Lateral Flooding Research Articles

Export and bioaccumulation of methylmercury in streams draining distinct soils in the Central Brazilian Amazon, 2012-2013

BackgroundUpland forest streams of the Central Amazon are unique aquatic systems.These small streams have short, unpredictable and multimodal flood-pulses that are influenced by local rainfall. The biogeochemical cycles in these systems are almost unknown. This study investigated the role of soil type on the export and bioaccumulation of methylmercury (MeHg) in upland forest streams of the Central Amazon during a complete annual cycle. Basic ProceduresLimnological measurements and water samples for MeHg analyses were collected monthly from October 2012 to October 2013 in two headwater streams drained by different soil types, spodzol (Campina Stream) and oxisol (Barro Branco Stream), in natural forest reserves. Shrimp and fish were collected for total mercury (THg) in April 2013 in both streams. Main findingsMeHg in water varied from 0.04 to 0.50 ng/L in the Campina Stream and between <detection limit and 0.04 ng/L in Barro Branco Stream. Physical characteristics of soils and the interaction between mercury and organic matter influenced the methylation of mercury and its export to the streams. In both streams, MeHg export was highest during the rainy season, probably due to soil leaching, lateral flooding and soil hydromorphism during this period, processes conducive to mercury methylation and export. THg in shrimps (omnivores) and carnivorous fish, which fed on aquatic food items, reflected the MeHg differences between streams while those in insectivorous fish, feeding on allochthonous food items, did not. Principal ConclusionsMeHg dynamics in streams were influenced by the physical characteristics of basin soils and by local seasonal rainfall.

Experimental study on lateral flooding for enhanced oil recovery in bottom-water reservoir with high water cut

The regular enhanced oil recovery (EOR) methods in bottom-water reservoir aim to increase the vertical sweep efficiency. After multicycle chemical injection, the injected slug cannot effectively control the bottom water coning in the presence of fully developed water channel, decreasing the sweep efficiency and lowering economic efficiency. To improve the development effect of bottom-water reservoir, lateral flooding is proposed as a more cost-effective EOR technique by displacing the oil formation horizontally. In this study, three lateral flooding tests were performed in a three-dimensional physical model based on the geometric similarity criterion. Bottom-water reservoirs were simulated by sandpacking oil and water formations according to the parameters of the target oil reservoir. The bottom-water energy was supplied by an ISCO constant pressure, and the lateral flooding was conducted by an ISCO constant rate pumps. The oil recovery, water cut, pressure drop, and saturation variation maps obtained from these tests were recorded and analyzed. A comparison of these results between different crosslinked polymer slug tests shows that the improved oil recovery by lateral waterflooding can be mainly attributed to a significant increase in horizontal sweep efficiency. After 0.3 PV crosslinked polymer injection, about two-thirds of that was used to shut off the main water channels; the chemical packer, formed by the surplus polymer spreading along the oil/water interface under the drive of lateral injection, can inhibit bottom water from coning into the oil formation and prevent the crossflow. The 0.2, 0.3, and 0.4 PV crosslinked polymer injection can increase oil recovery by as much as 11.35, 36.23, and 39.74% of the original oil-in-place (OOIP), respectively. This confirms that lateral flooding is an efficient EOR method in bottom-water reservoir.

Hurricane Matthew (2016) and its impact under global warming scenarios

A coupled atmosphere–ocean model was used to study the impact of future ocean warming, both at and below the water surface, on hurricane track and intensity and the associated coastal storm surge and inundation. A strong Saffir–Simpson Category-5 hurricane, Hurricane Matthew made landfall on the South Carolina (SC) coast of the United States (US) in September 2016 and was used as our study case. Future ocean warming was calculated based on the Inter-Governmental Panel on Climate Change (IPCC) RCP 2.6 and RCP 8.5 scenarios. Validated setup of the model was used to simulate the changes in track, intensity, storm surge, and inundation of Hurricane Matthew under future climate ocean warming scenarios. Results showed that the future ocean warming could make the hurricanes stronger in intensity, which, in turn, will greatly increase subsequent coastal storm surge and inundation. For example, under the RCP 8.5 scenario, Matthew’s maximum wind speed would increase by 18 knots (12.97%), its minimum sea-level pressure would deepen by 26 hPa (2.78%), and the coastal area inundated would increase by 70.20% from that of the present day. Moreover, the increases in coastal surge and inundation could likely lead to a downstream blocking of upstream water systems, thereby exacerbating upstream lateral flooding as the rivers go into storage modes; but that potential is beyond the scope of this study.

LATERAL FLOODING ASSOCIATED TO WAVE FLOOD GENERATION ON RIVER SURFACE

Abstract. This research provides a wave flood simulation using a high resolution LiDAR Digital Terrain Model. The simulation is based on the generation of waves of different amplitudes that modify the river level in such a way that water invades the adjacent areas. The proposed algorithm firstly reconstitutes the original river surface of the studied river section and then defines the percentage of water loss when the wave floods move downstream. This procedure was applied to a gently slope area in the lower basin of Coatzacoalcos river, Veracruz (Mexico) defining the successive areas where lateral flooding occurs on its downstream movement.

LATERAL FLOODING ASSOCIATED TO WAVE FLOOD GENERATION ON RIVER SURFACE

This research provides a wave flood simulation using a high resolution LiDAR Digital Terrain Model. The simulation is based on the generation of waves of different amplitudes that modify the river level in such a way that water invades the adjacent areas. The proposed algorithm firstly reconstitutes the original river surface of the studied river section and then defines the percentage of water loss when the wave floods move downstream. This procedure was applied to a gently slope area in the lower basin of Coatzacoalcos river, Veracruz (Mexico) defining the successive areas where lateral flooding occurs on its downstream movement.

Modeling tidal distortion in the Ogeechee Estuary

A 3D numerical model is used to simulate the distortion of tidal hydrodynamics in the Ogeechee Estuary, GA. The Ogeechee, like many estuaries found in the Southeastern US, consists of shallow channel networks and extensive intertidal storage in the form of wetlands. Such features are known to induce non-linear overtide generation and significant tidal distortion, otherwise known as tidal stage asymmetry. Simulations are run with varying parameters to assess their effects on modeling tidal distortion for the Ogeechee Estuary: bottom friction coefficients, enhanced wetland friction coefficients, and tidal flat elevations. To succinctly quantify the degree of distortion across the domain, the statistical parameters of skewness and asymmetry are calculated for time series of water surface heights and channel volume fluxes. The intertidal storage causes the peak flood flux to occur later and the peak ebb flux to occur earlier, thereby resulting in positive asymmetry for the volume flux for the full estuary. However, ebb dominance is a localized feature and varies throughout the estuary. Increasing the intertidal storage by lowering wetland elevation enhances the effects on high tide and volume flux magnitudes, decreasing the ebb-dominance and volume flux asymmetry typically associated with intertidal storage thereby indicating the importance of the wetland elevation over the total storage volume. Increased channel bottom friction reduces ebb-dominance by extending the duration of the falling tide. More interestingly, increased wetland friction reduces the influence of wetland intertidal storage on tidal distortion. The model suggests an increase in wetland friction does little to dampen wave propagation at high tide but rather impedes the lateral flooding of wetlands, reducing ebb dominance. Tidal flat elevation has the largest impact on distortion for the Ogeechee Estuary whereas enhanced wetland and bottom frictional influences on distortion are small, albeit not insignificant.

The effect of lateral flooding on the coolability of irregular core debris beds

The coolability of ex-vessel core debris is an important issue in the severe accident management strategy of, e.g. the Nordic boiling water reactors. In a core melt accident, the molten core material is expected to discharge into the containment and form a porous debris bed on the pedestal floor of a flooded lower drywell. The debris bed generates decay heat which must be removed by boiling in order to stabilize the debris bed and to prevent local dryout and possible re-melting of the material. The STYX test facility which consists of a cylindrical bed of irregular alumina particles has been used to investigate the effect of lateral coolant inflow on the dryout heat flux of the particle bed. The lateral flow was achieved by downcomers attached on the sides of the test rig. The downcomers provide coolant into the lower region of the bed by natural circulation. Both homogenous and stratified bed configurations have been examined. It was observed that the dryout heat flux is increased by 22–25% for the homogenous test bed compared to the case with no lateral flooding. For the stratified configuration with a fine particle layer on top of the bed, no significant increase in the dryout heat flux was observed. The experiments have been analyzed by using the MEWA-2D code. Models which include explicit consideration of gas–liquid friction were used in the calculations in order to realistically capture the lateral flow configuration.

The features of peat-accumulation process at the southern slope of the Great Vasyugan Bog

The peat-forming process of the southern margin of the taiga zone in West Siberia depends on climatic fluctuations, which have an effect on the peat stratigraphy and chemical composition of peat. It is shown that the contemporary warming does not interrupt the bog formation, which is due to the lateral flooding by water came from adjoining peatlands and periodical waterlogging of floodplain depressions during the years of excessive water supply.

The feasibility of reservoir monitoring using time-lapse marine CSEM

Monitoring changes in hydrocarbon reservoir geometry and pore-fluid properties that occur during production is a critical part of estimating extraction efficiency and quantifying remaining reserves. We examine the applicability of the marine controlled-source electromagnetic (CSEM) method to the reservoir-monitoring problem by analyzing representative 2D models. These studies show that CSEM responses exhibit small but measureable changes that are characteristic of reservoir-depletion geometry, with lateral flooding producing a concave-up depletion-anomaly curve and bottom flooding producing a concave-down depletion-anomaly curve. Lateral flooding is also revealed by the spatial-temporal variation of the CSEM anomaly, where the edge of the response anomaly closely tracks the retreating edge of the flooding reservoir. Measureable changes in CSEM responses are observed when 10% of the resistive reservoir is replaced by conductive pore fluids. However, to avoid corrupting the relatively small signal changes associated with depletion, the acquisition geometry must be maintained to a fraction of a percent accuracy. Additional factors, such as unknown nearby seafloor inhomogeneities and variable seawater conductivity, can mask depletion anomalies if not accounted for during repeat monitoring measurements. Although addressing these factors may be challenging using current exploration CSEM practices, straightforward solutions such as permanent monuments for seafloor receivers and transmitters are available and suggest the method could be utilized with present-day technology.

Litter Decomposition Processes in a Floodplain Forest

Litter decomposition processes were studied in a floodplain forest in South Carolina. Annual decomposition of mixed leaf species decreased from 85 % at the streambank to 58 % in the contiguous upland terrace forest. This decrease in weight loss was correlated with reduced flooding and an increase in more resistant litter substrates at the upland terrace. Species-specific studies indicated that sweet gum leaves decomposed more slowly than red maple, black gum and red ash. Sweet gum leaves had higher initial lignin and cellulose concentrations and larger C:N ratios than the other species. Nutrient release rates from litter varied across the floodplain. Magnesium and K leached quite rapidly within the floodplain, whereas Ca and N losses were more gradual. In contrast, Mg and K losses were less and Ca and N immobilization occurred in the more resistant litter on the unflooded upland terrace. The patterns of nutrient release were generally similar for the four floodplain species tested. Decomposition and recycling processes are different on the floodplain and upland terrace forest. Intrasystem nutrient cycling appears tight in the sandy, nutrientpoor upland terrace forest. Mechanisms such as litter burial during flooding and the timing of nutrient mineralization can limit nutrient export from the floodplain forest. INTRODUCTION Considerable ecological interest has been focused on the mechanisms of material exchange between terrestrial and aquatic habitats (Likens and Bormann, 1974). Alluvial stream-swamps in coastal plain areas represent excellent examples of the magnitude and complexity of potential import-export processes. These systems are characterized by low water velocity, extensive lateral flooding and long water-retention times. Allochthonous inputs from vegetation and fluvial transport often occur over a broad area of floodplain where materials are subject to high metabolic processing (Mulholland, 1981) and possible surface drainage losses during the annual hydroperiod. Recent evidence suggests that coastal plain swamps of the Southeastern U.S. may serve as nutrient traps, effectively removing material added through overland flow from the stream channel (Wharton, 1970; Brinson, 1977; Wharton et al., 1982). The role of overland flooding in the redistribution and long-term retention of radioisotopes in coastal plain streams has been clearly documented (Ragsdale and Shure, 1973). In contrast, Mulholland and Kuenzler (1979) and Mulholland (1981) have reported net fluvial exports of organic carbon from North Carolina swamp-draining watersheds. These studies emphasize the need for further examination of the mechanisms that promote the immobilization or loss of materials in alluvial systems and thus govern downstream export from the overall stream corridor. Organic litter is a major component of material exchange in alluvial habitats. Litter entering the stream-swamp corridor may be displaced downstream (Post and de la Cruz, 1977; Peterson and Rolfe, 1982) or be retained within the floodplain and undergo decomposition in situ. Floodplains in southeastern coastal plain systems retain coarse particulate organic matter effectively, although dissolved carbon losses may be high following metabolic processing and leaching from floodplain litter (Mulholland, 1981). Brinson (1977) indicated nutrient cycling may be tight in coastal plain alluvial swamps. Nutrients accumulate in decomposing litter during the nongrowing season when potential flooding losses would be greatest. The extent and timing of flooding can strongly influence decomposition and nutrient release in these alluvial habitats (Brinson, 1977; Brinson et al., 1981). 'Present address: Environmental Protection Division, Georgia Department of Natural Resources, 270 Washington St. SW, Atlanta 30034. 2Present address: Department of Biology, University of Alabama, University 35486.