StudentShare
Contact Us
Sign In / Sign Up for FREE
Search
Go to advanced search...
Free

An Analysis Between Two Catchments - Assignment Example

Cite this document
Summary
This assignment "An Analysis Between Two Catchments" presents attention that must be given to the catchments since they have proved that they have a variety of uses; not only provide water but also for hydro-electric power, pumped water transfers, water storage, and also preventing flood…
Download full paper File format: .doc, available for editing
GRAB THE BEST PAPER93% of users find it useful
An Analysis Between Two Catchments
Read Text Preview

Extract of sample "An Analysis Between Two Catchments"

INTRODUCTION Water is vital in order to sustain life and based on this fact, it is important to acquire the knowledge in ways of its proper use and conservation. This is where hydrology comes in. Since hydrology is basically the science of water, its properties and laws, it is a handy tool in addressing the hydrologic cycle of the processes in nature. Such processes include surface runoff and infiltration, rainfall and snowfall, surface water evaporation, surface water exchange (between streams and lakes, etc), and groundwater storage. In this study, I have chosen to analyze, compare and contrast the recorded flow data from two catchments. The first catchment is Thrushel at Tinhay found in west Cornwall. In operation since 1969, shales and sandstones of Carboniferous Culm Measures predominate the catchment and is affected by the Roadford Reservoir (mainly for storage, hydro-electric power and pumped water transfers). The other is Wellington at North Fareham, situated in the southeast of Southampton. The catchment is predominantly mainly of chalk with clays (in Reading Beds) and sands (Bracklesham Beds). It has been in operation since 1951 and has been changed by the careful but increasing urbanization of the area in the headwaters. After analyzing the gathered data, we will be able to develop an understanding of the water resources of the catchments, evaluate flood risks, and to provide further information regarding construction of impoundments. METHODOLOGY Most of the data obtained for this analysis are described in the National River Flow Archives UK. To compare and contrast the two given Catchment Stations, the analysis uses the frequency flow histograms of both catchments. Evaluate the bar charts of the monthly flow characteristics and plot the flow duration curves of the data from both catchments. Using the Weibull and Gringorten formulae, and the Gumbel method to plot the data, we contrast the recorded flow data of both catchment stations. RESULTS Table 1: RANKED ANNUAL PEAK STREAMFLOW OF THRUSHEL AT TINHAY STAION WITH ESTIMATED QUANTILES, EXCEEDENCE PROBABILITIES AND RECURRENCE INTERVALS (1993-2003) YEAR FLOW, m3/s RANK, i ESTIMATED QUANTILE, q = i/ (N+1) EXCEEDENCE PROBABILITIES, 1 - q RECURENCE INTERVAL, 1 / (1 - q) 1994-95 31.29 1 0.091 0.909 1.1 2001-02 32.37 2 0.182 0.818 1.2 1996-97 33.43 3 0.273 0.727 1.4 1995-96 34.59 4 0.364 0.636 1.6 2002-03 35.11 5 0.455 0.545 1.8 1997-98 35.42 6 0.545 0.455 2.2 1993-94 41.28 7 0.636 0.364 2.8 1998-99 62.40 8 0.727 0.273 3.7 1999-00 65.35 9 0.818 0.182 5.5 2000-01 80.58 10 0.909 0.091 11.0 Table 1: RANKED ANNUAL PEAK STREAMFLOW OF WALLINGTON AT NORTH FAREHAM STATION WITH ESTIMATED QUANTILES, EXCEEDENCE PROBABILITIES AND RECURRENCE INTERVALS (1993-2003) YEAR FLOW, m3/s RANK, i ESTIMATED QUANTILE, q = i/ (N+1) EXCEEDENCE PROBABILITIES, 1 - q RECURENCE INTERVAL, 1 / (1 - q) 1996-97 5.77 1 0.091 0.909 1.1 1997-98 10.40 2 0.182 0.818 1.2 2001-02 18.06 3 0.273 0.727 1.4 1995-96 19.03 4 0.364 0.636 1.6 1994-95 20.51 5 0.455 0.545 1.8 2002-03 20.51 6 0.545 0.455 2.2 1998-99 22.31 7 0.636 0.364 2.8 1999-00 24.68 8 0.727 0.273 3.7 2000-01 32.17 9 0.818 0.182 5.5 1993-94 34.56 10 0.909 0.091 11.0 Figure 3: COMPARISON BETWEEN THE FLOWS OF BOTH CATCHMENTS (1993-2003) Figure 4: FLOOD-EXCEEDING PROBABILITY CURVE Figure 5: FLOOD-RECURRENCE INTERVAL CURVE DISCUSSION To estimate the quantiles (probability distribution), first rank each of the streamflows from lowest to highest using the "sort" command in Microsoft Excel; i indicates the rank. Then use the Weibull plotting-position formula to estimate the quantiles (q): q = i / (N + 1), where, i is the rank and N is the total number of observations (# of years in the record). From Tables 1 and 2 we can see that streamflow value of 80.57 and 34.56 cubic meters per second (cms or m3 /s) has a quantile of 0.909, or in other words, 90.9% of the time, streamflows are less than 80.57 and 34.56 m3 /s. Alternatively, we can think of the estimated quantiles in terms of exceedence probabilities. For example, looking again at Table 1 we see that 81.8% of the time streamflows exceed values of 10.2 cfs. Remember that these quantiles provide estimates only for values between i and N and are not very reliable near either limiting value. Nevertheless, this method will suffice for your analysis, but be aware of the limitations. The definition of a 100-year flood is the annual peak discharge with an exceedence probability of 0.01, or 1%. A 10-yearflood has an exceedence probability of 0.1, or 10%. From Table 1and 2 we see that in 2001 and 1993 the daily peak discharge was 80.57 and 34.56 m3 /s with an exceedence probability of 0.091, or 9.1%, which is a value very close to the 10-year flood definition. In fact, we see that the recurrence interval for the annual peak discharge of 80.57 and 34.56 m3 /s is 11 years. In other words, our statistical model (Weibull plotting-position formula) suggests that this event has a return period, T (or recurrence interval), of 11 years. The return period can be estimated using the following relationship: T = 1 / 1 - q To add to the contrasting elements would be their physical characteristics. The Tinhay station, of the CC type, has a three-bay compound Crump profile weir with crests of 3.66m and 10.97m total length with a catchment area totaling to 112.7 km2 and a POT threshold of 27.37m3/s. Its flood banks could contain flow up to 0.96m so there is no problem with floods. With sandstone and shale, it was a natural catchment until the Roadford Reservoir began to fill and affected flow post in 1988. Its upper end needs confirmation with more gaugings but rating development is considered acceptable. It has an indicative suitability for pooling but rating is not confirmed for the highest flows (since flow is contained in the bank, the rating would still be probably acceptable). On the other hand, the North Fareham station, of the FV type, has a flat-V weir which was installed in the year 1991 with a 250m upstream of the M27 river crossing with a total catchment area of 112km2 and a POT threshold of 9.44 m3/s. Current meter measurement is difficult in flood flows due to the bridge across the weir and it also aggravates problems in flooding. It also has a series of interconnected pools with a considerable bank erosion and debris in the channel. There is a high confidence in rating to the 1.24m stage but has a lower confidence because of bypassing. CONCLUSION There are data used are subjected to limitations due to certain factors. The Weibull plotting-position formula to estimate the quantiles are only estimates of the value, thus not very reliable near either limiting value. However, the estimates used in the study are the best available estimate of flows of the present time. In the North Fareham station, there was a loss of flow records in November 1953 due to vandalism and digital data only started in August 1981, in contrast to Tinhay station which started operation already with digital data. Also, the bypassing beyond the structure limit of North Fareham via the upstream eastern bank leads to uncertainty in flows greater than 9.8 m3/s. It could be said through this study there are factors that cause flood risks in catchments beyond it s physical structure. Such might be the intervention of bridges or the present predomination of such sandstones, sand, clay or shale. Finally, this study has shown that attention must be given to the catchments since they have proved that they have a variety of uses; not only provide water but also for hydro-electric power, pumped water transfers, water storage and also preventing flood. REFERENCES Napa County Resource Conservation District. (2006). Hydrology. Retrieved July 22, 2006 from http://www.naparcd.org/hydrotext.htm#hydrointro _________. (2005). Hydrology. Retrieved July 22, 2006 from http://www.everythingbio.com/glos/definition.phpID=1404 Taylor, R. (2006, June 27). Recurrence interval. Retrieved July 22, 2006 from http://www.geog.ucl.ac.uk/rtaylor/data_disk/1002/1002_flood_time_files/fram e.htm#slide0022.htm Croarkin, C. & Tobias, P. (2006, July 18). Engineering statistics handbook. Retrieved July 22, 2006 from http://www.itl.nist.gov/div898/handbook/eda/section3/eda3668.htm Centre For Ecology and Hydrology. (2006). National river flow archive. Retrieved July 22, 2006 from www.nwl.ac.uk/ih/nrfa/index.htm The Environment Agency. (2006). HiFlows-UK. Retrieved July 22, 2006 from www.environment -agency.gov.uk/hiflowsuk Read More
Cite this document
  • APA
  • MLA
  • CHICAGO
(“ENGINEERING HYDROLOGY Assignment Example | Topics and Well Written Essays - 1500 words”, n.d.)
ENGINEERING HYDROLOGY Assignment Example | Topics and Well Written Essays - 1500 words. Retrieved from https://studentshare.org/technology/1512250-engineering-hydrology
(ENGINEERING HYDROLOGY Assignment Example | Topics and Well Written Essays - 1500 Words)
ENGINEERING HYDROLOGY Assignment Example | Topics and Well Written Essays - 1500 Words. https://studentshare.org/technology/1512250-engineering-hydrology.
“ENGINEERING HYDROLOGY Assignment Example | Topics and Well Written Essays - 1500 Words”, n.d. https://studentshare.org/technology/1512250-engineering-hydrology.
  • Cited: 0 times

CHECK THESE SAMPLES OF An Analysis Between Two Catchments

Correlation of Fluvial Sequences in the Mediterranean by Macklin, Fuller, Lewin, Maas

The next section details the eleven catchments that formed the basis of the study and the alluvial geochronologies that are associated with each of these catchment areas.... (a) extensive terraces formed by aggradation in episodes (b) quasi-continuous incision (c)medium-sized basins where the headwaters supported glaciers and(d) alluvial fans or limestone catchments.... This research paper has a two-fold objective; first to construct a provisional correlation of alluvial sequences during the late and middle Pleistocene phases of river alluviation in the Mediterranean basin; a correlation that can also be tested and second, to evaluate the responses of the rivers to the climate changes that have occurred over the past 200,000 years in the Mediterranean basin....
11 Pages (2750 words) Essay

Catchment Health and Management

To determine a range of possible implications of global change on the region of interest, two scenarios were selected for the study: the warm-dry scenario predicted by the GFDL model, and warm scenario obtained from the GISS model.... In the late 1980s, communities in Western Australia became concerned about a number of environmental issues that they felt were being mismanaged by government agencies....
11 Pages (2750 words) Essay

Storm Drainage Design Project

The base lag refers to the time repose of the river with respect to a rainfall which signifies the drainage potential of the catchments.... The two major component of the runoff from the catchment that contributes to the volume of water in the river are the surface flow, which includes all the flows through the surface of the river and sub surface flow component which incorporates all the ground water flow discharges into the river after the onset of a storm....
6 Pages (1500 words) Essay

Storm Drainage Design

Hydrograph analysis is also used to explain various river behaviors such as how a watershed responds to rainfall and how lag time is related to other parameters such as soil conditions and geology.... In this sense, any hydrological analysis heavily relies on the data related to the river and river basin.... Through evapotranspiration, the effect of the stream-aquifer interaction, effects of other hydrologic processes such as interception, and depression storage are altogether ignored for analysis (Ramírez, 2000), other parameters should be appropriately measured for relevant hydrological analysis....
6 Pages (1500 words) Coursework

Catchment Management

The essay "Catchment Management" discovers the effects of a non-stationary climate on a water management system in the Warta River Catchment in Central Poland which already suffers from seasonal water deficits.... ... ... ... The extent to which AEAM, and approaches like it, contribute to the more sustainable use of our land and water resources awaits long-term assessment....
11 Pages (2750 words) Essay

Flood Mathematical Models That Are Used In Flood Modelling

DM contribution to flood flow is not at the same rate as surface runoff thus it is separately analyzed which is done as a requirement in hydrograph analysis.... "Flood Mathematical Models That Are Used In Flood Modelling" paper argues that the use of hydrographs and the data provided on the Nash model provided information that is easy to extrapolated flood plain on base flow....
16 Pages (4000 words) Statistics Project

Parameters in Estimation of the Design of Floods and Catchment Response

The paper "Parameters in Estimation of the Design of Floods and Catchment Response" evaluates different methods of estimating the response time of catchment in the estimation of peak discharge.... In this case, three methods were considered; the time of concentration, the time to peak, and the lag time....
33 Pages (8250 words) Term Paper

Laboratory Analysis: Muttama Catchment

The importance of analyzing the relationship between several of the categories cannot be understated as they hold the key to answering conclusively, whether the potential of eutrophication is undermined or otherwise.... "Laboratory analysis: Muttama Catchment" paper discusses the problems of salinity and the potential for eutrophication in the Muttama catchment....
10 Pages (2500 words) Case Study
sponsored ads
We use cookies to create the best experience for you. Keep on browsing if you are OK with that, or find out how to manage cookies.
Contact Us