Basin Characteristics Research Articles

Impact of tectonics on drainage network evolution of Suru basin, Kargil N/w Himalaya, Jammu and Kashmir, India

The main objective of this paper is to work out quantitative measurement of various geomorphic parameters as well as analysis of geomorphic landforms to study the tectonic character of Suru basin. Morphometric analysis, being widely used to assess the drainage characteristics of the river basins, has also been found to be a useful tool to delineate tectonically active zones. A number of parameters including the mountain front sinuosity, asymmetry factor, transverse topography symmetry, hypsometry, longitudinal profile and the shape parameters have been used. The low mountain front sinuosity values < 1.4 indicate that the tectonic forces dominate over erosive activity. Also the asymmetry factor 66.98% suggests that the right side of the basin has experienced uplift with the development of unpaired river terraces. Hypsometric integral 0.96, convex up hypsometric curve and the GPS data of year 2011–2013 indicate that the relief of the basin is high relative to mean, is in youthful stage and actively uplifting at the rate of 2.18 ± 0.99 mm/year. The shape parameters further suggest that the Suru river basin having lower elongation ratio is indicative of elongate shape of basin with tectonic forces outpacing the erosion power. Area-altitude analysis of the Suru river basin indicates that about 72% of the area of the basin is steeply to very steeply sloping and 28% area is moderately to gently sloping. The area-altitude indicates 72% area of basin could slide when there is slight shift in terms of tectonic disturbance. In addition to the geomorphic indices, the field investigations reveal tectonically unstable character, exhibit a complex topography and varied Quaternary sedimentation. The major geomorphic landforms viz., alluvial terraces, alluvial fans, debris cone, scree, and talus cone at the foothills are present throughout the valley with tectonic structures like micro folds, back-tilted beds, deeply incised valleys, faults and tectonic deposits (Ophiolites), indicating that the tectonic activity has affected the basin. The synergized results of geomorphometry, field investigations and GPS data indicate that the Suru basin is tectonically active and uplifting.

Comparing calibration strategies of a conceptual snow hydrology model and their impact on model performance and parameter identifiability

Having a realistic estimation of snow cover by conceptual hydrological models continues to challenge hydrologists. The calibration of the free model parameters is an unavoidable step and the uncertainties resulting from the use of this optimal set remains a source of concern, especially in forecasting applications and climate changes impact assessments. This study seeks to improve the calibration of the conceptual hydrological model GR4J coupled with the Cemaneige snow model, in order to obtain a more realistic simulation of the snow water equivalent (SWE) and to reduce the uncertainty of the free parameters. The performance of the two models was tested over twelve snow-dominated basins in southern Quebec, Canada. Four calibration strategies were adopted and compared. In the first two strategies, the parameters were calibrated against observed streamflow alone using a local and a global algorithm. In the third and fourth strategies the calibration of snow and hydrological parameters was performed against observed streamflow and snow water equivalent (SWE) measured at snow course transects, first separately, and then with a multiobjective approach. An ensemble of equifinal parameters was used to compare the capacity of the global and multiobjective algorithms to improve the parameters identifiability and to assess the impact of parameter equifinality on the temperature sensitivity of spring peak streamflow. The large number of equifinal parameters found during calibration underscores the importance of structural non-identifiability of the coupled GR4J-Cemaneige model. The inclusion of snow observations within a multiobjective calibration improved the simulation of SWE, the identifiability of the parameters and their correlation with basins characteristics. Parameter equifinality caused a small but non negligible uncertainty in the simulated response of spring peak flow to warming temperatures. Parameter equifinality should be considered in climate impact studies in snow-dominated basins where poorly constrained snow parameters can affect the temperature sensitivity of streamflow.

A Review of Earth Observation-Based Analyses for Major River Basins

Regardless of political boundaries, river basins are a functional unit of the Earth’s land surface and provide an abundance of resources for the environment and humans. They supply livelihoods supported by the typical characteristics of large river basins, such as the provision of freshwater, irrigation water, and transport opportunities. At the same time, they are impacted i.e., by human-induced environmental changes, boundary conflicts, and upstream–downstream inequalities. In the framework of water resource management, monitoring of river basins is therefore of high importance, in particular for researchers, stake-holders and decision-makers. However, land surface and surface water properties of many major river basins remain largely unmonitored at basin scale. Several inventories exist, yet consistent spatial databases describing the status of major river basins at global scale are lacking. Here, Earth observation (EO) is a potential source of spatial information providing large-scale data on the status of land surface properties. This review provides a comprehensive overview of existing research articles analyzing major river basins primarily using EO. Furthermore, this review proposes to exploit EO data together with relevant open global-scale geodata to establish a database and to enable consistent spatial analyses and evaluate past and current states of major river basins.

Chronic well leakage probability relative to basin and fluid characteristics.

Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences.

ASSESSMENT OF THE USSURI RIVER FLOOD REGIME CHANGES REGARDING TO CLIMATE PROJECTIONS TO THE END OF THE XXI CENTURY

Detecting reaction of river systems to climate changes is one of the key problems in modern hydrology. Moreover, this is the case of the Far East of Russia, where moisture regime variability is well known. The presented article deals with the assessment results of changes in the flood characteristics of the Ussuri rivers basins under the expected climate changes, linked with global warming. The estimates are based on dynamic–stochastic modeling scheme, in which numerous synthetic precipitation series are input to the hydrological model for searching of all kinds of humidification conditions at the investigated catchments. There was used a regional hydrological Flood Cycle Model of small river basin that focuses on the description of runoff formation processes in the summer–autumn flood period. Climate changes input is based on the integration of the regional stochastic rainfall model and General Circulation Models (GCM) data to the end of XXI century (2071–2100). It is shown that an increase in precipitation sum leads to an unproportional response of the evaluated flood flow characteristics. The relative increase in the mean values of the maximum flow reaches 4–5 times and 2–3 times for the seasonal runoff depth depending on applied GCM and climate scenarios. The obtained results are consistent with the analysis of observational data using the “elasticity coefficient” and previous investigations. Therefore, flood risks could be expected at the investigated territory due to climate changes.

Evaluation of Gene Expression Method for Rainfall-Runoff Relationship: Case study of the E21A057 Station

A reliable model for the prediction of rainfall-runoff process is important for water resource planning and management. The accurate estimation of monthly rainfall and runoff also can be considered a key element for predicting drought in the near future. Rainfall is the most important factor for flow. Therefore, knowing the amount of rainfall in a basin can help to improve the accuracy of forecasting models for river flow Precipitation and flow have a complex and nonlinear relationship. Additionally, the effect of precipitation on the flow depends on basin characteristics such as topography, shape, slope, type of soil, soil moisture, temperature and evaporation. These parameters are generally considered in conceptual models. However, since the basin characteristics are difficult to determine, in recent years the relationship between precipitation and flow can be made with limited data by artificial intelligence methods. In this study, monthly mean flow values of E21A057 Stream Gauging Station (SGS) are estimated by Genexpression Programming (GEP) and Multiple Linear Regression (MLR) methods by using monthly total precipitation values of 17204 meteorological observation station. Models which are prepared using different input parameters, the GEP method is found to be more successful in almost all cases compared to the MLR method. The most successful model among all models is determined as DM04 using four input parameters in GEP method. These parameters are Precipitation (P), 1 month lagged flow rate (Q-1), 1 month lagged precipitation (P-1) and 2 month lagged precipitation (P-2).

Mercury Bioaccumulation in Lacustrine Fish Populations Along a Climatic Gradient in Northern Ontario, Canada

Climate change is predicted to alter many processes in boreal aquatic ecosystems, including mercury (Hg) bioaccumulation in fish. We investigated current patterns in fish Hg across a climatic gradient in northern Ontario, Canada, to assess the possible influence of further climate change. Cohabiting populations of walleye (a piscivore) and white sucker (a benthivore) were sampled from lakes spanning over 9.0° of latitude (45° 24′ N–54° 20′ N). Latitudinal trends were evident in climatic conditions, as well as several other ecosystem characteristics over this range. Muscle total Hg concentration ([THg]) was modelled with respect to climatic variables as well as other physical, chemical, and biological variables, and all models were ranked by Akaike information criterion. Neither long-term mean temperature nor precipitation was a strong predictor of current muscle [THg] in either species across this region. Instead, drainage basin characteristics (for example, mean slope) and lake water chemistry (for example, [DOC], [SO4]) were the strongest predictors, followed by fish biological traits (for example, muscle δ13C). Walleye [THg] was more strongly related to water chemistry, and white sucker [THg] was more strongly related to drainage basin physical characteristics. For both species, muscle [THg] showed unimodal relationships with several predictors (for example, latitude, [SO4], [DOC]), peaking in their mid-ranges. Fish [THg] is not strongly associated with current climatic conditions across northern Ontario but may be influenced by climate change in future through indirect effects on water chemistry and food web structure.

Linking Climate, Basin Morphology and Vegetation Characteristics to Fu’s Parameter in Data Poor Conditions

The prediction of long term water balance components is not a trivial issue, even when empirical Budyko’s type approaches are used, because parameter estimation is often hampered by missing or poor hydrological data. In order to overcome this issue, we provided regression equations that link climate, morphological, and vegetation parameters to Fu’s parameter. Climate is here defined as a specific seasonal pattern of potential evapotranspiration and rain: five climatic scenarios have been considered to mimic different conditions worldwide. A weather generator has been used to create stochastic time series for the related climatic scenario, which in turn has been used as an input to a conceptual hydrological model to obtain long-term water balance components with low computational effort, while preserving fundamental process descriptions. The morphology and vegetation’s role in determining water partitioning process has been epitomized in four parameters of the conceptual model. Numerical simulations explored a large set of basins in the five climates. Results show that climate superimposes partitioning rules for a given basin; morphological and vegetation watershed properties, as conceptualized by model parameters, determine the Fu’s parameter within a given climate. A sensitive analysis confirmed that vegetation has the most influencing role in determining water partitioning rules, followed by soil permeability. Finally, linear regressions relating basin characteristics to Fu’s parameter have been obtained in the five climates and tested in a basin for each case, obtaining encouraging results. The small amount of data required and the very low computational effort of the method make this approach ideal for practitioners and hydrologists involved in annual runoff assessment.

A multi-sensor-based evaluation of the morphometric characteristics of Opa river basin in Southwest Nigeria

ABSTRACT Studies have shown that many river basins in the sub-Saharan Africa are largely unmonitored, partly because they are poorly or totally ungauged. In this study, remote sensing products (Landsat, Advanced Spaceborne Thermal Emission and Reflection Radiometer; ASTER and Shuttle Radar Topography Mission; SRTM) that are freely available in the region were harnessed for the monitoring of Opa river basin in southwestern Nigeria. The remote sensing products were complementarily used with topographical sheets (1:50,000), ground based observation and global positioning systems to determine selected morphometric characteristics as well as changes in landuse/landcover and its impact on peak runoff in the Opa river basin. Results showed that the basin is a 5th order basin whose land area has been subjected to different natural and anthropogenic influences within the study period. Urbanisation is a major factor that threatens the basin with degradation and observed changes, and the threats are expected to become worse if restoration is not considered from some tributaries. The study concluded that commentary use of available remote sensing products in the region will provide an important level of decision support information for management and monitoring of river basins.

Anthropogenic Effects on Hydrogen and Oxygen Isotopes of River Water in Cities.

Stable hydrogen and oxygen isotopes are important indicators for studying water cycles. The isotopes are not only affected by climate, but are also disturbed by human activities. Urban construction has changed the natural attributes and underlying surface characteristics of river basins, thus affecting the isotopic composition of river water. We collected urban river water isotope data from the Global Network for Isotopes in Rivers (GNIR) database and the literature, and collected river water samples from the Naqu basin and Huangshui River basin on the Tibetan Plateau to measure hydrogen and oxygen isotopes. Based on 13 pairs of urban area and non-urban area water samples from these data, the relationship between the isotopic values of river water and the artificial surface area of cities around rivers was analyzed. The results have shown that the hydrogen and oxygen isotope (δD and δ18O) values of river water in urban areas were significantly higher than those in non-urban areas. The isotopic variability of urban and non-urban water was positively correlated with the artificial surface area around the rivers. In addition, based on the analysis of isotope data from 21 rivers, we found that the cumulative effects of cities on hydrogen and oxygen isotopes have led to differences in surface water line equations for cities with different levels of development. The combined effects of climate and human factors were the important reasons for the variation of isotope characteristics in river water in cities. Stable isotopes can not only be used to study the effects of climate on water cycles, but also serve as an important indicator for studying the degree of river development and utilization.

Geo-Spatial Dynamics of Snow Cover and Hydro-Meteorological Parameters of Hunza Basin, HKH Region, Pakistan

Snow cover dynamics play an important role in the hydrological characteristics of Upper Indus Basin (UIB) of Pakistan in terms of seasonal accumulation and depletions. The current study has been carried out to understand the snow cover dynamics, hydrological regime and their inter-relationships. Remote sensing satellite data of Moderate Resolution Imaging Spectro-Radiometer (MODIS) for the period 2000–2016 along with hydro-meteorological parameters was used to study the spatio-temporal changes in snow cover of Hunza basin. Snow cover dynamics were analyzed through temporal analysis of snow cover and its association with hydro-meteorological parameters using Pearson correlation, Principle Component Analysis (PCA) and elevation-based sub zones. The study concluded that 25–40% of the basin area is covered by glacier. Snow covered area may reach up to 90–95% of the basin area due to accumulation of seasonal snow. Hydro-meteorological correlation matrices showed highly significant correlation (R = 0.78) among maximum and minimum temperatures and river runoff while no correlation was observed between river runoff and rainfall (R = –0.03). A highly significant negative correlation was found for River runoff and Hunza mean Snow covered area (R = –0.87). The negative coefficient value shows that river runoff increases with snow cover melting when temperature increases. At sub-altitudinal zones level, river runoff has high negative correlation with snow cover at high altitude zones (Zone 2, 3) (R = –0.84, –0.86) while at lower altitude (Zone 1) there was a moderate correlation (R = –0.6) between snow cover and river runoff. This study reveals that river discharge in Hunza basin is closely associated with its snow cover dynamics. River runoff is associated with basin’s snow melt phenomenon triggered by seasonally increasing temperatures. River discharge increases with active snow melting with start of summer during the months of April and May. Snow melt starts first at lower altitude zones followed by higher elevation zones with higher vertical glacial deposits.

Low streamflow trends at human-impacted and reference basins in the United States

We present a continent-scale exploration of trends in annual 7-day low streamflows at 2482 U.S. Geological Survey streamgages across the conterminous United States over the past 100, 75, and 50 years (1916–2015, 1941–2015 and 1966–2015). We used basin characteristics to identify subsets of study basins representative of reference basins with streamflow relatively free from human effects (n = 259), and predominantly agricultural basins (n = 78), regulated basins (n = 220), and urban basins (n = 121). Trend significance was computed using the Mann-Kendall test considering short- and long-term persistence. Lag-one autocorrelation tests of detrended 7-day low streamflows for all gage classes show that time-series independence is not an appropriate assumption for annual low streamflow data at many basins. Among all study gages, upward trends (wetter conditions) in 7-day low streamflows outnumbered downward trends (drier conditions) approximately 2–1 for the 75- and 100-year trend periods—50-year trends indicated roughly equal numbers of increases and decreases. Increases in 7-day low streamflow were consistently observed for all time periods throughout much of the northeastern quadrant of the conterminous U.S. including western New England and the Mid-Atlantic, the southeastern Great Lakes basin, northern Ohio River basin, and the Upper Mississippi River and eastern Missouri River basins. Decreases in 7-day low streamflow were consistently observed for all time periods at many gages in the southeastern U.S. and in the northwestern U.S. in much of Idaho and northwestern Washington. Overall, we observed greater percentages of statistically significant trends at gages with human-induced influences than at reference gages. Low-flow trends at agricultural gages were regionally consistent with trends at reference gages. Regulated basins had many statistically significant upward trends for all three time periods tested, which may be attributed in part to substantial increases in dam-related storage prior to 1970. Urban gages had the greatest percentage of significant decreases in 7-day low flows compared to all other gage classes even though most urban gages saw upward trends in mean annual flows. Urban gages also had the greatest percentage of significant increases in low flows second only to regulated gages, highlighting that urban development can increase or decrease low streamflows depending on the basin-specific development.

New play discoveries in the South Sumatra Basin, Indonesia-Exploration case study in CNPC Jabung Block

The Jabung block is located in the Jambi depression in the northern part of the South Sumatra Basin. According to the tectonic evolution characteristics and the characteristics of the resource/reservoir/trap, together with the trap structure and the hydrocarbon enrichment characteristics of the South Sumatran Basin, the hydrocarbon play of the basin can be divided into the pre-rift period play, the rift period play and depression period play. The pre-rift period play mainly refers to the basement play. The rift-period play mainly refers to the Lahat play, the Lower Talang Akar play and the Upper Talang Akar play. The depression play mainly refers to the Batu Raja play, the lower Gumai play, the upper Gumai play and Air Benakat play. The main hydrocarbon discoveries in the Jabung block are concentrated in the Lower Talang Akar play and the Upper Talang Akar play in the rift period. In recent years, with the exploration activityies in the Jabung block, some new discoveries in striatigraphical traps have been made in the basement play in pre-rift period and the Batu Raja play and the Gumai play in the depression period.

The study of Yanshanian unconformity tectonic events in Northern Junggar Basin

Based on the background of Yanshanian tectonic activity in the northern Junggar basin, the temporal and spatial distribution characteristics of Yanshanian unconformity events in the northern Junggar basin are systematically studied through interpretation and comparison of outcrop profiles and seismic profiles. The study shows that Yanshanian stratigraphic unconformity in the northern part of Junggar Basin mainly manifests in the angle unconformity between Xishanyao formation and Toutunhe formation, Toutunhe formation and Tugulu group, which indicates that the study area mainly experienced three important periods of unconformity: the end of Xishanyao formation in middle Jurassic, the end of Toutunhe formation and the end of Tugulu group in early Cretaceous. From the analysis of the unconformity structure and its regional distribution characteristics, it can be concluded that the most prominent Yanshanian tectonic unconformity events occurred mainly in the late Jurassic and showed the unconformity distribution characteristics of the weak compression fold deformation under the background of strike-slip uplift.

Assessment of geomorphological and hydrological variations in Bhagirathi River Drainage sub-basin with the help of morphometric studies

ABSTRACTInterpretation of geomorphic features and drainage characteristics of Bhagirathi River sub-basin was carried out with the help of morphometric analysis. Various, areal, linear and relief parameters were calculated to assess drainage basin characteristics quantitatively, determine infiltration and surface runoff behavior control of drainage. The drainage network was analyzed using IRS-PAN satellite data and Survey of India toposheets. Findings show that the Bhagirathi sub-basin from Gaumukh to Chirbas exhibits dendritic to sub-dendritic drainage patterns and is characterized by third-order streams up to Chirbas. Stream segments development in the basin is controlled by local relief and slope. The bifurcation ratio indicate disparity of bifurcation between the different stream orders owing to structural control and circularity ratio indicates sub-elongated shape of basin. This study will be helpful for making soil erosion prevention strategies and its conservation and facilitate the understanding of water retention function in river basins.

Regionalization of average flow: a brief review of the literature

The sustainable management of water resources require planning techniques that are dependent on reliable estimates of water bodies flows data. The knowledge of water availability is essential for decision-making; however, data series are generally limited, insufficient and do not cover all places of interest, making it difficult or impossible to carry out strategic water resource planning. In this way, the temporal and spatial gaps can be filled based on robust methodologies. To fill the gaps in the data, spatial information transfer techniques are used, which are called hydrological regionalization. Thus, this article presents a brief bibliographical review, as well as, different applications of the average flow regionalization methods. This method is an important tool to support decision making in the planning and management of water resources. The results found in the researches related to the applicable methodologies of flow regionalization emphasize that the physical, climatic and hydrological diversities of the river basin characteristics require the adoption of specific methods directed to each unit, since the complexity of the ecosystem interactions makes the procedure difficult.

Differences in Response of Terrestrial Water Storage Components to Precipitation over 168 Global River Basins

AbstractA time lag exists between precipitation P falling and being converted into terrestrial water. The responses of terrestrial water storage (TWS) and its individual components to P over the global scale, which are vital for understanding the interactions and mechanisms between climatic variables and hydrological components, are not well constrained. In this study, relying on land surface models, we isolate five component storage anomalies from TWS anomalies (TWSA) derived from the Gravity Recovery and Climate Experiment mission (GRACE): canopy water storage anomalies (CWSA), surface water storage anomalies (SWSA), snow water equivalent anomalies (SWEA), soil moisture storage anomalies (SMSA), and groundwater storage anomalies (GWSA). The responses of TWSA and of the individual components of TWSA to P are then evaluated over 168 global basins. The lag between TWSA and P is quantified by calculating the correlation coefficients between GRACE-based TWSA and P for different time lags, then identifying the lag (measured in months) corresponding to the maximum correlation coefficient. A multivariate regression model is used to explore the relationship between climatic and basin characteristics and the lag between TWSA and P. Results show that the spatial distribution of TWSA trend presents a similar global pattern to that of P for the period January 2004–December 2013. TWSA is positively related to P over basins but with lags of variable duration. The lags are shorter in the low- and midlatitude basins (1–2 months) than those in the high-latitude basins (6–9 months). The spatial patterns of the maximum correlations and the corresponding lags between individual components of the TWSA and P are consistent with those of the GRACE-based analysis, except for SWEA (3–8 months) and CWSA (0 months). The lags between GWSA, SMSA, and SWSA to P can be arranged as GWSA &amp;gt; SMSA ≥ SWSA. Regression analysis results show that the lags between TWSA and P are related to the mean temperature, mean precipitation, mean latitude, mean longitude, mean elevation, and mean slope.

The “mosco” (Hemiptera: Corixidae and Notonectidae) of Lake Cuitzeo, Mexico: an unusual inland water fishery

Lake Cuitzeo is Mexico’s second-largest lake (~ 425 km2). The West Basin is shallow, seasonally astatic and alkaline, and it contains saltwater; it is in this extreme environment that there are fisheries maintained by local fishermen that are based on non-conventional products. These products include the “mosco” (hemipteran water boatmen and backswimmers: Corixidae and Notonectidae), which has become the most important “non-conventional resource” owing to high catch rates and its contribution to the local economy; its uses include its sale as pet food for songbirds and ornamental fishes. No other commercial fisheries of adult Hemiptera are known worldwide. This study records, for the first time, the species composition of the “mosco”, which was investigated through monthly sampling for twelve months at three sites in the West Basin. Seven species of aquatic Hemiptera were found: 5 species of the family Corixidae [Graptocorixa sp. (Hungerford), Corisella mercenaria (Say), Corisella edulis (Champion), Trichocorixa parvula (Champion) and Krizousacorixa azteca (Jaczewski)], and 2 species of the family Notonectidae [Buenoa scimitra (Bare) and Notonecta irrorata (Uhler)]. The seven species are new records for Lake Cuitzeo. Corixidae were more abundant than Notonectidae, at a ratio that varied from 2.3:1 to 34.2:1. Abundance peaks of up to 339 ind. m−2 were recorded during the cold and dry season, from October/November until January, along with the highest salinity and lowest water temperatures. Graptocorixa sp. was the most abundant and widely distributed species in the West Basin, followed by Krizousacorixa azteca. The characteristics of the West Basin, such as its temporality and elevated salinity and pH, have favored the explosive development of this group, probably because these “extreme” conditions are unfavorable for competitors and predators.

Evaluating precipitation datasets for large-scale distributed hydrological modelling

We are experiencing a proliferation of satellite derived precipitation datasets. Advantages and limitations of their promising application in hydrological modelling application have been broadly investigated. However, most studies have analysed only the performance of one or few datasets, were limited to selected small-scale case studies or used lumped models when investigating large-scale basins.In this study, we compared the performance of 18 different precipitation datasets when used as main forcing in a grid-based distributed hydrological model to assess streamflow in medium to large-scale river basins. These datasets are classified as Uncorrected Satellites (Class 1), Corrected Satellites (Class 2) and Reanalysis – Gauges based datasets (Class 3). To provide a broad-based analysis, 8 large-scale river basins (Amazon, Brahmaputra, Congo, Danube, Godavari, Mississippi, Rhine and Volga) having different sizes, hydrometeorological characteristics, and human influence were selected. The distributed hydrological model was recalibrated for each precipitation dataset individually.We found that there is not a unique best performing precipitation dataset for all basins and that results are very sensitive to the basin characteristics. However, a few datasets persistently outperform the others: SM2RAIN-ASCAT for Class 1, CHIRPS V2.0, MSWEP V2.1, and CMORPH-CRTV1.0 for Class 2, GPCC and WFEDEI GPCC for Class 3. Surprisingly, precipitation datasets showing the highest model accuracy at basin outlets do not show the same high performance in internal locations, supporting the use of distributed modelling approach rather than lumped.

The use of watershed geomorphic data in flash flood susceptibility zoning: a case study of the Karnaphuli and Sangu river basins of Bangladesh

The occurrence of heavy rainfall in the south-eastern hilly region of Bangladesh makes this area highly susceptible to recurrent flash flooding. As the region is the commercial capital of Bangladesh, these flash floods pose a significant threat to the national economy. Predicting this type of flooding is a complex task which requires a detailed understanding of the river basin characteristics. This study evaluated the susceptibility of the region to flash floods emanating from within the Karnaphuli and Sangu river basins. Twenty-two morphometric parameters were used. The occurrence and impact of flash floods within these basins are mainly associated with the volume of runoff, runoff velocity, and the surface infiltration capacity of the various watersheds. Analysis showed that major parts of the basin were susceptible to flash flooding events of a ‘moderate’-to-‘very high’ level of severity. The degree of susceptibility of ten of the watersheds was rated as ‘high’, and one was ‘very high’. The flash flood susceptibility map drawn from the analysis was used at the sub-district level to identify populated areas at risk. More than 80% of the total area of the 16 sub-districts were determined to have a ‘high’-to-‘very-high’-level flood susceptibility. The analysis noted that around 3.4 million people reside in flash flood-prone areas, therefore indicating the potential for loss of life and property. The study identified significant flash flood potential zones within a region of national importance, and exposure of the population to these events. Detailed analysis and display of flash flood susceptibility data at the sub-district level can enable the relevant organizations to improve watershed management practices and, as a consequence, alleviate future flood risk.