Water Inundation Research Articles

Rapid Assessment of Groundwater Salinity and Seawater Intrusion Hazard in the Keep River Floodplain, Northern Territory, Australia

The Australian Government’s White Paper on Developing Northern Australia recognised that expanding the size of the Ord irrigation area in the Kimberley Region, northwest Australia offers the potential to significantly enhance both the profitability and economic resilience of the region. This paper reports on the preliminary results of hydrogeological investigations in the Ord Stage 3 development area, a 14,500 ha area of black soil plains in the Keep River floodplain, Northern Territory. Previous investigations in the Keep River floodplain identified potential for groundwater salinity, soil salinity and seawater intrusion (SWI) hazards. These earlier studies recognised that more comprehensive investigations were required to fully assess the risks of large-scale development of irrigated agriculture on groundwater quality and quantity. The Keep River Salinity Mapping Project has been established to provide baseline data on the groundwater system in the Keep River floodplain including aquifer and aquitard distribution and properties, and potential salinity hazards. Specifically, the main aims of the project are to: (1) map the 3D architecture and hydraulic properties of the soil, sub-soils and underlying paleovalley system; (2) map the SWI interface and variations in groundwater salinity; (3) identify potential surface water inundation risks; (4) identify groundwater-dependent ecosystems; and (5) carry out a hydrogeological assessment. Investigations include a programme of airborne electromagnetics (AEM), ground geophysics (ground magnetic resonance (GMR), passive seismic and microgravity), drilling and borehole geophysics, hydrogeological and hydrochemical investigations, and regional soils, geological and morphotectonic mapping. Products generated in this project will be used to parameterise a numerical groundwater model.

Effects of subsurface soil characteristics on wetland–groundwater interaction in the coastal plain of the Chesapeake Bay watershed

AbstractEcosystem services provided by depressional wetlands on the coastal plain of the Chesapeake Bay watershed (CBW) have been widely recognized and studied. However, wetland–groundwater interactions remain largely unknown in the CBW. The objective of this study was to examine the vertical interactions of depressional wetlands and groundwater with respect to different subsurface soil characteristics. This study examined two depressional wetlands with a low‐permeability and high‐permeability soil layer on the coastal plain of the CBW. The surface water level (SWL) and groundwater level (GWL) were monitored over 1 year from a well and piezometer at each site, respectively, and those data were used to examine the impacts of subsurface soil characteristics on wetland–groundwater interactions. A large difference between the SWL and GWL was observed at the wetland with a low‐permeability soil layer, although there was strong similarity between the SWL and GWL at the wetland with a high‐permeability soil layer. Our observations also identified a strong vertical hydraulic gradient between the SWL and GWL at the wetland with a high‐permeability soil layer relative to one with a low‐permeability soil layer. The hydroperiod (i.e., the total time of surface water inundation or saturation) of the wetland with a low‐permeability soil layer appeared to rely on groundwater less than the wetland with a high‐permeability soil layer. The findings showed that vertical wetland–groundwater interactions varied with subsurface soil characteristics on the coastal plain of the CBW. Therefore, subsurface soil characteristics should be carefully considered to anticipate the hydrologic behavior of wetlands in this region.

POST PROCESSING AND ANALYSIS OF STORM SURGE: A CASE STUDY OF HUDHUD AND PHAILIN CYCLONES

Abstract. Tropical cyclones affect the east coast of India due to its distinctive topography which is formed with a network of estuaries, bays, rivers, and inlets that causes inland flooding. The inland inundation of sea water is inflicting severe damage to the life and property. The ocean water entering the beachfront zone results to storm surges. In order to mitigate these storm surges, real-time monitoring and warnings are essential. For better visualization and analyzing the outputs from storm surge models, efficient post-processing tools are required. Hence post-processing of storm surge using GIS is carried out for taking protective measures. Storm surge vulnerable locations along the east coast of India have been identified in perspective of the number of storm surge events. Blue Kenue and SMS softwares are used to generate the unstructured triangular mesh over the study domain. Cyclones Phailin and Hudhud are selected in the current study and the associated surge heights and inundation extents are examined.

The Feasibility of Cooperation to Comply with Land Use Change Obligations in the Marosszög Area of South Hungary

Abstract In many years excess water inundations generate a major obstacle to farming in the lowland part of Hungary, including the Marosszög area. Diverting water to large distances requires an infrastructure that is costly to develop and maintain. Alternatively, low-lying local land segments could be withdrawn from cultivation and utilized to collect the surplus water. The Ecological Focus Area (EFA) requirement of the EU points to the same direction: it requires that 5% of arable land is converted to other, ecologically more beneficial uses. During the research project it was tested if it is feasible to apply a novel economic policy instrument, an auction to trade land use change obligations, to achieve the EFA requirement in a cost effective way through the cooperation of farmers, while also creating a practical solution to manage the seasonal surplus water cover on land. The research was carried out in an interdisciplinary way: a dynamically coupled fully integrated hydrological model, including surface and subsurface modules, was applied by engineers to better understand the interconnections of land use, local hydrology and the role of the water diversion infrastructure; while a pilot auction exercise was conducted by economists with the participation of farmers to understand if cost reductions can be achieved through cooperation, as opposed to individual fulfilment of EFA obligations. The analysis also revealed which segments of the water diversion network are economic to maintain. It was confirmed that it is possible to improve local water management and satisfy the EFA requirements at a reduced cost if appropriate economic incentives are applied to trigger the cooperation of farmers.

Linking geomorphological and demographic movements: The case of Southern Albania

Albania has experienced one of the Europe's highest population migration rates in recent decades. At the same time, the landscape of this country has very dynamic geomorphological behaviour (erosion and ground subsidence), as an effect of various drivers. This paper examines the correlation between the population migrations and geomorphological dynamics in the wider Vlora area in Southern Albania between 1979 and 2016. In social studies and the humanities this interplay is largely unrepresented, whereas in the environmental sciences these two issues have been conceptualized as having a causal relationship. The article develops a tripartite analytic-synthetic model consisting of (A) remote sensing analysis based on automated land/water detection from satellite data; (B) demographic analysis focusing on population changes using the methods of statistical analysis; and (C) extensive anthropological fieldwork grounded on participant observation, archival work and gathering previously inaccessible statistical and other relevant data. The results of this study show that the coastal erosion or water inundation along with other geomorphological (site-specific relief, place-bound ground subsidence and water bodies distribution) and geotectonic characteristics of the wider Vlora area are inextricably bound up with the population migrations. The paper foregrounds new methodological approaches that correlate coastal or peri-coastal erosion with geomorphological, geotectonic and population movements, and provides a holistic framework that can be applied to examine this issue in similar areas elsewhere.

Not a cape, but a life preserver

Interactive sea level rise viewers (ISLRVs) are an increasingly popular risk communication technology designed to help users visualize the effects of water inundation on their region so as to facilitate more prudent decision-making. Designed by and for a variety of stakeholders, these viewers generally have as their goal affording users a more "localized" experience with climate change and sea level rise data, allowing users to explore as specific as street-level the effects of rising waters in coastal regions. While the rise of these tools mirrors the trend in risk communication scholarship towards more localized messaging, there is still more work to be done in terms of providing a more localized user experience for a broader public audience. This article presents the results of a user experience study conducted with 12 residents of a coastal region, the results of which formulate an attempt to develop more insight into techniques for designer localization. The article concludes with concrete recommendations for scholars and practitioners concerned with designing more effective interactive risk communication technologies that respond to the public need for localized information for decision-making.

Application of Remote Sensing in Monitoring Unsustainable Wetlands: Case Study Hamun Wetland

Monitoring wetland as one of the important parts of the global ecosystem is necessary for conservational programs. But, usually, collecting in situ data is restricted in these areas because of their remote locations, vast area and dynamic conditions. Remote sensing provides a cost effective tool to investigate hydrological patterns and the seasonal trend of changes in wetlands. In this paper, Land-use/land-cover change during water inundation period of Hamun wetland was investigated in order to determine change trend during this period. Hamun wetland is an unsustainable ecosystem, and monitoring this wetland is essential for conservation goals. This trend is critical for decision makers in order to plan the conservational scheme in all unsustainable ecosystems. To reach this objective, the land-use/land-cover maps during inundation period of Hamun were produced using Landsat 8 time series images. The results of accuracy assessment showed the classification of water and vegetation have the highest accuracy (94% and 93%, respectively). And the accuracy of plants in the water classes was the lowest (water–veg = 89.9%, veg–water 1 = 88.8%, veg–water 2 = 87.6%). This means the higher misclassification is in determining the vegetation in the water. Then, the changes in the land-cover classes in relation to wetland inundation were investigated. Results of land-use/land-cover change illustrate the regions that were suitable for water birds but lost their suitability when the wetland dried out. These areas are crucial for water bird’s conservation. Satellite data determined these areas with acceptable accuracy.

Assessing the underwater survival of two tick species, Amblyomma americanum and Amblyomma maculatum

The hard (ixodid) ticks Amblyomma americanum and Amblyomma maculatum are found throughout the southeastern United States. To study the effects of water inundation, which is an increasingly common phenomenon in many coastal areas, unfed adult A. americanum and A. maculatum ticks were tested for survival by submergence in three water conditions: freshwater, brackish water, and saltwater. The results demonstrated a significant difference in survival between the two species in all three water conditions, with A. maculatum ticks surviving a shorter time underwater than A. americanum ticks. There is also a significant difference in A. americanum survival among the different water conditions, with the highest mortality in saltwater and the lowest in freshwater. Amblyomma americanum ticks survived the longest in freshwater (70 d), followed by brackish water (64 d), and the shortest survival was in saltwater (46 d), while the longest any A. maculatum tick survived was 24 d in freshwater. These findings demonstrate that any short-term flooding events, e.g., less than a week, would not likely eliminate these species of ticks in the flooded area.

Wetting-induced collapse behavior of kaolinite: influence of fabric and inundation pressure

Collapsible soils are known to withstand high normal stresses without undergoing a significant volume change in an air-dry state. The soil is, however, susceptible to a large volume change upon wetting. The volumetric collapse behavior of these soils is of great engineering interest to address the problem of ground subsidence. Kaolinite was found to be a collapsible soil similar to the loess soil. The collapse mechanism in kaolinite was due to changes in particle association (fabric) with the interaction with different pore fluids. Several physicochemical parameters strongly influenced the particle association by altering the charges on the particle surfaces and edges. The collapse nature of the kaolinite was investigated with great detail in this work. Wetting-induced collapse behavior of kaolinite was studied under the influence of pore-fluid chemistry using a multi-scale approach. The influence of pH, salt concentration, and dielectric pore-fluid environment on the clay behavior was analyzed using sedimentation and collapse tests. The collapse test results were well corroborated with the sedimentation test data, scanning electron microscopy images of lyophilized specimens, and edge isoelectric point (IEPedge). The influence of inundation fluid and inundation pressure on the fabric changes and collapse potential was elucidated. The collapse potential was found to depend on the inundation pressure and pore-fluid characteristics. Maximum collapse potential was observed to be due to water inundation and minimum due to inundation with kerosene. The mechanical pressure at higher inundation pressures helped to bring the clay platelets into better face–face association during the inundation.

Carbon stocks, sequestration, and emissions of wetlands in south eastern Australia.

Nontidal wetlands are estimated to contribute significantly to the soil carbon pool across the globe. However, our understanding of the occurrence and variability of carbon storage between wetland types and across regions represents a major impediment to the ability of nations to include wetlands in greenhouse gas inventories and carbon offset initiatives. We performed a large-scale survey of nontidal wetland soil carbon stocks and accretion rates from the state of Victoria in south-eastern Australia-a region spanning 237,000km2 and containing >35,000 temperate, alpine, and semi-arid wetlands. From an analysis of >1,600 samples across 103 wetlands, we found that alpine wetlands had the highest carbon stocks (290±180 Mg Corg ha-1 ), while permanent open freshwater wetlands and saline wetlands had the lowest carbon stocks (110±120 and 60±50 Mg Corg ha-1 , respectively). Permanent open freshwater sites sequestered on average three times more carbon per year over the last century than shallow freshwater marshes (2.50±0.44 and 0.79±0.45 Mg Corg ha-1 year-1 , respectively). Using this data, we estimate that wetlands in Victoria have a soil carbon stock in the upper 1m of 68 million tons of Corg , with an annual soil carbon sequestration rate of 3 million tons of CO2 eq. year-1 -equivalent to the annual emissions of about 3% of the state's population. Since European settlement (~1834), drainage and loss of 260,530ha of wetlands may have released between 20 and 75 million tons CO2 equivalents (based on 27%-90% of soil carbon converted to CO2 ). Overall, we show that despite substantial spatial variability within wetland types, some wetland types differ in their carbon stocks and sequestration rates. The duration of water inundation, plant community composition, and allochthonous carbon inputs likely play an important role in influencing variation in carbon storage.

Comparing Landsat and RADARSAT for Current and Historical Dynamic Flood Mapping

Mapping the historical occurrence of flood water in time and space provides information that can be used to help mitigate damage from future flood events. In Canada, flood mapping has been performed mainly from RADARSAT imagery in near real-time to enhance situational awareness during an emergency, and more recently from Landsat to examine historical surface water dynamics from the mid-1980s to present. Here, we seek to integrate the two data sources for both operational and historical flood mapping. A main challenge of a multi-sensor approach is ensuring consistency between surface water mapped from sensors that fundamentally interact with the target differently, particularly in areas of flooded vegetation. In addition, automation of workflows that previously relied on manual interpretation is increasingly needed due to large data volumes contained within satellite image archives. Despite differences between data received from both sensors, common approaches to surface water and flooded vegetation mapping including multi-channel classification and region growing can be applied with sensor-specific adaptations for each. Historical open water maps from 202 Landsat scenes spanning the years 1985–2016 generated previously were enhanced to improve flooded vegetation mapping along the Saint John River in New Brunswick, Canada. Open water and flooded vegetation maps were created over the same region from 181 RADARSAT 1 and 2 scenes acquired between 2003–2016. Comparisons of maps from different sensors and hydrometric data were performed to examine consistency and robustness of products derived from different sensors. Simulations reveal that the methodology used to map open water from dual-pol RADARSAT 2 is insensitive to up to about 20% training error. Landsat depicts open water inundation well, while flooded vegetation can be reliably mapped in leaf-off conditions. RADARSAT mapped approximately 8% less open water area than Landsat and 0.5% more flooded vegetation, while the combined area of open water and flooded vegetation agreed to within 0.2% between sensors. Derived historical products depicting inundation frequency and trends were also generated from each sensor’s time-series of surface water maps and compared.

Floodplain plant productivity is better predicted by particulate nutrients than by dissolved nutrients in floodwater

When rivers flood, nutrients exchange between the river and the floodplain, enhancing floodplain vegetation productivity, as described by the flood pulse concept. However, river water may not reach the edge of the floodplain if there are other sources of inundation water. Also, particulate nutrients travel less far from the river than dissolved nutrients and are more likely to remain available to vegetation during the growing season. This would mean that high nutrient input by river water, and associated high floodplain plant productivity, likely occurs only in the vicinity of the river channel. This paper tests 3 hypotheses derived from these observations related to the validity of the Flood Pulse concept and the relation between floodplain plant productivity and dissolved resp. particulate nutrients.We mapped particulate nutrient and dissolved nutrient concentrations in floodplain inundation water across the Biebrza floodplain (Poland), and assessed their spatial relationships with topographical parameters, aboveground biomass and species richness. Particulate nitrogen (N) and phosphorus (P) deposition and dissolved N decreased significantly with distance from the river and with elevation, and increased significantly with water depth. Dissolved P was not significantly correlated with topographical parameters or water depth. Aboveground biomass correlated significantly with particulate N and P deposition, but not with dissolved N or P.We conclude the edge of inundation is a poor predictor of the zone of high productivity. Nutrient input is higher near the river channel due to deposition of particulate nutrients, which are thus more relevant for vegetation productivity than dissolved nutrients. Spatial particulate nutrient patterns should therefore be integrated in monitoring programmes for policy and research. We further recommend refining the flood pulse concept to take into account the spatial deposition of river derived particulate nutrients, as well as non river-derived inundation water sources.

Small-Scale Pullout Test of a Geogrid-Reinforced Unsaturated Soil with Suction Monitoring

Abstract The use of local fine-grained soils in geosynthetic-reinforced structures can significantly reduce costs when granular materials are difficult to access. Another beneficial aspect of these soils is that enhanced mechanical behavior is expected with fine-grained soils under unsaturated conditions. With structures built in unsaturated conditions, stability analyses based on unsaturated soil mechanics would properly characterize and accurately predict the structural behavior with fine-grained soils. Accordingly, the interface shear strength between fine-grained soils and geosynthetics should also be assessed by unsaturated pullout or direct shear testing. In this article, the effect of matric suction on the pullout behavior of a polyester geogrid embedded in a fine-grained soil was evaluated using a small-scale testing apparatus. A miniature tensiometer located in the proximity of the soil-geogrid interface enabled monitoring of the matric suction of soil during pullout to evaluate its effect on the interface shear strength. A design approach for prediction of unsaturated interface strength is also assessed in this study. Three typical values of matric suction were identified during pullout: initial, peak, and residual. In the case of interfaces under water inundation, the pore water pressures developed and increased with the increase of overburden pressures. For drier interfaces, matric suction increases with increases of overburden pressure. Significant reductions (60 %) in peak pullout forces were observed for minor increases in soil moisture contents. Analyses using the moisture reduction factor indicated up to a 70 % loss of soil-geogrid interface shear strength as a result of wetting. The increase in unsaturated soil-geogrid interface strength due to the reduction of moisture content was attributed more to adhesion than to friction for the fine-grained soil used in this research. The analytical approach proposed in this study to predict the pullout strength of unsaturated interfaces has been demonstrated to be quite consistent with the actual strength values assessed from the small-scale pullout tests, primarily for higher values of overburden pressures. Matric suction values obtained from the soil-water retention curve were shown to be reliable parameters for use in the proposed analytical approach for prediction of the pullout strength of unsaturated soil-geosynthetic interfaces.

Assessing global surface water inundation dynamics using combined satellite information from SMAP, AMSR2 and Landsat

A method to assess global land surface water (fw) inundation dynamics was developed by exploiting the enhanced fw sensitivity of L-band (1.4 GHz) passive microwave observations from the Soil Moisture Active Passive (SMAP) mission. The L-band fw (fwLBand) retrievals were derived using SMAP H-polarization brightness temperature (Tb) observations and predefined L-band reference microwave emissivities for water and land endmembers. Potential soil moisture and vegetation contributions to the microwave signal were represented from overlapping higher frequency Tb observations from AMSR2. The resulting fwLBand global record has high temporal sampling (1–3 days) and 36-km spatial resolution. The fwLBand annual averages corresponded favorably (R = 0.85, p-value < 0.001) with a 250-m resolution static global water map (MOD44W) aggregated at the same spatial scale, while capturing significant inundation variations worldwide. The monthly fwLBand averages also showed seasonal inundation changes consistent with river discharge records within six major US river basins. An uncertainty analysis indicated generally reliable fwLBand performance for major land cover areas and under low to moderate vegetation cover, but with lower accuracy for detecting water bodies covered by dense vegetation. Finer resolution (30-m) fwLBand results were obtained for three sub-regions in North America using an empirical downscaling approach and ancillary global Water Occurrence Dataset (WOD) derived from the historical Landsat record. The resulting 30-m fwLBand retrievals showed favorable spatial accuracy for water (commission error 31.46%, omission error 30.20%) and land (commission error 0.87%, omission error 0.96%) classifications and seasonal wet and dry periods when compared to independent water maps derived from Landsat-8 imagery. The new fwLBand algorithms and continuing SMAP and AMSR2 operations provide for near real-time, multi-scale monitoring of global surface water inundation dynamics and potential flood risk.

Long-term surface water changes and driving cause in Xiong’an, China: from dense Landsat time series images and synthetic analysis

China’s government statement recently reported the plan of constructing Xiong’an New Area, which aims to phase out some extra capital functions from Beijing and to explore an innovative urban development mode with the priority in eco-environmental protection. The New Area is located in the semi-arid North China Plain (NCP) and is home to NCP’s largest natural freshwater wetland, Baiyangdian Lake. A comprehensive realization of surface water dynamics would be crucial for policy-makers to outline a sustainable environment development strategy for New Area. In this study, we used a total of 245 time slices of cloud-free Landsat images to document the continuous changes of water bodies within Xiong’an City during 1984–2016 and to provide detailed evidence of water presence and persistency states and changes under the influences of climate change and human actions. Our results reveal that the New Area water body areas varied dramatically during the past 33 years, ranging from 0.44 km2 in April 1988 to 317.85 km2 in February 1989. The change of surface water area was not characterized by a monotonically decreasing tendency. The evolution processes can be divided into four sub-stages: the first extreme desiccation in mid-1980s, the wet stage with the most extensive inundation areas and strong inter-annual fluctuations from late-1988 to late 1999, another desiccation stage in early 2000s, and the overall recovering stage between 2007 and 2016. We also mapped the maximum water inundation extents and frequencies of all-season, pre-wet season (February-May) and post-wet season (September-December) for the 33 years and different sub-periods. Although there is good agreement between time series of surface water area evolution in the New Area and station-based precipitation and evaporation variations, multiple lines of evidences reviewed in previous research indicate that the degraded Baiyangdian Lake was also tightly associated with human activities from various aspects, including dam construction, groundwater extraction, agricultural irrigation, etc. We highlighted the current status of exploring the driving mechanism of surface water changes and existing problems, and then offer recommendations.

An Integrated Scenario Ensemble-Based Framework for Hurricane Evacuation Modeling: Part 2-Hazard Modeling.

Hurricane track and intensity can change rapidly in unexpected ways, thus making predictions of hurricanes and related hazards uncertain. This inherent uncertainty often translates into suboptimal decision-making outcomes, such as unnecessary evacuation. Representing this uncertainty is thus critical in evacuation planning and related activities. We describe a physics-based hazard modeling approach that (1) dynamically accounts for the physical interactions among hazard components and (2) captures hurricane evolution uncertainty using an ensemble method. This loosely coupled model system provides a framework for probabilistic water inundation and wind speed levels for a new, risk-based approach to evacuation modeling, described in a companion article in this issue. It combines the Weather Research and Forecasting (WRF) meteorological model, the Coupled Routing and Excess STorage (CREST) hydrologic model, and the ADvanced CIRCulation (ADCIRC) storm surge, tide, and wind-wave model to compute inundation levels and wind speeds for an ensemble of hurricane predictions. Perturbations to WRF's initial and boundary conditions and different model physics/parameterizations generate an ensemble of storm solutions, which are then used to drive the coupled hydrologic + hydrodynamic models. Hurricane Isabel (2003) is used as a case study to illustrate the ensemble-based approach. The inundation, river runoff, and wind hazard results are strongly dependent on the accuracy of the mesoscale meteorological simulations, which improves with decreasing lead time to hurricane landfall. The ensemble envelope brackets the observed behavior while providing "best-case" and "worst-case" scenarios for the subsequent risk-based evacuation model.

Coastal saline Soils of India: A review

Coastal region covers a long strip along the east coast (West Bengal, Orissa, Andhra Pradesh, Pondicherry and Tamil Nadu) and west coast (Gujarat, Maharashtra, Karnataka and Kerala). Salinity is mainly due to the presence of saline ground water at shallow depth and frequent sea water inundation in the low lying areas. Sea water intrusion into the aquifers may be direct, but also range of complex geochemical processes like, inter-aquifer mixing, mobilization of brines, water-rock interaction and anthropogenic contamination. NaCl and Na2SO4 are the dominant salts, with abundance of soluble cations in the order of Na&gt;Mg&gt;Ca&gt;K. The salt reaches the soil surface through capillary rise during dry season and makes the soil saline and unproductive for agriculture. Salinity ranges 0.5 dSm-1 in monsoon and 50 dSm-1 in summer. Proper understanding about the nature, properties and prevailing constraints related to diverse group of coastal soils is necessary to undertake better management practices to improve the productivity and quality of such low productive salty soils.

Spectral matching based on discrete particle swarm optimization: A new method for terrestrial water body extraction using multi-temporal Landsat 8 images

Terrestrial water, an important indicator of inland hydrological status, is sensitive to land use cover change, natural disaster and climate change. An accurate and robust water extraction method can determine the surface water distribution. In this paper, a new method, called the spectrum matching based on discrete particle swarm optimization (SMDPSO) is proposed to recognize water and nonwater in Landsat 8 Operational Land Imager (OLI) images. Only two parameters, the standard water spectrum and the tile size, are considered. These parameters are sufficiently stable so it is unnecessary to change their values for different conditions. By contrast, in supervised methods, samples are chosen based on conditions. Eight test sites covering various water types in different climate conditions are used to assess the performance relative to that of unsupervised and supervised methods in terms of overall accuracy (OA), kappa coefficients (KC), commission error (CE) and omission error (OE). The results show that: (1) SMDPSO achieves the highest accuracy and robustness; (2) SMDPSO has lower OE but higher CE than the supervised method, which means that SMDPSO is the least likely to misclassify water as nonwater, but is more likely to misclassify nonwater as water; (3) SMDPSO has advantages with respect to removing shallows and dark vegetation and preserving the real distribution of small ponds, but cannot recognize shadows, ice, or clouds without the help of other data such as DEM. In addition, a case of flooding in northeastern China is analyzed to demonstrate the applicability of SMDPSO in water inundation mapping. The findings of this study demonstrate a novel robust, low-cost water extraction method that satisfies the requirements of terrestrial water inundation mapping and management.

Combined effect of water inundation and heavy metals on the photosynthesis and physiology of Spartina alterniflora

The frequency and duration of tidal flooding significantly influence the bioavailability of heavy metals (HMs) in sediment and hence exert toxicological effects on coastal wetland plants. In this study, the combined effects of different water inundation times (3, 6, 9, and 12 h) and HMs (Cu, Zn, Pb, and Cr) on the photosynthesis and physiology of Spartina alterniflora were investigated under greenhouse conditions. Results showed that S. alterniflora was somehow tolerant to the combined HMs treatments, and only the highest level of HM treatment decreased leaf chlorophyll content. Furthermore, the plants did not show any signs of victimization. Different times of water inundation with HMs did not exert any significant effect on the malonaldehyde (MDA) and chlorophyll contents in the leaves of S. alterniflora at day 20. Prolonged water inundation time at day 60 significantly reduced leaf chlorophyll content with the decrease in leaf photosynthetic rate, which was accompanied by a significant increase in the intercellular concentration of CO2. At day 60, abscisic acid dose-dependently increased along the different water inundation times, indicating that this phytohormone is involved in plant responses to flooding stress. Peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), showed different responses to the combined treatment of water inundation and HMs at different times. At day 20, the long duration of water inundation and HMs treatments (9 h+HMs and/or 12 h+HMs) significantly increased enzyme activity in the leaves compared with the control group (6 h). At day 60, the POD and SOD activities in the leaves of S. alterniflora decreased with prolonged water inundation time, and root APX activity significantly decreased compared with the 6 h water inundation treatment.

Buffering capacity of paddy field as the reservoir of rainwater and surface runoff in the Lowokwaru subdistrict, Malang, East Java

Paddy fields produce ecological services that improve environmental quality in urban areas, one of them was flood control through retaining rainwater and surface runoff within the embankment of paddy field. The ability to retain water is known as the buffering capacity (BC), which is the function of soil moisture, embankment height, water inundation and rice-plant interception during the growing periode. The intermitten system of water inundation applied by farmers resulted in changes of the BC on daily basis. The calculation of BC was divided into five categories for accuracy, which were : (1) BC during the Harvest; (2) BC with inundation at vegetative and generative phase (VGG); (3) BC with inundation during Land Preparation and Planting phase (OTTG); (4) BC without inundation during the vegetative and generative phase (VGTG); and (5) BC without inundation during the land preparation and planting phase (OTTTG). The purpose of this research was to measure potential buffering capacity of paddy field in Lowokwaru Subdistrict and to estimate amount of rainwater and surface runoff which could be accommodated within the buffering capacity. The average of daily BC in seven different villages were 1,650.81– 3,961.81 m 3 /ha and the total BC for 241 paddy field was about 823,156.36 m 3 . It was only a small percentage of average daily BC filled by rainwater (14.07-33.31%) and left the rest to be filled by surface runoff water. The paddy field of 241 ha in Lowokwaru Subdistrictis was capable to receive surface runoff from surrounding areas up to 1,698.66 ha.