and driven by multiple meteorological forcings (0.1°, daily) to estimate land surface states, channel discharge, and floodplain inundation. ILDAS benefits from an integrated framework as well as the largest suite of observation records collected over India and has been used to produce a reanalysis product for 1981–2021 using four forcing datasets, namely, Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2), Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), ECMWF’s ERA-5, and Indian Meteorological Department (IMD) gridded precipitation. We assessed the uncertainty and bias in these precipitation datasets and validated all major components of the terrestrial water balance, i.e., surface runoff, soil moisture, terrestrial water storage anomalies, evapotranspiration, and streamflow, against a combination of satellite and in situ observation datasets. Our assessment shows that ILDAS can represent the hydrological processes reasonably well over the Indian landmass with IMD precipitation showing the best relative performance. Evaluation against ESA-CCI soil moisture shows that MERRA-2 based estimates outperform the others, whereas ERA-5 performs best in simulating evapotranspiration when evaluated against MODIS ET. Evaluations against observed records show that CHIRPS-based estimates have the highest performance in reconstructing surface runoff and streamflow. Once operational, this system will be useful for supporting transboundary water management decision making in the region.

Damming consequences: Quantifying the effects on channel geometry and floodplain inundation

Dams have a profound effect on floodplain inundation and channel geometry. Still, few studies have analyzed detailed channel geometry changes, especially as they affect downstream floodplain inundation on large rivers. This research compared the Apalachicola River depths and floodplain inundation downstream of the Jim Woodruff Dam between early and late post-dam periods. We used hydrographic data for 1960 and 2010 collected by the U.S. Army Corps of Engineers. A ≤1.2 point/m2 LiDAR point cloud covering the entire floodplain was fused with the hydrographic data. After a forward and inverse transformation between coordinate systems, the combined data was converted into a riverbed digital elevation model (DEM). River geometric properties were calculated (Area, channel width, mean depth, thalweg elevation, and width-to-mean-depth ratio) for 1960 and 2010. Daily discharge and stage data (1928–2020) were collected for Chattahoochee and Blountstown gauge stations. Eleven flows, between the 10th and 99th percentile extracted from the daily flow duration curve for early and late post-dam periods, were used in a 2D hydrodynamic model, Hydrologic Engineering Center's River Analysis System (HEC-RAS) to simulate floodplain inundation. The result reveals that the riverbed degraded by about 1.5 m near the dam. Geometric changes between early and late post-dam periods include upper reaches deepening and narrowing (mean depth changed from ∼6.0 to ∼7.3 m with a consistent width), while the lower reach exhibited shallowing and widening (mean depth went from ∼6.0 m to ∼5.0 m). The channel area generally increased between the periods. Inundation depth was reduced by ∼1.0 m, for most flow categories, and decreased by 15 % from 1960 to 2010 for similar flows between the periods, particularly for the upper and middle reaches. Floodplain inundation extent deacreased by about 24.1 % for flow of ∼513 m3/s. The inundation decreases was partly due to alteration in geometric properties. This study highlights the need for comprehensive river morphology assessments to address human-induced degradation, changing inundation patterns, and their global implications in similar riverine ecosystems.

Using hydraulics to evaluate ecological benefits, risks, and trade‐offs from engineered flooding

AbstractRegulation and water extraction have reduced river flow worldwide. In some rivers, this has led to reductions in the frequency and duration of floodplain inundation and, in turn, declining condition of flood‐dependent vegetation. One management response has been the construction and modification of infrastructure, or ‘regulators’, to engineer floodplain inundation at discharges that do not otherwise cause overbank flooding. Such actions have the potential to benefit floodplain vegetation, yet the atypical hydrodynamics of engineered floods may threaten riverine ecological processes and biota and increase the risk of adverse water quality. We investigated the influence of engineered flooding, and associated reductions to in‐channel hydraulics, on key ecological processes. Specifically, the transport and retention of larvae of an iconic fish species (Murray Cod, Maccullochella peelii), and a common microinvertebrate Trichocerca. Analysis of different flow management scenarios for floodplain inundation indicates that maintaining in‐channel velocities greater than 0.2 m s−1 produces higher Trichocerca densities, while velocities greater than 0.3 m s−1 creates suitable habitat for Murray cod larvae, thereby providing targets for avoiding detrimental effects of engineered floods on in‐channel biota. To evaluate responses to regulator operation, velocity was represented by a hydrological model using pre‐computed results from detailed hydrodynamic models. These results were used to relate upstream discharge and downstream water level to the proportion of each reach in the hydrological model meeting each velocity criterion. The model also represents changes in discharge, inundated area and a water quality parameter, dissolved oxygen. Model scenarios for engineered floodplain inundation were used to demonstrate the potential benefits, impacts and trade‐offs between the different metrics identified. The model framework enables a more holistic evaluation of infrastructure operation, extending analysis beyond discharge and inundated area to risks and benefits to key indicators of the ecosystem. This refined integrated approach to the management of regulated river systems may become critical in the future where water resources are projected to further decline under a changing climate.

Google Earth Engine‐Based Estimation of the Spatio‐Temporal Distribution of Suspended Sediment Concentrations in a Multi‐Channel River System of the Yangtze River Basin

AbstractLowland multi‐channel alluvial river systems are highly variable in frequency and magnitude of floodplain inundation and are vulnerable to human activities such as damming. In the Yangtze River Basin, the Three Gorges Dam (TGD) has trapped >80% of upstream sediment supply, causing downstream scouring and rapid geomorphic changes in river and its floodplain lakes. Suspended sediment concentration (SSC) is widely used to monitor river morphodynamics, but traditional measurements of SSC are time consuming, costly and difficult to quantify SSC in a large spatial scale. Using Google Earth Engine and in situ observed hydrological data, we created a multiple linear regression model to map SSC in the multi‐channel system Songzi River of the Yangtze. The new SSC predictive model achieved high accuracy (R2: 0.87) and showed opposite downstream trends in SSC during peak flood years and normal flood years. For the first time, we found that in the peak flood year of 1998 the study rivers exhibit a downstream increase trend of SSC with an abrupt increase in their middle reach, while SSC in normal flood years experiences a downstream decline with minimal changes. A prominent difference in SSC is also revealed after the TGD with a reduction of 60%. Furthermore, SSC in the closely hydrologically connected lakes is more dynamic than the less connected lakes. Our study demonstrates that the proposed method enables to rapidly quantify the spatio‐temporal SSC distribution in the multi‐channel systems on the floodplain of large alluvial rivers and highlights the importance of connectivity in regulating SSC dynamics.

Brief floodplain inundation provides growth and survival benefits to a young-of-year fish in an intermittent river threatened by water development

Riverine floodplains are highly productive habitats that often act as nurseries for fish but are threatened by flow regulation. The Fitzroy River in northern Australia is facing development, but uncertainty exists regarding the extent to which floodplain habitats deliver benefits to fish, particularly given the brevity of seasonal floodplain inundation. We investigated the growth rate of young-of-year bony bream (Nematalosa erebi) in main channel and ephemeral floodplain habitats using age derived from otolith daily increments. We also investigated potential mechanisms influencing growth and modelled the consequences of differential growth rate on survival. Our results revealed higher growth occurred exclusively on the floodplain and that zooplankton biomass was the best predictor of growth rate. Modelling indicated that elevated growth rate in high-growth floodplain pools (top 25th percentile) could translate into substantial increases in survivorship. The positive effect of zooplankton biomass on growth was moderated under highly turbid conditions. Temperature had a minor influence on growth, and only in floodplain habitats. Our results indicate ephemeral floodplain habitats can deliver substantial growth and survival benefits to young-of-year fish even when floodplain inundation is brief. This study highlights the need to ensure that water policy safeguards floodplain habitats due to their important ecological role.

The floodplain inundation history of the Murray-Darling Basin through two-monthly maximum water depth maps

With growing concerns over water management in rivers worldwide, researchers are seeking innovative solutions to monitor and understand changing flood patterns. In a noteworthy advancement, stakeholders interested in the changing flood patterns of the Murray Darling Basin (MDB) in Australia, covering an area of 1 million km2, can now access a consistent timeseries of water depth maps for the entire basin. The dataset covers the period from 1988 to 2022 at two-monthly timestep and was developed using remotely sensed imagery and a flood depth estimation model at a spatial resolution of ≈30 m, providing a comprehensive picture of maximum observed inundation depth across the MDB. Validation against 13 hydrodynamic model outputs for different parts of the MDB yielded a mean absolute error of 0.49 m, demonstrating reasonable accuracy and reliability of the dataset. The resulting dataset is best suited to system-wide analysis but might also be useful for those interested in the history of flooding at specific locations in the system. We provide the dataset, visualization tools, and examples to support ongoing research.

Unraveling the 2021 Central Tennessee flood event using a hierarchical multi-model inundation modeling framework

Flood prediction systems need hierarchical atmospheric, hydrologic, and hydraulic models to predict rainfall, runoff, streamflow, and floodplain inundation. The accuracy of such systems depends on the error propagation through the modeling chain, sensitivity to input data, and choice of models. In this study, we used multiple precipitation forcings (hindcast and forecast) to drive hydrologic and hydrodynamic models to analyze the impacts of various drivers on the estimates of flood inundation depth and extent. We implement this framework to unravel the August 2021 extreme flooding event that occurred in Central Tennessee, USA. We used two radar-based quantitative precipitation estimates (STAGE4 and MRMS) as well as quantitative precipitation forecasts (QPF) from the National Weather Service Weather Prediction Center (WPC) to drive a series of models in the hierarchical framework, including the Variable Infiltration Capacity (VIC) land surface model, the Routing Application for Parallel Computation of Discharge (RAPID) river routing model, and the AutoRoute and TRITON inundation models. An evaluation with observed high-water marks demonstrates that the framework can reasonably simulate flood inundation. Despite the complex error propagation mechanism of the modeling chain, we show that inundation estimates are most sensitive to rainfall estimates. Most notably, QPF significantly underestimates flood magnitudes and inundations leading to unanticipated severe flooding for all stakeholders involved in the event. Finally, we discuss the implications of the hydrodynamic modeling framework for real-time flood forecasting.

Hydrological-hydrodynamic nexus for predicting flood plain inundation: a case study in Pagladiya-Putimari catchment, India

Hydrological-hydrodynamic nexus for predicting flood plain inundation: a case study in Pagladiya-Putimari catchment, India

Low‐complexity floodplain inundation model performs well for ecological and management applications in a large river ecosystem

AbstractFlooding is a dominant physical process that drives the form and function of river‐floodplain ecosystems. Efficiently characterizing flooding dynamics can be challenging, especially over geographically broad areas or at spatial and temporal scales relevant for ecosystem management activities. Here, we empirically evaluated a low‐complexity geospatial model of floodplain inundation in six study segments of the Upper Mississippi River System (UMRS) by pairing spatially extensive, temporally limited and spatially limited, temporally extensive sampling designs. We found little evidence of systematic bias in model performance although discrepancies between model predictions and empirical data did occur locally. Assessments of model predictions revealed low segment‐wide discrepancies of wetted extent under contrasting flow conditions and agreement for inundation event detection and duration. Model performance for predicting event frequency and duration was similar among sites expected to exhibit contrasting patterns of hydrologic connectivity with the main channel. Our results suggest that low‐complexity models can efficiently characterize a critical physical process across geographically broad, complex river‐floodplain ecosystems. Such tools have the potential for advancing scientific understanding of landscape‐scale ecological patterns and for prioritizing management actions in large, complex river‐floodplain ecosystems like the UMRS.