Flood Phase Research Articles

Body size and population dynamics of annual fishes from temporary wetlands in Southern Brazil

Annual fishes live exclusively in temporary wetlands where several species coexist. Understanding how annual fishes cohabit in small and isolated pools is still a challenge. In this study, we aimed to examine the prediction that annual fish assemblages in temporary pools in Southern Brazil are structured by temporal differences in body size, specific growth rate and density. Two–three fish species coexisted in each pool. The most abundant and frequent species were Cynopoecilus melanotaenia and Austrolebias nigrofasciatus, while A. wolterstorffi was less abundant and rare. The species differed significantly in body size throughout the flooding phase and showed similar growth patterns, with higher specific growth rates in the first months of flooding and a reduction in growth rate thereafter. The monthly average densities of A. nigrofasciatus and C. melanotaenia did not differ over time, but they were higher than values observed for A. wolterstorffi. Our results provide evidence for hatching synchrony, similar specific growth rates and densities among the most abundant species and differences in body sizes among all species that are more evident after adulthood, suggesting that differences in body size mediate the coexistence of annual fishes in temporary pools.

Mobilization of Crude Oil in Porous Media With Oil-Soluble Surfactant Delivered by Hydrosoluble Micelles

In this work, an oil-soluble surfactant was studied to enhance crude oil mobilization in a cryolite-packed miniature bed. The cryolite packed bed provided a transparent, random porous medium for observation at the microscopic level. In the first part of the paper, oil-soluble surfactants, Span 80 and Eni-surfactant (ES), were dissolved directly into the crude oil. The porous medium was imbued with the crude oil (containing the surfactants), and de-ionized water was the flooding phase; in this experiment, the system containing ES had the best performance. Subsequently, sodium dodecyl sulfate (SDS), a hydrosoluble surfactant, was used to solubilize the ES, with the SDS acting as a carrier for the ES to the contaminated porous media. Finally, the SDS/ES micellar solutions were used in oil-removal tests on the packed bed. Grayscale image analysis was used to quantify the oil recovery effectiveness for the flooding experiments by measuring the white pixel percentage in the packed bed images. The SDS/ES flooding mixture had a better performance than the SDS alone.

Geoarchaeological evidence of landscape transformations at the Neolithic and Bronze Age settlement of Nea Raedestos in the Anthemous River valley, central Macedonia, Greece

AbstractA paleoenvironmental reconstruction of the landscape of Nea Raedestos Toumba in the Anthemous River valley in central Macedonia, Greece is undertaken using multidisciplinary geoarchaeological methods. The archaeological site is a settlement mound (tell or toumba) that dates to the Neolithic period and the Bronze Age. The tell’s location on the alluvial plain prompted a multidisciplinary investigation to reconstruct the influence of landscape changes on prehistoric settlements in the valley with an emphasis on alluvial sequences. An electrical resistivity tomography survey and three cores were drilled to study the sedimentary environments in and around the archaeological site. Sedimentologic and palynological analysis combined with accelerator mass spectrometry radiocarbon dating show that the oldest habitation layers at the site, from the Middle and Late Neolithic, were located next to a small, periodically drying water body surrounded by ruderal vegetation. Diatom analysis suggests that this water body was supplied by saline/brackish groundwater. The water body was open until the Early Bronze Age, when it was filled and buried by floodplain sediments. This flooding phase at Nea Raedestos likely occurred at the same time as an increase in fluvial aggradation in the neighboring Thessaloniki Plain, which is dated to the beginning of the third millennium BC.

Differential sediment trapping abilities of mangrove and saltmarsh vegetation in a subtropical estuary

Saltmarsh and mangrove are common coastal wetland types and their ability to enhance deposition has been investigated extensively, but rarely compared directly. This study carried out in situ observations to compare the sediment transport processes between a bare mudflat, a mangrove stand and a saltmarsh stand within a subtropical estuary. Turbidity variations over the latter portion of a spring tide were recorded, alongside measurements of flow data, to estimate sediment trapping by hydraulic forces under similar hydroperiods. In addition, vegetation was transplanted to compare the direct sediment trapping by high-standings and short-seedlings. The suspended sediment concentration (SSC) time series showed an overall reduction between the bare mudflat and the vegetated flats. Suspended sediment flux estimates revealed that a considerable amount of sediment was trapped by the saltmarsh and the mangrove edges. The flux estimates find that the saltmarsh edge is more efficient than the mangrove edge in trapping sediments transported normal to the edge. The sediment trapping mechanisms were considered based on two approaches: the hydrodynamic related sediment settling and direct trapping by vegetation. The calculation of deposition tendency showed that the presence of vegetation altered the flow direction and the tidal asymmetry of the deposition process, resulting in a higher deposition tendency during the flood phase to enhance sediment settling. In addition to sediment settling, vegetation surfaces were found to trap sediments directly. In combination with rinsing by precipitation, these trapped sediments accumulated on the bed and contributed to the deposition. Against the background of similar inundation periods, the saltmarsh grass showed a greater sediment trapping ability than the mangrove trees, in terms of both the hydraulic sediment trapping and the direct trapping by vegetation surface.

Effects of Flood Pulse Dynamics on Functional Diversity of Macrophyte Communities in the Pantanal Wetland

Environmental variations and plant traits can act as a filter in plant communities, selecting better-adapted species. In wetlands, macrophytes display physiological, morphological and life history plasticity that allows them to adapt to flood dynamics reflecting habitat filtering. Our aim was to evaluate if the functional diversity of macrophytic community varies between the flood phases, noting whether water factors influence the functional diversity and whether the traits that denote adaptation are associated with these phases. We evaluated 11 morphological traits of macrophytes. The floristic survey within and on the edge of twenty ponds was carried out on a monthly basis and the water parameters were measured for two years. The functional diversity was lower in the ‘drought’ and increased over the flood cycle reaching maximum values in the ‘water recession’ phase. ‘Drought’ acted as a filter by selecting only a few adapted species and the ‘water recession’ acted as a transition area combining favourable conditions for the species of both dry and flood. The trait that contributed most to differentiate the functional groups was the life form. We conclude that the environments under spatial and temporal changes support different communities with different functional characteristics.

Observations of Mud‐Induced Periodic Stratification in a Hyperturbid Estuary

AbstractThis study presents new observations of fluid mud transport and of the interaction between mud‐induced stratification and the flow. Data collected in a hyperturbid estuarine tidal channel reveal details of the intratidal entrainment asymmetry, characterized by quasi‐instantaneous entrainment and upstream pumping of mud during flood, and a gradual reduction of layer thickness by shear dispersion during ebb. Rapid restratification early during the flood phase restores the predominant two‐layer structure and delimits the transport period, which is then significantly shorter than the overall flood duration. The hydraulic cross section is reduced, causing an increase of the salinity intrusion into the estuary at the end of the flood. The fluid mud layer occupies on average 40% of the water depth, and stratification exceeds that of highly stratified salt wedge estuaries. These data show how mud‐induced periodic stratification influences flow structure and sediment transport and thereby contribute to the understanding of the dynamics of hyperturbid estuaries.

Wave-induced Maintenance of Suspended Sediment Concentration during Slack in a Tidal Channel on a Sheltered Macro-tidal Flat, Gangwha Island, Korea

A field campaign was conducted to better understand the influence of wave action, in terms of turbulence and bed shear stress, on sediment resuspension and transport processes on a protected tidal flat. An H-frame was deployed in a tidal channel south of Gangwha Island for 6 tidal cycles during November 2006 with instrumentation including an Acoustic Doppler Velocimeter, an Acoustic Backscatter System, and an Optical Backscatter Sensor. During calm conditions, the current-induced shear was dominant and responsible for suspending sediments during the accelerating phases of flood and ebb. During the high-tide slack, both bed shear stress and suspended sediment concentration were reduced. The sediment flux was directed landward due to the scour-lag effect over a tidal cycle. On the other hand, when waves were stronger, the wave-induced turbulence appeared to keep sediments in suspension even during the high-tide slack, while the current-induced shear remained dominant during the accelerating phases of flood and ebb. The sediment flux under strong waves was directed offshore due to the sustained high suspended sediment concentration during the high-tide slack. Although strong waves can induce offshore sediment flux, infrequent events with strong waves are unlikely to alter the long-term accretion of the protected southern Gangwha tidal flats.

Dramatic source-sink transition of N2O in the water level fluctuation zone of the Three Gorges Reservoir during flooding-drying processes.

Biogeochemical cycling of nitrous oxide (N2O), a significant greenhouse gas (GHG), can influence global climate change. The production and emission of N2O mediated by hydrological regimes is particularly active in water level fluctuation zones (WLFZs). However, the hydrological mechanisms affecting N2O transformation and production across the water-sediment micro-interface remain unclear. In this study, intact sediment cores from the WLFZs of the Three Gorges Reservoir (TGR) were incubated for 24days in a laboratory microcosm to identify the effects of the flooding-drying processes on the yield and emission of N2O. Results showed a source-sink transition of N2O in the first 1.5days during the flooding period, with the water column subsequently acting as a sink relative to the atmosphere in the following experimental period. The source-sink transition was ascribed to changes in oxygen concentration in the water column and sediment regulation of NO3--N transformation, resulting in denitrification and N2O production. Preliminary estimates on the mass budget of N2O in a typical WLFZs of the TGR showed slight emission fluxes, ranging from 13.08 to 43.08μmolm-2 from flooding period to drying process. Although these N2O emissions were relatively low, the emission peak detected during the initial period (first 1.5 days) of the flooding phase provides important knowledge on the mitigation of GHG emissions from hydropower sources, which should be incorporated into future reservoir operations.

Visualization study on capillary-spreading behavior of liquid droplet in vertically aligned carbon nanotube array

Vertically aligned carbon nanotube (CNT) arrays exhibit distinct wetting characteristics. Thus, they are a promising solution for many applications such as heat-pipe wicks. In this study, the dynamic behavior of liquid-droplet spreading via capillary action in a vertically aligned CNT array has been investigated experimentally and theoretically. Two groups of CNT array with heights of 150 μm and 250 μm were tested. Two organic solvents, namely ethanol and acetone, were selected as the wetting liquids because of their good wettability with the as-grown CNTs. A visualization system equipped with a high-speed camera was used to record the capillary-spreading process. The results of the CNT array with different array heights showed two distinct modes of spreading: a steady uniform mode and an unsteady random mode. In the unsteady mode, the liquid predominantly spreads above the array. In the steady mode, the spreading process can be divided into three phases based on the different dominating effects. After the first flooding phase, the spreading in the second phase was found to follow the Lucas–Washburn model, whereas the third phase can be described using a constant evaporation-rate model. The self-assembly behavior was observed using an SEM after the wetting experiments. Honeycomb-shaped microstructures were formed spontaneously in the precursor-film region, whereas striped lines were observed on the front end of the contact line.

Reproductive phenology of Polygonum hispidum Kunth and P. punctatum Elliott (Polygonaceae), in response to the flooding cycle in the Pantanal, Brazil

In flood-driven environments the life cycles of organisms are regulated in function of the water regime. The objective of this work is to analyse the phenophases of flowering and fructification of two species of amphibious aquatic macrophytes, Polygonum hispidum Kunth and P. punctatum Elliott, with regard to the flooding cycle of the Brazilian Pantanal. We collected monthly data in 26 plots of 20 ponds during two years. The flooding phases were classified as drought, rising, flood, and receding. The periods with an abundance of water (rising, flooding, and receding) were the most important for reproduction. Both species bear fruits at flood, when the water is deepest and remains until receding, and most seeds are dispersed. The synchrony between reproductive cycles and these flood phases suggests the importance of seasonality in the reproductive patterns of these species.

Turning the tide: comparison of tidal flow by periodic sea level fluctuation and by periodic bed tilting in scaled landscape experiments of estuaries

Abstract. Analogue models or scale experiments of estuaries and short tidal basins are notoriously difficult to create in the laboratory because of the difficulty to obtain currents strong enough to transport sand. Our recently discovered method to drive tidal currents by periodically tilting the entire flume leads to intense sediment transport in both the ebb and flood phase, causing dynamic channel and shoal patterns. However, it remains unclear whether tilting produces periodic flows with characteristic tidal properties that are sufficiently similar to those in nature for the purpose of landscape experiments. Moreover, it is not well understood why the flows driven by periodic sea level fluctuation, as in nature, are not sufficient for morphodynamic experiments. Here we compare for the first time the tidal currents driven by sea level fluctuations and by tilting. Experiments were run in a 20 × 3 m straight flume, the Metronome, for a range of tilting periods and with one or two boundaries open at constant head with free inflow and outflow. Also, experiments were run with flow driven by periodic sea level fluctuations. We recorded surface flow velocity along the flume with particle imaging velocimetry and measured water levels along the flume. We compared the results to a one-dimensional model with shallow flow equations for a rough bed, which was tested on the experiments and applied to a range of length scales bridging small experiments and large estuaries. We found that the Reynolds method results in negligible flows along the flume except for the first few metres, whereas flume tilting results in nearly uniform reversing flow velocities along the entire flume that are strong enough to move sand. Furthermore, tidal excursion length relative to basin length and the dominance of friction over inertia is similar in tidal experiments and reality. The sediment mobility converges between the Reynolds method and tilting for flumes hundreds of metres long, which is impractical. Smaller flumes of a few metres in length, on the other hand, are much more dominated by friction than natural systems, meaning that sediment suspension would be impossible in the resulting laminar flow on tidal flats. Where the Reynolds method is limited by small sediment mobility and high tidal range relative to water depth, the tilting method allows for independent control over the variables flow depth, velocity, sediment mobility, tidal period and excursion length, and tidal asymmetry. A periodically tilting flume thus opens up the possibility of systematic biogeomorphological experimentation with self-formed estuaries.

Study on coupled dynamics of ship and flooding water based on experimental and SPH methods

The present paper studies the fluid dynamics during the flooding of a damaged ship numerically and experimentally. Attention is focused on the fluid flow characteristics and the fluid-structure interactions. The Smoothed Particle Hydrodynamics (SPH) method with an improved boundary treatment is established, which is able to capture the flow behaviors effectively. Fairly good agreement is obtained between the computational and experimental results. Based on the SPH method, the simulations are carried out for the flooding of a damaged ship with different opening sizes, opening positions, and numbers of the flooding cabins. Besides, the effects of the wave are also taken into account. The fluid behaviors are described and analyzed in detail. It is found that, during the first phase of flooding, an inflow jet with a large velocity is formed, significantly influencing the inner flows and the ship responses. During the progressive flooding phase, sloshing, crushing of the free surface, wave breaking, and vortex shedding are observed which are coupled with the ship motions. In addition, some relevant conclusions are enclosed for the motion laws of the damaged ship. This work provides physical insight into the flooding of the damaged ship, which is helpful to understand the coupled dynamics of the ship and flooding water.

Patterns, drivers and implications of dissolved oxygen dynamics in tropical mangrove forests

Estuarine mangrove forests regulate and facilitate many ecological processes, and provide nursery ground for many commercially important species. However, mangroves grow in sediments with high carbon loading and high respiration rates which can potentially influencing the dissolved oxygen (DO) dynamics of tidal water flowing into mangrove forests, as bacteria strip DO from the incoming water to carry out metabolic functions. In turn this is likely to influence the way nekton and other aquatic organisms utilize mangrove forests. Despite these possibilities, previous work has focused on looking at DO dynamics within mangrove creeks, with little research focusing on understanding DO dynamics within the mangrove forests themselves during tidal inundation or of DO levels of pools within the forest remaining once the tide has ebbed. The present study investigates the pattern in DO at various distances within an estuarine Rhizophora stylosa forest in tropical north Queensland. DO levels were recorded at 5 min interval over 2 days and multiple tidal cycles, data were collected between 2013 and 2014 for a total of 32 tidal cycles encompassing multiples seasons and tidal amplitudes. There were substantial fluctuations in DO, often varying from normoxic to hypoxic within the same tidal cycle. A range of factors influenced DO dynamics, in particular: tidal height, amount of sunlight, tidal phase, and distance from the outer edge of the mangrove forest. In fact, spring tides tend to have high DO saturation, particularly during the flooding phase, however as the tide starts ebbing, DO depletes rapidly especially in areas further inside the forest. Moreover during tidal disconnection the remnant pools within the forest quickly became anoxic. These variations in DO suggest that the use of mangrove forests by animals is likely to be constrained by their ability to withstand low DO levels, and provides a plausible explanation for the apparent paucity of benthic organism observed inside similar mangrove forest in previous studies of South Pacific mangroves. Low DO levels coupled with low densities of benthic prey also provides a likely explanation for the limited utilisation of landwards areas of these forests by fish and other nekton.

Short-term variations in surface water properties in the Sundarban Estuarine System, India

High resolution measurements were carried out to understand the short-term (<1 h) variability of surface water quality parameters in mangrove-dominated Sundarban Estuarine System of West Bengal, India during flood phases of spring-neap tidal cycle in a peak monsoon season August 2014. We observed that tidal propagation of both phases strongly influenced the water quality properties. During spring tide salinity, DO, pH, nitrate, phosphate, silicate, chlorophyll a and phaeopigments concentration exhibited increasing trends; whereas at neap tide nitrate, ammonia and chlorophyll a showed decreasing trends. Average nutrient concentrations were much higher during neap tide than spring tide. All the measured water quality parameters varied in every 15-min interval influenced by the tidal current, mangrove litter fall, re-suspension of bottom sediment and river runoff. The effect of tidal amplitude was observed to be the important factor in determining the variability in most of the water quality parameters.

Sedimentary infilling of bedrock-controlled palaeo-embayments off Cape Trafalgar, Strait of Gibraltar (Gulf of Cadiz)

This study investigates two bedrock-controlled palaeo-coastal embayments on the Barbate Platform off Cape Trafalgar near the Strait of Gibraltar (Gulf of Cadiz shelf, SW Iberian Peninsula), aiming to reveal their infilling dynamics and the influence of rocky outcrops on shallow-water hydrodynamics and sediment transport. The approach relies on detailed multibeam bathymetric data, high-resolution seismic profiles and tidal current simulations. Elongated rocky outcrops formed a palaeo-coast when sea level was approximately 35 to 20 m below that of the present day, and bound a relatively flat area. However, the seismic profiles enabled to distinguish two main troughs (A and B) that were infilled following a distinctive evolution during the last transgression. Five seismic units were identified (I to V, from base to top). Deposit A is composed of seismic units II to V and is interpreted as a marine embayment infill, here termed the Barbate palaeo-embayment (BPE). Deposit B is composed of seismic units I to IV and is interpreted as a palaeo-valley infill, here termed the Barbate palaeo-valley (BPV). The complex internal stratigraphic architecture depicts an overall evolution from tidal/fluvial deposits to shallow-water marine deposits. Most significant is the occurrence of coupled tidal flats/estuarine sand bars constituting the infilling of the BPE; this suggests the persistence of a high-energy current in a shallow, confined embayment, which was amplified by the rocky outcrop constrictions and possibly facilitated by the episodic movement of a normal fault. In contrast to this active setting, the nearby straight and narrow BPV was subjected to lower-energy infilling dynamics during its initial flooding phases. There, tidal activity was possibly reduced by the straight morphology of the valley and the occurrence of a topographic constriction (i.e. the Barbate Passage) at the mouth of the valley.

The Holocene floods and their affinity to climatic variability in the western Himalaya, India

The present study in the middle Satluj valley explores the sedimentary records of past floods with an objective to understand the climatic processes responsible for their genesis. Based on lithostratigraphy, sedimentology, and grain size variability, 25 flood events are identified. The geochemical data indicate that the flood sediments were mostly generated and transported from the higher Himalayan crystalline and the trans-Himalaya. Our study suggests that the floods were generated by Landslide Lake Outburst Floods (LLOFs) during extreme precipitation events. However, the existing database does not allow us to negate the contribution from Glacial Lake Outburst Floods (GLOFs). Field stratigraphy supported by optical chronology indicates four major flood phases that are dated to 13.4–10.4, 8.3–3.6, 2.2–1.4, and <1.4ka (kilo-annum). These phases correspond to the cooler and less wet conditions and broadly correlate with the phases of negative Arctic Oscillation (−AO) and negative North Atlantic Oscillation (−NAO). Thus, implying coupling between the moisture-laden monsoon circulation and southward penetrating mid-latitude westerly troughs for extreme precipitation events and consequent LLOFs. Additionally, a broad synchronicity in Holocene floods between the western Himalaya and across the mid-latitudinal region (30°N–40°N) suggests a synoptic scale Arctic and Atlantic climate variability.

Dynamics of sediment disturbance by periodic artificial discharges from the world's largest tidal power plant

To investigate the dynamics of sediment disturbance near the world's largest Sihwa tidal power plant (TPP), two mooring observations have been conducted. The mooring results show that current velocity and suspended sediment concentration (SSC) were significantly disturbed over various time scales. On the short-term (flood−ebb) time scale, resuspension of bottom sediment is mainly controlled by the strong jet-flow (>2 m s−1) and resulting anticlockwise rotating vortex associated with the artificial discharge. During ebb phase, the strong flow resulted in suspension of high-concentration near-bed sediment and seaward transport of the suspended sediment. After turning to flood phase, the vortex produced secondary SSC peaks, transporting the suspended sediment toward the Sihwa TPP. The most active suspension of bed sediment predominantly occurred during 1–2 h immediately after the start of artificial discharge. For the fortnightly (spring−neap) time scale, SSC during spring tide was approximately 2–5 times higher than that during neap tide. During the combined period of ebb and spring tides, in particular, the periodic artificial discharge can enhance the responses of SSC in the vicinity of Sihwa TPP.

Spawning calls by zulega, Prochilodus argenteus, a Brazilian riverine fish

We studied calling and spawning of the potamodromous fish zulega (Prochilodus argenteus, Prochilodontidae) in the Sao Francisco River (SFR), Brazil. The study reach was the 143 river km (rkm) downstream from Tres Marias Dam (TMD), but most effort was at the Pontal spawning ground (PSG). PSG is located in the SFR at the mouth of the first major tributary (Abaete River), 33 rkm downstream from TMD. Abiotic factor in the flooding by the Abaete River due to rain was the major trigger for spawning by zulega at PSG. Size of PSG increased with magnitude of Abaete River flooding. Zulega males called 24 h a day, but longer periods of calling occurred in the daytime than at night. Zulega males called in lek choruses, apparently in discrete arenas, and did not school while calling. Spawning calls from zulega occurred in the entire 110 rkm reach of the SFR downstream from PSG, but only during major flooding from the Abaete River. The spawning trigger factor was absent in SFR water draining from TMD. A large spillage of 1700 m3*s−1 from this dam that was warmer than temperatures during zulega spawning inhibited spawning possibly due to alteration of the thermal regime of the Sao Francisco River. The best time for spillage to restore zulega fisheries downstream of TMD may be in the decreasing phase of a natural flood, but further tests are needed. Damming the Abaete River may eliminate the spawning trigger for zulega at PSG and downstream in the SFR.

Physical and sedimentary processes on the tidal flat of central Jiangsu Coast, China: Headland induced tidal eddies and benthic fluid mud layers

An 11-tidal-cycle record time series of current, wave, suspended-sediment, and bed-level characteristics was analyzed to identify physical and sedimentary processes on the tidal flat of Jiangsu Coast, China. A tripod observation system was placed near the transition between mid and upper tidal flat south of a newly constructed harbor for hydrodynamic and sediment dynamic measurements from 27 Apr 2013 to 3 May 2013. The observations confirm the stable longshore northward (ebb direction) current s with residual velocities ~59.2° anti-clockwise from the offshore direction. This phenomenon can be attributed to the effects of headland (the Harbor) induced tidal eddies based on comparable frictional length scale and the headland length scale. Benthic fluid mud layers occurred in 2 of 11 tidal cycles, with the conditions of strong waves during the flood phase. The fine sediment was resuspended by the waves and currents from the lower area, transported upward and concentrated at the observation station, resulting in the formation of a fluid mud layer with thickness of ~15cm and SSC of ~8kg/m3 at 10cmasb. Once formed, the fluid mud layer dramatically modified the flow structure, showing a large reduction of current speed from 20cmasb to 10cmasb, when the gradient Richardson number was around the critical value of 0.25, inferring that sufficient turbulence from waves and currents exists to maintain fluid mud suspension. The fluid mud processes appear to occur episodically and may play an important role of sediment dynamics on the tidal flat.

On the effects of non-watertight doors on progressive flooding in a damaged passenger ship

The intermediate stages of flooding can be very dangerous, especially if the flooding is asymmetric. Modern passenger ships have complex transverse and vertical subdivisions inside the watertight compartments. These structures are often needed for fire integrity, and they are not watertight. However, in the event of damage they may have a significant effect on the flooding process. Time-domain flooding simulation, combined with the latest research on the leakage and collapse of non-watertight structures, enables a very realistic approach on the intermediate phases of flooding. In this paper the effects of random variation in the status of the fire doors (open or closed) and the applied parameters for modelling leaking and collapsing of closed non-watertight doors are studied. The results indicate that the status of a non-watertight door can have enormous effects on the progress of flooding, and especially on the time-to-capsize. On the other hand, variation in the modelling of leakage and collapse parameters of closed doors had much smaller effects. The results can be utilized in planning a conservative combination of non-watertight door statuses in time-domain damage stability analysis for ship design, and in the assessment of uncertainty of the results from such computations.