Catchment Response Research Articles

An evaluation of high frequency turbidity as a proxy for riverine total phosphorus concentrations

Surface water eutrophication resulting from excessive phosphorus (P) inputs is one of today's most challenging environmental issues. Riverine total phosphorus (TP) concentrations have high temporal variability, which complicates flux estimation. We evaluated the usefulness of high frequency in-situ turbidity measurements as a proxy for TP in Sävjaån, a river draining a mixed land use catchment (722 km2) in central Sweden. Turbidity was monitored every 10th–15th minute during 6 consecutive years (2012–2017). Linear regression showed a good relationship between high frequency turbidity and TP (r2 = 0.64) and could hence be used for comparison of flux estimation methods. Predictive power of the turbidity-TP relationship was not improved by adding seasons, hydrograph rising/falling limb or high/low stream discharge to the model which argues for a single transfer function relating turbidity and TP. Both TP and turbidity were log-normally distributed. However, flux estimates were sensitive to data transformation; predicted TP concentrations and fluxes based on log-transformed data were biased towards lower concentrations and fluxes compared to non-transformed data. In five of six years grab sample and high frequency estimated TP fluxes were similar (grab sample estimates −10% to +13% P transport compared to high frequency flux estimates). The exception was in 2013, when a 50-year spring flood occurred, and the grab sample estimated flux was 56% larger than that estimated from high frequency data. Thus, the flux comparisons were mostly affected by stream discharge, which underlines the importance of capturing high discharge episodes with, e.g. in situ sensors. While uncertainties regarding the use of turbidity as a proxy for TP remain, it is clear that credible water chemistry data can be obtained with current high frequency sensors. We conclude that high frequency data can be used to better understand catchment response to external pressures and gain insights into water quality that will be missed with grab sampling.

Geology controls streamflow dynamics

Relating stream dynamics to catchment properties is essential to anticipate the influence of changing environmental conditions and to predict flows of ungauged rivers. Although the importance of subsurface processes in catchment hydrology is widely acknowledged, geological characteristics are rarely explicitly included in studies assessing physiographic controls on catchment dynamics. In this investigation of 22 catchments of the Swiss Plateau and Prealpes, we use a simple linear regression approach to analyze the relationship between streamflow indicators and various geological and hydrogeological properties of the bedrock and quaternary deposits, along with meteorological, soil, land use and topographical characteristics. We use long-term discharge percentiles, as well as dimensionless flow duration curves (FDC, standardized by long-term mean discharge) that allow to evaluate the catchment response to climate forcing. While climate conditions dominate the high to medium discharge percentiles (Q5–Q50), the capacity of the catchments to buffer the meteorological forcing can only be attributed to geological characteristics. The sandstone proportion in the catchments explains 54% of the variance of both extremities of the dimensionless FDC (Q5/Qmean and Q95/Qmean) and productive quaternary deposits are responsible of 55% resp. 58% of the variance of the two ratios. Examining the hydrogeological characteristics of both bedrock and quaternary lithologies considerably improves the understanding of catchment dynamics.

Land Use‐Dependent Preferential Flow Paths Affect Hydrological Response of Steep Tropical Lowland Catchments With Saprolitic Soils

AbstractForested catchments in Central Panama can produce more base flow during the dry season compared to pasture catchments—the so‐called “forest sponge effect.” During rainfall events, peak storm runoff rates and storm runoff coefficients can be lower for forested catchments than pasture catchments, even when they have similar topographic characteristics, underlying geology, and soil texture. The internal mechanism of these differences in hydrological response due to land use is yet to be fully understood. A distributed model explicitly simulating preferential flow paths (PFPs), which is referred to as “PFPMod,” is used to explain the hydrological response caused by land use using data from three catchments with distinct land covers in Central Panama. Input parameters of forest and pasture land covers were identified using field observations and literature values. Multiple satisfactory objective criteria demonstrate that the two end‐member land cover parameter sets are adequate to explain the observed difference in dry‐season base flow and storm runoff coefficients. Field measurements of matrix infiltrability using soil cores and plot‐scale infiltration capacity enabled estimating the number of vertical macropores that fully penetrate the root zone. Model simulation results demonstrate that fast drainage through lateral PFPs in the early wet season and high flow in vertical PFPs to recharge deep groundwater in the late wet season contribute to the observed differences in peak storm runoff and the “forest sponge effect” during the dry season. This study provided insights to the mechanism by which reforestation may help to restore ecosystem services and water security in tropical settings.

Runoff, flood peaks and proportional response in a combined nested and paired forest plantation/peat grassland catchment

In an unusual combined nested and paired catchment experiment in northern England, the 1.5-km2 Coalburn catchment (90% mature plantation forest with a dense drainage ditch network) is paired with the 1.4-km2 Flothers catchment (64% peat grassland), both being nested within the 6.9-km2 Throssburn mixed forest and peat grassland catchment. In only the second such UK quantification, a 100% forest cover reduces annual runoff relative to a 100% grassland cover by 24%. The study provides rare field (as opposed to model) evidence showing that the impact of land use on flood peaks is moderated by catchment saturation and by extreme rainfall. Flood frequency curves differ according to land use at the smaller return periods but the data are not sufficient to confirm that the pattern extends to the highest floods. Against conventional expectation, flood peaks tend to be larger and flashier in the forest catchment, apparently the consequence of the forest ditching. Springtime monthly runoff/rainfall ratios in the peat grassland catchment may reach 100%, representing a seasonal sponge effect which is eliminated from the forest catchment through the effects of the ditches. Combination of the paired and nested catchments provides a highly unusual opportunity to show that, at the annual scale, the integrated catchment response can be obtained by combining the responses of the separate land covers according to the proportions of the catchment that they occupy, an assumption widely made but rarely, if ever, tested.

Extending the Rational Method for assessing and developing sustainable urban drainage systems

Onsite runoff control is considered an important part of sustainable urban drainage schemes, but estimating the maximum runoff flow rate from a catchment with onsite runoff controls remains controversial. Runoff controls complicate the issue by dividing the catchment into several subcatchments that feed into individual runoff controls, which dynamically regulate the catchment imperviousness. Rational Method (RM) is the most-employed technique to determine maximum flow rates for designing urban drainage infrastructures, but it cannot handle such conditions. Nonetheless, it has advantages over alternative methods in terms of principle from the urban drainage design perspective. This work develops Rational Method Prime (RMP) that follows the basic principle of RM but instead recalculates catchment variables by taking into account runoff control effects and evaluates runoff control efficiencies by using two indices. RMP has three merits: (1) providing an integrated response of the whole catchment with runoff controls; (2) interpreting runoff control effects by plotting runoff flow rate-rainfall duration curves; (3) connecting the design of runoff controls and storm sewers that are based on different design principles and rainfall statistics. Case study results showed that runoff controls reduced peak flow rates by 5.83–91.6%, corresponding to reduction factors for return period of maximum flow rate from 0.04 to 0.76. Indeed, the original RM is based on four assumptions, which also cause its weakness, and there have been current methods to address 3 of them. RMP contributes to addressing the last assumption (i.e. constant catchment imperviousness), which finally allowing the evolution from RM 1.0 to 2.0.

Catchment response to climate and land use changes in the Upper Blue Nile sub-basins, Ethiopia

The impacts of climate and land development on streamflow and water balance components were analyzed in the Tana and Beles watersheds by using the Soil and Water Assessment Tool (SWAT). Streamflow response to simultaneous future land-use and land-cover (fLULC) and climate change (fCC) scenarios on the seasonal scale varied among the key water abstraction locations. The General Circulation Models (GCMs) average simulation of short-term climate indicated wetter and warmer climatic condition compared to that in the baseline period (1971/1980–2013). The near–future climate scenario would intensify extreme flow by increasing rainy season flow and reducing dry period flow. However, conversion of cultivation land on steep slope into forest might mitigate these extreme flows. At the outlet of Tana watershed, streamflow response would be amplified under concurrent scenarios of fLULC and fCC; but the streamflow would have an augmenting response at the outlet of the Beles watershed. Compared to response due to fCC alone, the streamflow and surface runoff components under combined fLULC and fCC scenarios would be alleviated in sub-catchments subject to conversion of cultivation in steep slope into forest land. The present results have significances for water resource management and land use planning in the Tana and Beles watersheds, and for other regions encountering identical pressures from climate change and LULC dynamics. In view of ongoing land use and climate dynamics, environmental policies must be carried out to cope with the potential changes of hydrologic regime. Moreover, catchment management should be adapted to changing hydrological regimes at different water abstraction points.

Effects of Drainage and Subsequent Restoration on Peatland Hydrological Processes at Catchment Scale

AbstractPotential benefits of peatland restoration by rewetting include carbon sequestration, restored biodiversity, and improved hydrological functions. There is great uncertainty about how catchment hydrological processes change after restoration, with a particular lack of well‐documented catchment runoff data. This study compared five formerly Disturbed (now Restored) and two undisturbed peatlands. In total, 455 and 728 hydrological events were selected for the analysis, using a three‐event selection technique. Mean event runoff coefficient (RC) values varied greatly between conditions and hydrological events. RC in Disturbed conditions was slightly higher than in undisturbed conditions, but RC in Restored conditions was higher than under other conditions. Mean transit time revealed that event rainfall water reached the outlet faster in Disturbed conditions. Mean event peak flow in Disturbed conditions was higher and peaked faster than under other conditions. However, the base flow showed no noticeable difference between treatments. Significantly higher watertable (WT) rise per rainfall input (0.36–0.85 cm/mm) was observed in Disturbed conditions, due to lower specific yield (Sy) values (0.13–0.24) than under Restored and undisturbed conditions (Sy 0.25–0.50). Shallow WT showed significant positive correlations with runoff and storage properties and was a key component of the runoff generation mechanisms in peatlands. Storage‐related parameters (Sy, WT rise per rainfall input) and catchment response time parameters revealed disturbance‐related hydrological changes in peatlands more clearly than other runoff parameters tested (e.g., RC). Overall, with restoration, WT and storage properties recovered to the levels at undisturbed sites but increased runoff was observed occasionally due to wetter antecedent moisture conditions.

Direct response of small non-glaciated headwater catchments to Late Quaternary climate change: The Valle de la Fueva, southern Pyrenees

Topographic depressions in mountain regions function as sediment traps and their morpho-sedimentary archives provide important insight into erosion and sediment dynamics in mountain ranges. In order to establish the (direct) drivers and timing of erosion phases in the southern central Pyrenees, small non-glaciated headwater catchments in the highly erodible Valle de la Fueva drainage basin were investigated as to their morphogenetic development.Geomorphic mapping revealed three morphogenetic complexes associated with the Valle de la Fueva drainage basin development: (i) high-lying talus plateaus and lateral slopes, (ii) extensive glacis and pedimentation surfaces, and (iii) deeply incised ravines with late-stage fluvial-cut terraces. The talus slopes are the oldest preserved geomorphic units of the Valle de la Fueva and potentially denote the initial drainage basin topography. Talus bedrock and boulder exposure ages cluster yet between 21 and 40 10Be-ka, indicating that the carbonate-dominated talus surfaces were rejuvenated during the last glacial cycle (MIS 4–MIS 2). The younger morphogenetic complexes (ii, iii) point to successive basin erosion stages from diffusive surface pedimentation under cold climate conditions (ii) to rapid linear fluvial dissection and late-stage terrace formation (iii). Denoting the abandonment of pediments as actively eroding surfaces, 10Be depth profiles of glacis cover sediments yielded consistent late MIS 2 exposure ages. The abandoning of pediments marks the onset of rapid fluvial downcutting of deep ravines (iii) around the Holocene climate transition, which involved substantial sediment routing and basin scale erosion. Lower fluvial-cut terraces denote the termination of intense catchment erosion at around 14–8–10Be-ka and minor fluvial incision during Middle-Late Holocene.This research shows that small non-glaciated mountain catchments feature valuable high-resolution morpho-sedimentary archives that are useful for assessing the direct impact of major climate transitions on surface processes and landscape transformation in mountain regions. Improvements in quantifying the timing and rates of (paleo-) surface processes are vital for enhancing regional glaciofluvial chronologies and large-scale basin erosion models that are possibly afflicted with time-averaging biases.

A Hydrological Response Analysis Considering Climatic Variability: Case Study of Hunza Catchment

The hydrological response of mountainous catchments particularly dependent on melting runoff is very vulnerable to climatic variability. This study is an attempt to assess hydrological response towards climatic variability of the Hunza catchment located in the mountainous chain of greater Hindu Kush-Himalaya (HKH) region. The hydrological response is analyzed through changes in snowmelt, ice melt and total runoff simulated through the application of the hydrological modeling system PREVAH under hypothetically developed climate change scenarios. The developed scenarios are based on changes in precipitation (Prp) and temperature (Tmp) and their combination. Under all the warmer scenarios, the increase in temperature systematically decreases the mean annual snow melt and increases significantly glacier melt volume. Temperature changes from 1°C to 4°C produce a large increase in spring and summer runoff, while no major variation was observed in the winter and autumn runoff. The maximum seasonal changes recorded under the Tmp+4°C, Prp+10% scenario.

Flood hydrograph simulation in ungaged basins: modeling linear–nonlinear storage-discharge relationships in a semiarid mountain region

ABSTRACTFor the purpose of flood mitigation in a mountain region, this study aims to evaluate the degree of nonlinearity in the hydrologic storage-discharge relationship. The study area includes a mesoscale catchment, its headwater subcatchment, and its large-scale parent basin in the Zagros mountain region of southwestern Iran. Rainfall events are divided into two variable classes, Low Temporal (LT) and High Temporal (HT), based on their heterogeneity across time. For Low Temporal rainfall events, the mesoscale catchment and its headwater subcatchment show strong nonlinear behavior, but their responses tend to be less nonlinear for High Temporal rainfall events. Meanwhile, for High Temporal events, soil moisture has a dominant role in catchment response. On the other hand, a different perspective is drawn for the larger basin because a strong nonlinear response is obtained for all events regardless of temporal heterogeneities and soil moisture conditions, emphasizing the filtering effect of catchment extent on the rainfall–runoff process.

Effects of differential hillslope‐scale water retention characteristics on rainfall–runoff response at the Landscape Evolution Observatory

AbstractHillslopes turn precipitation into runoff and thus exert important controls on various Earth system processes. It remains difficult to collect reliable data necessary for understanding and modeling these Earth system processes in real catchments. To overcome this problem, controlled experiments are being conducted at the Landscape Evolution Observatory at Biosphere 2, The University of Arizona. Previous experiments have revealed differences in hydrological response between 2 landscapes within Landscape Evolution Observatory, even though both landscapes were designed to be identical. In an attempt to discover where the observed differences stem from, we use a fully 3‐dimensional hydrological model (CATchment HYdrology) to show the effect of soil water retention characteristics and saturated hydraulic conductivity on the hydrological response of these 2 hillslopes. We also show that soil water retention characteristics can be derived at hillslope scale from experimental observations of soil moisture and matric potential. It is found that differences in soil packing between the 2 landscapes may be responsible for the observed differences in hydrological response. This modeling study also suggests that soil water retention characteristics and saturated hydraulic conductivity have a profound effect on rainfall–runoff processes at hillslope scale and that parametrization of a single hillslope may be a promising step in modeling rainfall–runoff response in real catchments.

Reference Time of Concentration Estimation for Ungauged Catchments

Accurate modelling of flood flow hydrographs in ungauged catchments is a challenging task due to large errors in the estimation of its response time using existing empirical equations. The time of concentration (Tc) is a key catchment response time parameter needed for forecasting of the peak discharge rate and the timing of the flood event. At least eight different definitions have been presented in the literature for the time of concentration. In this study, a new definition of “Reference Tc” is presented along with a practical procedure for its estimation using readily available basin catchment characteristic parameters with the aim of standardizing this key parameter for practitioners. Nine different empirical models were calibrated and tested on nine catchments of the Credit River watershed, Ontario, Canada to determine which method would provide the most accurate prediction of the Reference Tc. The NRCS velocity method (1986) proved once again to be the most reliable and an accurate method. This study shows that the main reason for the higher accuracy of the NRCS velocity method predictions compared to the empirical equations is attributed to the inclusion of the Manning's roughness coefficient.

Evaluating catchment response to artificial rainfall from four weather generators for present and future climate.

The technical lifetime of urban water infrastructure has a duration where climate change has to be considered when alterations to the system are planned. Also, models for urban water management are reaching a very high complexity level with, for example, decentralized stormwater control measures being included. These systems have to be evaluated under as close-to-real conditions as possible. Long term statistics (LTS) modelling with observational data is the most close-to-real solution for present climate conditions, but for future climate conditions artificial rainfall time series from weather generators (WGs) have to be used. In this study, we ran LTS simulations with four different WG products for both present and future conditions on two different catchments. For the present conditions, all WG products result in realistic catchment responses when it comes to the number of full flowing pipes and the number and volume of combined sewer overflows (CSOs). For future conditions, the differences in the WGs representation of the expectations to climate change is evident. Nonetheless, all future results indicate that the catchments will have to handle more events that utilize the full capacity of the drainage systems. Generally, WG products are relevant to use in planning of future changes to sewer systems.

Demonstrating the “unit hydrograph” and flow routing processes involving active student participation – a university lecture experiment

Abstract. The unit hydrograph (UH) has been one of the most widely employed hydrological modelling techniques to predict rainfall–runoff behaviour of hydrological catchments, and is still used to this day. Its concept is based on the idea that a unit of effective precipitation per time unit (e.g. mm h−1) will always lead to a specific catchment response in runoff. Given its relevance, the UH is an important topic that is addressed in most (engineering) hydrology courses at all academic levels. While the principles of the UH seem to be simple and easy to understand, teaching experiences in the past suggest strong difficulties in students' perception of the UH theory and application. In order to facilitate a deeper understanding of the theory and application of the UH for students, we developed a simple and cheap lecture theatre experiment which involved active student participation. The seating of the students in the lecture theatre represented the “hydrological catchment” in its size and form. A set of plastic balls, prepared with a piece of magnetic strip to be tacked to any white/black board, each represented a unit amount of effective precipitation. The balls are evenly distributed over the lecture theatre and routed by some given rules down the catchment to the “catchment outlet”, where the resulting hydrograph is monitored and illustrated at the black/white board. The experiment allowed an illustration of the underlying principles of the UH, including stationarity, linearity, and superposition of the generated runoff and subsequent routing. In addition, some variations of the experimental setup extended the UH concept to demonstrate the impact of elevation, different runoff regimes, and non-uniform precipitation events on the resulting hydrograph. In summary, our own experience in the classroom, a first set of student exams, as well as student feedback and formal evaluation suggest that the integration of such an experiment deepened the learning experience by active participation. The experiment also initialized a more experienced based discussion of the theory and assumptions behind the UH. Finally, the experiment was a welcome break within a 3 h lecture setting, and great fun to prepare and run.

Applications of the PyTOPKAPI model to ungauged catchments

Many catchments in developing countries are poorly gauged/totally ungauged which hinders water resource management and flood prediction in these countries. This study explored the application of the PyTOPKAPI model to South African (Mhlanga) and Ethiopian (Gilgel Ghibe) case study catchments to test its suitability for simulating stream flows from ungauged catchments. The aim is to extend the model application to poorly gauged/totally ungauged catchments in developing countries. The model uses digital elevation data and other spatial data sources to set up the model parameters and the forcing files. To generate reliable stream flows, models generally need to be calibrated, which typically relies on the availability of reliable stream flow data. We show how application of simple lumped models for average runoff ratios, such as that proposed by Schreiber in 1904, can be used as an alternative to detailed calibration with gauged flows. This approach seems to be new; and we show how the proposed method, together with the PyTOPKAPI model, can be used to predict runoff responses in ungauged catchments for water resource applications and flood forecasting in developing countries.

Impact of irrigation on the water level of Lake Maybar, Northeast Ethiopia

ABSTRACTThe main objective of the research is to investigate the impact of irrigation water use on the water level of Lake Maybar. The collected data were tested for their consistency using outlier test and then analysed to estimate the components of catchment and lake water balances. Water Balance (WTRBLN) software was used to simulate the observed flow (catchment response) at the outlet of river Kori Sheleko. The model performance was tested using a Nash–Sutcliffe correlation, R2, and showed better agreement (R2 = 94.3%) between observed and predicted flows. The lake water balance at two scenarios of development of irrigation within Maybar Lake Basin was analysed. The result at scenario-1 (existing irrigation development) showed a water level reduction of about 0.76 m, and at scenario-2 (exploitation of all potential irrigation areas) it was 1.49 m. Through this impact study using a Water Balance Model, it was shown that the consumptive water use for irrigation development heavily affected the natural water level of Lake Maybar.

Conditioning a Hydrologic Model Using Patterns of Remotely Sensed Land Surface Temperature

AbstractHydrologic models are usually calibrated using observed river runoff at catchment outlets. Streamflow, however, represents an integral response of the entire catchment and is observed at a few locations worldwide. Parameter estimation based on streamflow has the disadvantage that it does not consider the spatiotemporal variability of hydrologic states and fluxes such as evapotranspiration. Remotely sensed data, in contrast, include these variabilities and are broadly available. In this study, we assess the predictive skill of satellite‐derived land surface temperature (Ts) with respect to river runoff (Q). We developed a bias‐insensitive pattern‐matching criterion to focus the parameter optimization on spatial patterns of Ts. The proposed method is extensively tested in six distinct large German river basins and cross validated in 222 additional basins in Germany. We conclude that land surface temperature calibration outperforms random drawn parameter sets, which could be meaningful for calibrating hydrologic models in ungauged locations. A combined calibration with Q and Ts reduces the root mean squared error in the predicted evapotranspiration by 8% compared to flux tower observations but reduces the NSEs of the streamflow predictions by 6% on average for the six large basins. Our results show that patterns of Ts better constrain model parameters when considered in a calibration next to Q, which finally reduces parametric uncertainty.

Assessment of water sources and their contributions to streamflow by end-member mixing analysis in a subtropical mixed agricultural catchment

Knowledge of the dominant water sources and their relative contributions to streams in time is important for understanding the underlying hydrological processes as well as managing the quantity and quality of water resources. In many subtropical regions, the complexity of mixed agricultural land and water use in combination with lack of data further inhibits such understanding of the dominant catchment scale runoff generation processes. This study provides new insights into the time-variable interactions of natural and anthropogenic influences on the catchment response through integrated hydrometric and multi-tracer (stable water isotopes, Mg2+, Na+, Si4+, Cl−, and Electricity Conductivity) analyses. The combined diagnostic tools of mixing models (DTMM) and end-member mixing analysis (EMMA) were successfully used to evaluate the spatiotemporal variability in key water sources of a subtropical catchment in China. This study site is characterized by rain-fed uplands and irrigated water paddy fields. The EMMA results for one year of data showed that irrigation water, rainwater and ground water were the three main sources, which contributed to 64%, 19% and 17% of the streamflow on average, respectively. However, temporal patterns in rainfall and irrigation practices did cause significant variability in these relative contributions. Overall, we found that routine agricultural practices to optimize crop growth (especially during paddy growth periods) was a more important factor than hydro-meteorological conditions in controlling the regime and properties of water sources. The relatively simple but successful application of EMMA and DTMM in a complex environment demonstrates that it is a valuable approach for understanding water sources and hydrologic processes concerning agricultural or mixed-land use catchments.

A multi-proxy approach to understanding complex responses of salt-lake catchments to climate variability and human pressure: A Late Quaternary case study from south-eastern, Spain

This article focuses on a former salt lake in the upper Vinalopó Valley in south-eastern Spain. The study spans the Late Pleistocene through to the Late Holocene, although with particular focus on the period between 11 ka cal BP and 3000 ka cal BP (which spans the Mesolithic and part of the Bronze Age). High resolution multi-proxy analysis (including pollen, non pollen palynomorphs, grain size, X-ray fluorescence and X-ray diffraction) was undertaken on the lake sediments. The results show strong sensitivity to both long term and small changes in the evaporation/precipitation ratio, affecting the surrounding vegetation composition, lake-biota and sediment geochemistry.To summarise the key findings the main general trends identified include: 1) Hyper-saline conditions and low lake levels at the end of the Late Glacial 2) Increasing wetness and temperatures which witnessed an expansion of mesophilic woodland taxa, lake infilling and the establishment of a more perennial lake system at the onset of the Holocene 3) An increase in solar insolation after 9 ka cal BP which saw the re-establishment of pine forests 4) A continued trend towards increasing dryness (climatic optimum) at 7 ka cal BP but with continued freshwater input 5) An increase in sclerophyllous open woody vegetation (anthropogenic?), and increasing wetness (climatic?) is represented in the lake record between 5.9 and 3 ka cal BP 6) The Holocene was also punctuated by several aridity pulses, the most prominent corresponding to the 8.2 ka cal BP event. These events, despite a paucity of well dated archaeological sites in the surrounding area, likely altered the carrying capacity of this area both regionally and locally, particularly during the Mesolithic-Neolithic transition, in terms of fresh water supply for human/animal consumption, wild plant food reserves and suitable land for crop growth.

Hydraulic modeling of flow impact on bridge structures: a case study on Citarum bridge

Flood waves because of the rapid catchment response to high intense rainfall, breaches of flood defenses may induce huge impact forces on structures, causing structural damage or even failures. Overflowing stream that passes over the bridge, it means to discharge flood water level is smaller than the capacity of the river flow. In this study, the researches present the methodological approach of flood modeling on bridge structures. The amount of force that obtained because of the hydrostatic pressure received by the bridge at the time of the flood caused the bridge structure disrupted. This paper presents simulation of flow impact on bridge structures with some event flood conditions. Estimating the hydrostatic pressure developed new model components, to quantify the flow impact on structures. Flow parameters applied the model for analyzing, such as discharge, velocity, and water level or head that effect of bridge structures. The simulation will illustrate the capability of bridge structures with some event flood river and observe the behavior of the flow that occurred during the flood. Hydraulic flood modeling use HEC-RAS for simulation. This modeling will describe the impact on bridge structures. Based on the above modelling resulted, in 2008 has flood effect more than other years on the Citarum Bridge, because its flow overflow on the bridge.