Hydrographic Techniques Research Articles

Derivation of flood hydrographs using SCS synthetic unit hydrograph technique for Housha catchment area

Abstract SCS (Soil Conservation Service) synthetic unit hydrograph technique was used to estimate the storm runoff overflows entering the Housha tunnel. The flood hydrographs were derived under different storm event durations for the ungauged Husha Catchment area. Geomorphological and hydrological parameters of the watershed were extracted using GIS measurement tools. The data identified various parameters (time to peak, time of base, and peak flow) of the synthetic unit hydrograph. The peak discharge (Qp in m3 s−1 cm−1) of rainfall excess for different time durations (5, 10, 20, 30, 60, 120, 180, 360, and 720 minutes) was estimated. The results revealed that the peak discharge (Qp) decreased with the increase in time of rainfall excess. The maximum peak discharge (27.5 in m3 s−1 cm−1) was reached 84 minutes after the beginning of the rainfall storm for 5 minutes of rainfall excess whereas the minimum peak discharge (5.2 in m3 s−1 cm−1) was reached after 7 hours and 22 minutes for 12 hours of rainfall excess. Geographic information system (GIS) data-based SCS synthetic unit hydrograph model was verified by comparing the simulated runoff with the estimated runoff from measured rainfall data of the watershed.

Hydrologic response analysis to calculate water yield of Cileungsi River

The study of watershed hydrological response is essentially to understand the hydrological characteristics produced by specific rainfall on the watershed area. These flow parameters also rely on watershed factors such as land use, soil type, and watershed morphometry. The research was performed in the Cileungsi watershed, Bogor Regency, West Java. This research aimed to determine the hydrological response and to investigate the water yield of the Cileungsi watershed. Distributed hydrological modelling was used. Curve Numbers (CN) were estimated using SCS-UH triangular hydrograph technique, while the baseflow was determined using the exponential recession method. Muskingum-Cunge flow routing techniques were used to calculate the flow hydrograph. Yearly water yield was estimated based on measured rainfall data. The simulated hydrograph of several flood event shows similarities to the measured hydrograph. It is based on calibration and optimization of the model parameters. The objective function values are less than 15 percent, with peak discharge range from 654-1,729 m3/second. The hydrograph form tends to feature a rising limb that climbs rapidly with a sloping recession limb. The result of this research shows that the Cilengsi water yield are 4,520.33 mm.

Matthew Flinders and the Charting of Australia’s Coasts, 1798–1814

This article argues that the connections between the maritime explorer Matthew Flinders, the hydrographer Alexander Dalrymple, the mapmaker Aaron Arrowsmith, and the President of the Royal Society, Sir Joseph Banks, were crucial for improved knowledge about Australia’s coastal geography and cartography in the early nineteenth century. It also explains how geographical knowledge of Australia was advanced by the techniques followed by these individuals as part of their professional association. Flinders’s naval career was mainly focused on navigation and exploration in Australian waters. He undertook (with George Bass) the first circumnavigation of Van Diemen’s Land in 1798–1799, proving it was an island. Flinders led the first voyage to circumnavigate Australia in HMS Investigator between 1801 and 1803. He used the latest scientific instruments and hydrographic techniques to explore Australia’s coastline. Drawing on the patronage of Banks and the hydrographical expertise of Dalrymple, Flinders and Arrowsmith combined their talents to produce a highly accurate atlas of Australia to accompany Flinders’s A Voyage to Terra Australis (1814).

ESTIMATING STORM DIRECT RUNOFF USING SYNTHETIC UNIT HYDROGRAPH METHODS BY (WMS) MODEL (SOLAG BASIN AS A CASE STUDY)

The Storm Runoff Volume and its Peak are important for designing and operating dams and different hydraulic structures. Watershed Modeling System (WMS) version (8.1) and The HEC-1 v (4.1) hydrological models were used in this study to estimate the Synthetic runoff hydrograph resulting from two storm events over Solag Basin which is located in Sinjar District north of Iraq, making use of available recorded storms rainfall and Synthetic unit hydrograph technique. Direct runoff hydrographs are determined using Natural Resources Conservation Service (NRCS), Snyder Synthetic Unit Hydrograph and Clark methods.Nash model was used to compare the efficiency of the Synthetic runoff Hydrograph using both Synthetic and recorded discharge data for Solag basin which were available for two storms within water years 1991-1992. Synthetic unit hydrographs are important in flood studies and water resources management.

Evaluation of Non Damaging Flow for a Set of Upstream Sub Basins in a River System

<p class="emsd"><span lang="EN-GB">A model for evaluating non damaging flow for a set of sub basins in a river system is presented. Linear Programming technique incorporating multiple inflows routing scheme is employed to evaluate upstream flow conditions necessary for satisfying specified downstream flood flow conditions. Non damaging flow for the sub basins are determined by using river system properties. The model is applied to a river system in India having flows from gauged and ungauged sub basins; flow contributions from the ungauged basins are estimated by using unit hydrograph technique. Peak flow studies involving major and minor sub basins indicate relative importance of the basins in the study area. Results obtained in the study depict variations in the non-damaging flow with the flow in the main channel. Model applications show that for flood with peaks exceeding 7566 m<sup>3</sup>/s regulating intervening basins only may not lead to safe flow at the downstream section(s). The model allows evaluating effectiveness of controlling the intervening basins in a river system; model applications to a real life river system yield results that are useful in adopting flood control measures for the study area.</span></p>

An assessment of recharge estimates from stream and well data and from a coupled surface-water/groundwater model for the des Anglais catchment, Quebec (Canada)

Estimation of groundwater recharge is of critical importance for effective management of freshwater resources. Three common and distinct approaches for calculating recharge rely on techniques of baseflow separation, well hydrograph analysis, and numerical modeling. In this study, these three methods are assessed for a watershed in southwestern Quebec, Canada. A physically based surface–subsurface model provides estimates of spatially distributed recharge; two baseflow separation filters estimate recharge from measured streamflow; and a well hydrograph master recession curve technique calculates recharge from water-table elevation records. The recharge results obtained are in good agreement over the entire catchment, producing an annual aquifer recharge of 10–30 % of rainfall. The annual average estimated across all methods is 200 mm/year. High variability is obtained for the monthly and seasonal recharge patterns (e.g. respectively, 0–30 mm for September and 0–95 mm for the summer), in particular between the baseflow filters and the well hydrograph technique and between the hydrograph technique and the simulated estimates at the observation wells. Recharge occurs predominantly in the spring months for the different approaches, except for the master recession curve method for which the highest recharge estimates are obtained during the summer. The recharge distribution obtained with the model shows that the main recharge area of the aquifer is the Covey Hill region. The use of a fully integrated physically based model enables the construction of an arbitrary number of well hydrographs to enhance the representativity of the master recession curve technique.

Comparison of Different Hydrograph Routing Techniques in XPSTORM Modelling Software: A Case Study

A variety of routing techniques are available to develop surface runoff hydrographs from rainfall. The selection of runoff routing method is very vital as it is directly related to the type of watershed and the required degree of accuracy. There are different modelling softwares available to explore the rainfall-runoff process in urban areas. XPSTORM, a link-node based, integrated stormwater modelling software, has been used in this study for developing surface runoff hydrograph for a Golf course area located in Rockhampton in Central Queensland in Australia. Four commonly used methods, namely SWMM runoff, Kinematic wave, Laurenson, and Time-Area are employed to generate runoff hydrograph for design storm of this study area. In runoff mode of XPSTORM, the rainfall, infiltration, evaporation and depression storage for subcatchments were simulated and the runoff from the subcatchment to collection node was calculated. The simulation results are presented, discussed and compared. The total surface runoff generated by SWMM runoff, Kinematic wave and Time-Area methods are found to be reasonably close, which indicates any of these methods can be used for developing runoff hydrograph of the study area. Laurenson method produces a comparatively less amount of surface runoff, however, it creates highest peak of surface runoff among all which may be suitable for hilly region. Although the Laurenson hydrograph technique is widely acceptable surface runoff routing technique in Queensland (Australia), extensive investigation is recommended with detailed topographic and hydrologic data in order to assess its suitability for use in the case study area. Keywords—ARI, design storm, IFD, rainfall temporal pattern, routing techniques, surface runoff, XPSTORM.

Reservoir site evaluation through routing

Reservoir routing was conducted for site evaluation of a proposed surface reservoir to be located in an ungauged watershed. The study was part of an integrated approach to the development of the watershed. Nash's synthetic hydrograph technique was used in developing the unit hydrograph, from which the 25-yr, 24-hr storm hydrograph was obtained using convolution procedures. The rainfall excess on the watershed was determined using the Curve Number method while Muskingum's method was used for flood routing through the watershed. A weighted Curve Number of 73 (with potential storage of 94 mm) was obtained – which reflected the agricultural nature of the study basin. The reservoir characteristics were determined from the contour map of the site. Flow estimates were also made from the flood routing results. For the 25- yr, 24-hr storm; the peak inflow into the reservoir was 0.73 m3/s with a peak outflow of 0.43 m3/s, resulting in an attenuation of 0.30 m3/s, and a relative attenuation of 41.10%. Also; the reservoir would not be overtopped since the 99.54 m water elevation for the 25-yr, 24-hr storm was below the reservoir embankment top elevation. Keywords:Reservoir routing Journal of Modeling, Design and Management of Engineering Systems Vol. 3 (1) 2005: pp. 53-62

Boston Harbour Drained: A Case Study Using Hydrographic Systems ToAssess Potential Cultural Resource Sites

A recent navigation project in Boston Harbor, Massachusetts illustrated the use of different hydrographic techniques in assessing cultural resources. The NOAA Ship WHITING, a hydrographic research vessel for the U.S. Department of Commerce's, National Oceanic and Atmospheric Administration, surveyed the entire harbor and its approaches. The main goal of the project was to update the nautical charts for safe navigation. However, the hydrographic team also addressed areas of cultural significance, with particular attention paid to the inner harbor waterfront, the harbor's islands, and shipwrecks located in the waterways. Several remote sensing techniques were used; tools and expertise that are currently being under utilized by the submerged cultural resource community. This paper does not highlight the history of Boston Harbor, but rather use it as a backdrop for how best to survey an historical harbor given the appropriate tools and proper planning. It also stresses the need for archaeological expertise in hydrographic surveying.

Computation and visualization of regional-scale forest disturbance and associated dissolved nitrogen export from Shenandoah National Park, Virginia.

Long-term watershed research conducted in Shenandoah National Park (SNP) in Virginia and elsewhere in the eastern U.S. indicates that annual export of dissolved nitrogen (N) from gaged forested watersheds to surface waters increases dramatically in response to vegetation disturbances. Dissolved N leakage is a common, well-documented response of small forested watersheds to logging in the larger region, while recent defoliation outbreaks of the gypsy moth (Lymantria dispar) larva in the deciduous forests of SNP have been shown to generate similar biogeochemical responses. A recent modeling analysis further suggests that a parsimonious, empirical, unit N export response function (UNERF) model can explain large percentages of the temporal variation in annual N export from a group of small gaged forested watersheds in the years following disturbance. The empirical UNERF modeling approach is completely analogous to the unit hydrograph technique for describing storm runoff, with the model representing annual N export as a linear deterministic process both in space and in time. The purposes of this analysis are to (1) test the applicability of the UNERF model using quarterly streamwater nitrate data from a group of ungaged watersheds in SNP; (2) demonstrate a park-wide application of a regional UNERF model that references the geographic distributions of bedrock geology and the timing and extent of gypsy moth defoliation over the entire SNP area; and (3) visualize the temporal and spatial patterns in vegetation disturbance and annual dissolved N export through the use of computer animation software. During water year 1992, the year of peak defoliation, our modeling study suggests that park-wide export had transiently increased by 1700% from a baseline rate of about 0.1 kg/ha/year. SNP forests appear to be characteristic of other N-limited second-growth forests in the eastern U.S. that leak little N under undisturbed conditions, despite receiving relatively large inputs of N from atmospheric deposition sources. Vegetation disturbances can apparently cause major changes in N input-output balances with potentially important ramifications for low-order forest streams and downstream receiving waters.

Scattering from frontal structures, internal tides, and internal waves during the 1992 Barents Sea polar front experiment

In August 1992, a coastal ocean tomography experiment was conducted in the Barents Sea over the steep northwestern slope of the Bear Island Trough, about 100 km east of Bear Island. The oceanographic objective of the experiment was to study the dynamics of the polar front and its vicinity using both acoustic tomography and traditional hydrographic techniques. The acoustic objective was to study the effects of the front and other coastal oceanography on the acoustic propagation. These objectives are strongly coupled, in that to effectively perform an inverse for the ocean features, one must first obtain a good understanding of the ‘‘forward problem.’’ In this paper, the effect of the strong frontal interface is examined, including its corrugations (‘‘interleaving’’ features), internal tides, and internal waves on the observed acoustic propagation. Effects on both the modal and ray propagation pictures will be examined, using both theoretical predictions and experimental data.

Tomographic measurements of frontal variability in the Barents Sea

In August 1992 a coastal ocean tomography experiment was conducted in the Barents Sea over the steep northwestern slope of the Bear Island Trough, about 100 km east of Bear Island. The objective of the experiment was to map and study the oscillations of the Barents Sea Polar Front using acoustic tomography coupled with traditional hydrographic techniques. Because mesoscale ocean variability has shorter spatial and temporal scales in a coastal environment, a vertical receiving array and frequently transmitting tomography sound sources were used to achieve an enhanced system resolution appropriate for coastal monitoring. The vertical array data were processed using plane‐wave beamforming to separate ray arrivals in both time and angle. In addition, modal arrivals were separated using broadband modal beamforming techniques. The processed travel time data were then ‘‘inverted’’ using a hybrid ray‐mode inverse technique to produce a time series of maps of the polar front. In this presentation, the hybrid ray‐mode inverse method and the frontal variability as imaged by this shallow‐water tomography system are discussed. [Work supported by ONR 1125AR.]

The design storm concept in flood control design and planning

The design storm approach, where the subject criterion variable is evaluated by using a synthetic storm pattern composed of identical return frequencies of storm pattern input, is shown to be an effective approximation to a considerably more complex probabilistic model. The single area unit hydrograph technique is shown to be an accurate mathematical model of a highly discretized catchment with linear routing for channel flow approximation, and effective rainfalls in subareas which are linear with respect to effective rainfall output for a selected “loss” function. The use of a simple “loss” function which directly equates to the distribution of rainfall depth-duration statistics (such as a constant fraction of rainfall, or a ϕ-index model) is shown to allow the pooling of data and thereby provide a higher level of statistical significance (in estimating T-year outputs for a hydrologic criterion variable) than use of an arbitrary “loss” function. The above design storm unit hydrograph approach is shown to provide the T-year estimate of a criterion variable when using rainfall data to estimate runoff.

Run Hydrographs for Prediction of Flood Hydrographs

A bivariate lognormal probability distribution in flood peaks and flood volumes describes families of flood hydrographs, each family with a desired return period. Truncated series of floods are used to estimate the underlying population parameters. The method provides more information on floods than conventional methods, and the theory is illustrated with a worked example. Run hydrograph theory was developed and demonstrated for application on fully-gaged catchments. The method allows for the synthesis of the whole family of design hydrographs for each desired return period. In the development of the theory, hydrographs were analyzed as they occur in the record; thus the sample of hydrographs contains many composite hydrographs. This should result in realistic design hydrographs for practical applications. In the estimation of the necessary parameters it was demonstrated how straightforward it can be to calculate the underlying probability distribution parameters from a truncated sample. The run hydrograph technique may also be amenable towards extrapolation to ungaged catchments.

THE DESIGN OF STORM WATER DRAINAGE CHANNELS USING MATHEMATICAL MODEL TECHNIQUES.

This paper describes the hydraulic aspects of the design of drainage schemes, the main arterial branches of which consist of open channels. The TRRL hydrograph technique is applied to the subsidiary pipe network system but a new mathematical model technique is used for the main drainage channels. The spatially varied unsteady flow conditions within these channels are analysed using a full solution of the equations governing continuity, momentum and frictional resistance, the latter being defined in terms of the Colebrook-White transitional law. The new method was used in a feasibility study to determine the optimum drainage system for the proposed Maplin airport-seaport development, and results from this investigation illustrate the method. (A) /TRRL/