Inundation Thresholds Research Articles

An improved method for computing tidal datums

Tidal datums are reference water levels describing the characteristic periodic variations in sea surface elevation relative to a vertical datum at a particular location. There are two common approaches for computing tidal datums: 1) the harmonic constituent approach, and 2) the peaks approach. Using a new method based on the peaks approach, tidal datums were computed and compared with theoretically equivalent constituent-based datums for a global set of 206 coastal tide gauges. The peak-based method described herein identifies high and low water turning points and then systematically classifies each according to semidiurnal, diurnal, and spring tidal cycles. The classified peaks and troughs in both predicted (excluding non-astronomical influences) and observed water level time series were averaged over a 19-year period. Tidal datums, such as Mean High Water Springs and Mean Higher High Water, are relied upon by many coastal authorities to define the tidal component of coastal inundation thresholds. Differences of >20 cm were found across tidal regimes and continents, demonstrating that the peaks approach is preferable over the constituent approach where such differences are non-negligible. An open source Tide Peaks Toolbox for use in MATLAB is presented for computing peak-based datums from any high frequency water level observation record.

Evaluation of tsunami inundation in the plain of Martil (north Morocco): Comparison of four inundation estimation methods

The Alboran Basin may be subject to tsunami hazards. If such an event were to occur, it is expected that the urbanised and densely populated areas of northern Moroccan coastline would be affected. Precise inundation hazard maps are needed for tsunami risk management in this region. In this article, we argue that the diversity of hazard mapping methods ensures the robustness of the scientific knowledge about the exposure of a territory. Hence, the main objective of this study is to analyse the exposure of the plain of Martil (north of Morocco), by using four hazard mapping methods to create inundation maps for two scenarios of tsunamis generated by extreme submarine mass failure (SMF) in the Alboran Sea, of 0.9 ​km3 and 3.8 ​km3 respectively. A digital terrain model of the plain was used to explore four methods of inundation mapping. The static method identified 4.32 ​km2 and 19.83 ​km2 of flooded areas for each scenario using water height values as inundation thresholds. The hybrid and the volumetric methods use the volume of water to determine the inundation extent. For the first scenario, 3.51 ​km2 of the plain were inundated using the hybrid method, and 20.11 ​km2 for the second scenario. The results of the volumetric methods are 2.32 ​km2 and 7.82 ​km2 respectively for the first and second scenario. Finally, the fourth method relies on numerical hydrodynamic modelling of tsunami inundation (Freshkiss3d® code). With this method, 4.55 ​km2 of the plain were flooded in the first scenario, and 24.12 ​km2 for the second. The comparison of the results highlights that the most sensitive areas to tsunami inundation are the lowest topographic ones, being the beaches and the wadis floodplains. This result raises questions on the current coastal development and the preparedness of its population, thus calling for more attention to engage on tsunami risk management related questions.

Phage-host-immune system dynamics in bacteriophage therapy: basic principles and mathematical models.

Phage therapy is progressively being recognized as a viable alternative to conventional antibiotic treatments, particularly in the context of multi-drug resistant bacterial challenges. However, the intricacies of the pharmacokinetics and pharmacodynamics (PKPD) pertaining to phages remain inadequately elucidated. A salient characteristic of phage PKPD is the inherent ability of phages to undergo replication. In this review, I proffer mathematical models that delineate the intricate dynamics encompassing the phage, the host organism, and the immune system. Fundamental tenets associated with proliferative and inundation thresholds are explored, and distinctions between active and passive therapies are accentuated. Furthermore, I present models that aim to illuminate the multifaceted interactions amongst diverse phage strains and bacterial subpopulations, each possessing distinct sensitivities to phages. The synergistic relationship between phages and the immune system is critically examined, demonstrating how the host's immunological function can influence the requisite phage dose for an optimal therapeutic outcome. A profound understanding of the presented modeling methodologies is paramount for researchers in the realms of clinical pharmacology and PKPD modeling interested in phage therapy. Such insights facilitate a more nuanced interpretation of dose-response relationships, enable the selection of potent phages, and aid in the optimization of phage cocktails.

Runnels mitigate marsh drowning in microtidal salt marshes.

As a symptom of accelerated sea level rise and historic impacts to tidal hydrology from agricultural and mosquito control activities, coastal marshes in the Northeastern U.S. are experiencing conversion to open water through edge loss, widening and headward erosion of tidal channels, and the formation and expansion of interior ponds. These interior ponds often form in high elevation marsh, confounding the notion applied in predictive modeling that salt marshes convert to open water when elevation falls below a critical surface inundation threshold. The installation of tidal channel extension features, or runnels, is a technique that has been implemented to reduce water levels and permit vegetation reestablishment in drowning coastal marshes, although there are limited data available to recommend its advisability. We report on 5 years of vegetation and hydrologic monitoring of two locations where a total of 600-m of shallow (0.15-0.30-m in diameter and depth) runnels were installed in 2015 and 2016 to enhance drainage, in the Pettaquamscutt River Estuary, in southern Rhode Island, United States. Results from this Before-After Control-Impact (BACI) designed study found that runnel installation successfully promoted plant recolonization, although runnels did not consistently promote increases in high marsh species presence or diversity. Runnels reduced the groundwater table (by 0.07-0.12 m), and at one location, the groundwater table experienced a 2-fold increase in the fraction of the in-channel tidal range that was observed in the marsh water table. We suggest that restoration of tidal hydrology through runnel installation holds promise as a tool to encourage revegetation and extend the lifespan of drowning coastal marshes where interior ponds are expanding. In addition, our study highlights the importance of considering the rising groundwater table as an important factor in marsh drowning due to expanding interior ponds found on the marsh platform.

EDM: An ensemble decision method for introducing meteorological forecast uncertainty into the disaster response decision process

In this study, an ensemble decision method (EDM) that ensures that disaster risk information includes sufficient meteorological forecast uncertainty and that decision supporting information retains sufficient disaster risk is proposed, thereby resolving the current issue of incomprehensive information. Visual presentations of real-time, multidimensional information are created to help decision-makers discern comprehensive information directly from ensemble warning charts, thereby enhancing the efficiency of operations and the quality of the decision process. The EDM comprises three steps: developing the disaster data model, developing ensemble warning charts, and developing the decision process to utilize the charts. In the first step, simulations are run using the forecast data of several ensemble members, rainfall inundation thresholds, and flooding risk hotspots in weather forecasts. In the second step, ensemble warning information is visualized by adopting three types of charts to present the disaster simulation results: a counties and cities inundation warning threat graph, a towns inundation warning time series chart, and a multidimensional inundation warning chart. In the third step, a decision process is designed to support decision-makers in assessing inundation threats, evaluating activation of disaster response operations, and determining response levels. To validate the proposed method, it is tested using data from three torrential rain events in 2019. The test results of the three torrential rain events show that the inundation warnings produced by the EDM better reflect actual inundation than those produced by the deterministic forecasts.

Identifying climate‐resistant vernal pools: Hydrologic refugia for amphibian reproduction under droughts and climate change

AbstractVernal pools of the northeastern United States provide important breeding habitat for amphibians but may be sensitive to droughts and climate change. These seasonal wetlands typically fill by early spring and dry by mid‐to‐late summer. Because climate change may produce earlier and stronger growing‐season evapotranspiration combined with increasing droughts and shifts in precipitation timing, management concerns include the possibility that some pools will increasingly become dry earlier in the year, potentially interfering with amphibian life‐cycle completion. In this context, a subset of pools that continues to provide wetland habitat later into the year under relatively dry conditions might function as ecohydrologic refugia, potentially supporting species persistence even as summer conditions become warmer and droughts more frequent. We used approximately 3000 field observations of inundation from 449 pools to train machine‐learning models that predict the likelihood of pool inundation based on pool size, day of the year, climate conditions, short‐term weather patterns, and soil, geologic and landcover attributes. Models were then used to generate predictions of pool wetness across five seasonal time points, three short‐term weather scenarios and four sets of downscaled climate projections. Model outputs are available through a website allowing users to choose the inundation thresholds, time points, weather scenarios and future climate projections most relevant to their management needs. Together with long‐term monitoring of individual pools at the site scale, this regional‐scale study can support amphibian conservation by helping to identify which pools may be most likely to function as ecohydrologic refugia from droughts and climate change.

Alteration of flood pulses by damming the Nenjiang River, China – Implication for the need to identify a hydrograph-based inundation threshold for protecting floodplain wetlands

Floodplain wetlands of low-gradient rivers are especially sensitive to alteration of hydrologic conditions. Although many studies have investigated changes in downstream hydrologic regimes caused by river dam construction, no study has specifically quantified the long-term effect of altered flood pulse on floodplain wetlands. Such knowledge is needed to develop effective dam operation strategies and plans for downstream wetland protection and restoration. We applied data time series from 1984 to 2018 to delineate the inundation extent of floodplain wetlands during the pre- (1984–2005) and post-dam (2006–2018) periods. Four segments of the 360-km river reach were selected to investigate how inundation frequency of floodplain wetlands responded to changes in flow regimes and flood pulse for both periods associated with dam operation. The results showed that the water area slightly increased as a result of recharging water from dam, while the inundation frequency of adjacent floodplain wetlands overall reduced because of lower magnitude of flood pulse. Inundation area of four segments show less variation during the post-dam period compared to the pre-dam period. These findings clearly indicate that decreased flood pulses caused by dam operations reduce both inundation frequency and areal extent of floodplain wetlands. Based on the findings, we propose an inundation threshold that can be used for dam operation to protect and restore river corridor and floodplain ecosystems.

Is the Risk of Sea Level Rise Capitalized in Residential Real Estate?

AbstractUsing a comprehensive database of coastal home sales merged with data on elevation relative to local tides, we compare prices for houses based on their inundation threshold under projections of sea level rise. The analysis separates the sensitivity of housing to rising seas from other confounding characteristics by exploiting cross-sectional differences in relative sea level rise due to vertical land motion. This provides variation in the expected time to inundation for properties of similar elevation and distance from the coast. In a variety of specifications and test settings, we find precisely estimated null results suggesting limited price effects.

Camo-maps: An efficient method to assess and project riparian vegetation colonization after a major river flood

Major river floods provide powerful physical disturbances that create and expand gravel bars and islands. Their barren surfaces are suitable for seedling colonization by plants including poplars (cottonwoods) and willows that grow to contribute rich wildlife habitats and other ecosystem services. Conversely, in locations such as through bridges, riparian woodlands would impede future flows, elevating flood stages and increasing damage. It is consequently useful to understand where opportunity versus hazard locations occur and this encourages monitoring and predictive modeling of vegetation colonization. Colonization is related to the river inundation patterns but hydrodynamic modeling is difficult for complex channels and irregular features. Here we present an alternative empirical approach based on mapping of actual inundation patterns from a sequence of aerial photographs at different river flows. Based on field inventory of seedling distributions of different plants, we estimated inundation thresholds for six progressively lower riparian cover types: woodland, shrubland, perennial herbaceous, ruderal annuals, transition and barren. These were coordinated with the inundation patterns, enabling predictive mapping of the different vegetation classes to produce ‘camo-maps’. These resemble camouflage with the irregular shapes and classification colors matching the vegetation types. The derived camo-maps were then compared with a lidar-based mapping of topography and vegetation structure. As an illustrative case study, we present the method for a large and complex gravel bar upstream from a bridge sequence and an expanded island below another bridge in Calgary Canada, where a hundred-year flood in June 2013 caused severe damage. The camo-maps reasonably represented the actual colonization patterns, although low flow years enabled some vegetation survival at lower positions than predicted. We present this as an effective and efficient empirical method to provide an alternative or complement to riparian vegetation projections based on hydrodynamic modeling.

Diagnosis of historical inundation events in the Marshall Islands to assist early warning systems

Inhabitants of low-lying coral atolls benefit from disaster risk reduction decision makers receiving early warnings of coastal inundation leading to heightened levels of alert and preparedness. Majuro, the capital of the Marshall Islands, is a coral atoll that experiences coastal inundation events on a near annual frequency and is likely to be exacerbated by sea-level rise, increasing the importance of early warning systems. However, current early warnings are not always provided for every inundation event. Inundation is driven by a combination of various oceanographic processes that contribute to sea level at the coastline, with the primary driver dependent on how extreme a particular process may be at the time. Incoming swell from distant storms and cyclones can trigger an inundation event, especially when coinciding with high spring tides and/or sea-level anomalies. Historical data from three directional scenarios were analysed to determine the critical values for offshore wave height, peak period, directional range, and sea level that had led to inundation in the past. Bulk wave statistics and static sea level were found to be sufficient information to identify the occurrence of an inundation event. These inundation thresholds serve as a reference to be used in conjunction with forecast models as an analogue for future events informing both the likelihood and impact. The analysis showed that inundation with a significant contributing swell factor propagates via three main routes, with approximately 50% occurring from the north-east. The two highest sea-level measurements on record both occurred during La Nina events, with both leading to inundation, suggesting that spring tides during La Nina events should exhibit a heightened level of alert for inundation at Majuro regardless of swell contribution.

Detecting inundation thresholds for dryland wetland vulnerability

Dryland wetlands receiving periodical floods are of key importance for ecological resilience. The inundation regime (i.e., frequency, duration, depth, and timing of inundation), is one of the major factors that determine the suitability of local conditions for specific wetland species. During droughts, inundation conditions can reach a threshold after which wetland vegetation could transition to dryland vegetation. This study analyses the response of vegetation to hydrologic variability in an arid wetland in Australia over a period of 22 years (including the Millennium drought) in order to identify inundation thresholds for transitions. We use numerical modelling, field observations and remote sensing data to relate continuous detailed simulations of the inundation regime with the response of patches of Common reed, Water couch and River red gum, three key vegetation associations in the study site. We focus in patches that were affected by the drought and presented dryland vegetation invasion as well as reference patches that remained healthy throughout the drought. On each patch, we compare annual and inter-annual simulated inundation regimes to the minimum inundation conditions that can support the specific vegetation, and we compute the percentage area of the patch that verifies minimum inundation for each year. We define this area percentage as minimum inundation index. This index is analysed in conjunction with Landsat derived information on green vegetation coverage (green Seasonal Fractional Cover) for the selected patches. We found that the minimum inundation index and inter annual frequency are able to describe the vegetation dynamics of the patches, which can be characterised by two distinct response modes that depend on a threshold value of the minimum inundation index. Inundation below the threshold noticeably leads to degraded vegetation, but the vegetation can recover quickly if this threshold is later maintained for one or two years. Values below the threshold for more extended periods (drought) result in a gradual decrease of wetland vegetation to almost complete disappearance after four years and subsequent dryland vegetation invasion.

Top-down and bottom-up controls on southern New England salt marsh crab populations.

Southern New England salt marsh vegetation and habitats are changing rapidly in response to sea-level rise. At the same time, fiddler crab (Uca spp.) distributions have expanded and purple marsh crab (Sesarma reticulatum) grazing on creekbank vegetation has increased. Sea-level rise and reduced predation pressure drive these changing crab populations but most studies focus on one species; there is a need for community-level assessments of impacts from multiple crab species. There is also a need to identify additional factors that can affect crab populations. We sampled crabs and environmental parameters in four Rhode Island salt marshes in 2014 and compiled existing data to quantify trends in crab abundance and multiple factors that potentially affect crabs. Crab communities were dominated by fiddler and green crabs (Carcinus maenas); S. reticulatum was much less abundant. Burrow sizes suggest that Uca is responsible for most burrows. On the marsh platform, burrows and Carcinus abundance were negatively correlated with elevation, soil moisture, and soil percent organic matter and positively correlated with soil bulk density. Uca abundance was negatively correlated with Spartina patens cover and height and positively correlated with Spartina alterniflora cover and soil shear strength. Creekbank burrow density increased dramatically between 1998 and 2016. During the same time, fishing effort and the abundance of birds that prey on crabs decreased, and water levels increased. Unlike in other southern New England marshes where recreational overfishing is hypothesized to drive increasing marsh crab abundance, we propose that changes in crab abundance were likely unrelated to recreational finfish over-harvest; instead, they better track sea-level rise and changing abundances of alternate predators, such as birds. We predict that marsh crab abundance will continue to expand with ongoing sea-level rise, at least until inundation thresholds for crab survival are exceeded.

Identifying critical inundation thresholds to maintain vegetation cover in stormwater treatment wetlands

Vegetation cover, specifically emergent macrophyte cover, is critical to the performance of constructed stormwater treatment wetlands which are widely used to protect receiving waterways. Maintenance of vegetation relies on a suitable water level regime, which in turn is governed by the hydraulic loading rate and efficiency of the outlet control structure. Wetland designers need to take these factors into account to avoid excessive depth and duration of inundation. We investigated the relationship between the water level regime and vegetation cover in 19 stormwater wetlands. We found a strong relationship between the median water level and vegetation cover, where vegetation cover was generally high (>80%) at median depths <0.35 m. Interestingly, poor outlet efficiency, rather than the hydraulic loading rate, was driving the water level regime. While this again highlights the importance of appropriate design and maintenance, we suggest that adjustable outlets in combination with real-time water level monitoring should be used to maintain a suitable water level regime in stormwater wetlands fed by dynamic urban catchments. The results of the study provide firm evidence for threshold depths for emergent macrophytes in stormwater wetlands which can be used to inform design guidelines.

Understanding the Impacts of Climate Change: an Analysis of Inundation, Marsh Elevation, and Plant Communities in a Tidal Freshwater Marsh

Tidal freshwater marshes around the world face an uncertain future with increasing water levels, salinity intrusion, and temperature and precipitation shifts associated with climate change. Due to the characteristic abundance of both annual and perennial species in these habitats, even small increases in early growing season water levels may reduce seed germination, seedling establishment, and late-season plant cover, decreasing overall species abundance and productivity. This study looks at the distribution of tidal freshwater marsh plant species at Jug Bay, Patuxent River (Chesapeake Bay, USA), with respect to intertidal elevation, and the relationship between inundation early in the growing season and peak plant cover to better understand the potential impacts and marsh responses to increased inundation. Results show that 62% of marsh plant species are distributed at elevations around mean high water and are characterized by narrow elevation ranges in contrast with species growing at lower elevations. In addition, the frequency and duration of inundation and water depth to which the marsh was exposed to, prior to the growing season (March 15–May 15), negatively affected peak plant cover (measured in end-June to mid-July) after a threshold value was reached. For example, 36 and 55% decreases in peak plant cover were observed after duration of inundation threshold values of 25 and 36% was reached for annual and perennial species, respectively. Overall, this study suggests that plant communities of tidal freshwater marshes are sensitive to even small systematic changes in inundation, which may affect species abundance and richness as well as overall wetland resiliency to climate change.

Land Surface Water Coverage Estimation with PALSAR and AMSR-E for Large Scale Flooding Detection

Land surface water cover (LSWC) PALSAR is obtained in this study by setting an inundated threshold using the interval estimation and Otsu's methods. By comparing the HH value (dB) obtained using these two methods along with image interpretation, the HH value with (μ + 3σ) is considered the most reasonable inundation threshold. After masking with μ + 3σ, LSWC of PALSAR was mapped and an exponential function with index NDFI (normalized difference frequent index) and NDPI (normalized difference polarization index) of AMSR-E corresponding to PALSAR LSWC was derived by applying the least squares method. It was found that the exponential regression curve could precisely represent the scatter points and the determination coefficient reached more than 0.8. Both NDFI and NDPI have a good fitting result with PALSAR LSWC. Spatial correspondence is finally discussed between AMER-E NDFI/NDPI LSWC and PALSAR LSWC. A high correspondence is shown between each map. It was also found that PALSAR slightly underestimated the inundated area because of the different PALSAR and AMSR-E mechanisms. Using more precise AMSR-E calibration by PALSAR, the availability and potential of AMSR-E LSWC for large scale flooding detection is indicated.

Mixed-sediment transport modelling in Scheldt estuary with a physics-based bottom friction law

In this study, the main object is to investigate the performance of a few new physics-based process models by implementation into a numerical model for the simulation of the flow and morphodynamics in the Western Scheldt estuary. In order to deal with the complexity within the research domain, and improve the prediction accuracy, a 2D depth-averaged model has been set up as realistic as possible, i.e. including two-way hydrodynamic-sediment transport coupling, mixed sand–mud sediment transport (bedload transport as well as suspended load in the water column) and a dynamic non-uniform bed composition. A newly developed bottom friction law, based on a generalised mixing-length (GML) theory, is implemented, with which the new bed shear stress closure is constructed as the superposition of the turbulent and the laminar contribution. It allows the simulation of all turbulence conditions (fully developed turbulence, from hydraulic rough to hydraulic smooth, transient and laminar), and the drying and wetting of intertidal flats can now be modelled without specifying an inundation threshold. The benefit is that intertidal morphodynamics can now be modelled with great detail for the first time. Erosion and deposition in these areas can now be estimated with much higher accuracy, as well as their contribution to the overall net fluxes. Furthermore, Krone’s deposition law has been adapted to sand–mud mixtures, and the critical stresses for deposition are computed from suspension capacity theory, instead of being tuned. The model has been calibrated and results show considerable differences in sediment fluxes, compared to a traditional approach and the analysis also reveals that the concentration effects play a very important role. The new bottom friction law with concentration effects can considerably alter the total sediment flux in the estuary not only in terms of magnitude but also in terms of erosion and deposition patterns.

Observations and estimates of wave‐driven water level extremes at the Marshall Islands

AbstractWave‐driven extreme water levels are examined for coastlines protected by fringing reefs using field observations obtained in the Republic of the Marshall Islands. The 2% exceedence water level near the shoreline due to waves is estimated empirically for the study sites from breaking wave height at the outer reef and by combining separate contributions from setup, sea and swell, and infragravity waves, which are estimated based on breaking wave height and water level over the reef flat. Although each component exhibits a tidal dependence, they sum to yield a 2% exceedence level that does not. A hindcast based on the breaking wave height parameterization is used to assess factors leading to flooding at Roi‐Namur caused by an energetic swell event during December 2008. Extreme water levels similar to December 2008 are projected to increase significantly with rising sea level as more wave and tide events combine to exceed inundation threshold levels.

Drift and retention of pelagic spawning minnow eggs in a regulated river

ABSTRACTLong‐distance drift of eggs and larvae has been identified as a possible cause of downstream displacement and poor recruitment of the endangered Rio Grande silvery minnow (Hybognathus amarus; silvery minnow). Seven experiments were conducted using artificial eggs to estimate silvery minnow egg drift and retention in the Albuquerque and Isleta reaches of the regulated Middle Rio Grande, New Mexico, USA over a range of flows during expected spawning times. Bead retention varied by reach, discharge, and shape of the hydrograph. Highest retention (6.9 and 9.7% per km in the Albuquerque and Isleta reaches, respectively) occurred on the ascending limb of a high flow in areas where there was substantial floodplain inundation. Retention was maximized at different flows in each reach (97 and 140 m3/s, respectively), possibly associated with reach‐specific floodplain inundation thresholds. Lowest retention in each reach (2.1 and 1.7%, respectively) occurred on the descending limb of low and high flows, respectively. Of the silvery minnow eggs produced in the combined Albuquerque and Isleta reaches in 2005, 8–14% are predicted to have been retained in the Albuquerque Reach (67 km) and 49–83% in the Isleta Reach (86 km) based on the distribution of adult fish and measured bead retention rates. Although silvery minnow propagules are capable of drifting long distances, our study suggests that considerable retention occurs in the Middle Rio Grande. Habitat restoration to increase channel habitat complexity, and flow management to promote floodplain inundation should help to retain a greater proportion of propagules in upstream reaches. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Quantitative Models of In Vitro Bacteriophage–Host Dynamics and Their Application to Phage Therapy

Phage therapy is the use of bacteriophages as antimicrobial agents for the control of pathogenic and other problem bacteria. It has previously been argued that successful application of phage therapy requires a good understanding of the non-linear kinetics of phage–bacteria interactions. Here we combine experimental and modelling approaches to make a detailed examination of such kinetics for the important food-borne pathogen Campylobacter jejuni and a suitable virulent phage in an in vitro system. Phage-insensitive populations of C. jejuni arise readily, and as far as we are aware this is the first phage therapy study to test, against in vitro data, models for phage–bacteria interactions incorporating phage-insensitive or resistant bacteria. We find that even an apparently simplistic model fits the data surprisingly well, and we confirm that the so-called inundation and proliferation thresholds are likely to be of considerable practical importance to phage therapy. We fit the model to time series data in order to estimate thresholds and rate constants directly. A comparison of the fit for each culture reveals density-dependent features of phage infectivity that are worthy of further investigation. Our results illustrate how insight from empirical studies can be greatly enhanced by the use of kinetic models: such combined studies of in vitro systems are likely to be an essential precursor to building a meaningful picture of the kinetic properties of in vivo phage therapy.

A reach‐scale remote sensing technique to relate wetland inundation to river flow

AbstractKnowledge of the relationship between river flow and wetland inundation at a reach‐scale is important for effective flow management, particularly, for environmental outcomes. Historical remotely sensed data, such as Landsat TM, provide the potential to determine the relationship between flow and wetland inundation for extended river reaches. In this paper we apply, adapt and evaluate a technique using sets of before‐flood and after‐flood image pairs to relate river flow to wetland inundation on a 640 km reach of the mid‐Murrumbidgee River, Australia. Stratification of the complete reach into relatively uniform sub‐reaches on the basis of hydrology and geomorphology was undertaken as a key pre‐analysis step. Analysis of flood wave attenuation within each sub‐reach showed that flood peaks entering and leaving a reach were highly correlated. Therefore, we argue that a flood peak measured at a single gauge within the reach can be used to provide a reliable indication of the behaviour of similar sized floods within the reach. The remote sensing technique proved capable of producing a model relating wetland inundation thresholds to flood peak discharge for each sub‐reach within the extended river reach. Although the model simplifies the complex relationship between river flow and wetland inundation, reliable key wetland inundation flow thresholds were determined. Copyright © 2008 John Wiley &amp; Sons, Ltd.