The hydrograph shape is reproduced from averaged unit hydrographs (cudworth, 1989) or based on mean dimensionless hydrographs (craig and rankl, 1978) the mean dimensionless hydrographs may be constructed by visually selecting a representative shape of observed or modelled hydrographs of large floods (benito et al, 2011b, figure 35 (c). Storm hydrographs what is the flood hydrograph the flood hydrograph is a means of showing the discharge of a river at a given point (gauging station) over a short period of time. Hydrograph – a graph that shows river discharge and rainfall over time flood – when the capacity of a river to transport water is exceeded and water flows over it’s banks base flow - the baseflow of the river represents the normal day to day discharge of the river and is the consequence of groundwater seeping into the river channel. The table below outlines the major influences on hydrographs and drainage basins: a size of basin, shape and relief size - the smaller the basin the less time it takes for water to drain to the river, resulting in a shorter lag time.
A storm hydrograph is a way of displaying how the discharge of a river can change over time in response to a rainfall event the discharge of a river is just the amount of water passing a certain point every second, and is calculated by multiplying the cross sectional area of the river by its velocity. Shape of a hydrograph certain conditions can cause the line on the hydrograph to be tall and thin and other conditions can cause it to be short and wide peak discharge is the term used to describe the maximum amount of discharge from the river over the period of time recorded this peak. 2 methods for estimating peak discharges and unit hydrographs for streams in the city of charlotte and mecklenburg county, north carolina the three components for estimating a unit hydrograph are the dimensionless unit hydrograph and.
A hydrograph is a graph showing the rate of flow versus time past a specific point in a river, channel, or conduit carrying flow the rate of flow is typically expressed in cubic meters or cubic feet per second (cms or cfs. The science of surface and ground water version 2 ce iit, kharagpur lesson 3 rainfall runoff relationships version 2 ce iit, kharagpur instructional objectives the shape of the hydrograph depends on the characteristics of the catchment the major factors are listed below. Shape of flood hydrograph lag time of flood size of drainage basin nature of geology of drainage basin x –section shape of drainage basin gradient of river land use – agriculture, level of urbanisation, level of industry and the effect on water flow in the river basin. Where, a is the drainage area in square miles q is the runoff volume in inches t p is the time to peak in hours, and q p is the peak flow rate in cfs the peak rate factor of 484 has the inherent assumption that 3/8 of the volume under the unit hydrograph is under the rising limb and the remaining 5/8 of the volume is under the recession limb. Hydrograph – a graph that shows river discharge and rainfall over time flood – when the capacity of a river to transport water is exceeded and water flows over its banks base flow – the base flow of the river represents the normal day to day discharge of the river and is the consequence of groundwater seeping into the river channel.
The main factors affecting hydrograph shape are: 1) drainage characteristics : basin area, basin shape, basin slope, soil type and land use, drainage density, and drainage network topology. Scs curvilinear unit hydrograph method predicts the same unit hydrograph shape for all watersheds the ordinates for the scs dimensionless curvilinear unit hydrograph and the cumulative curve are given in table 11-1 note the mass (volume) under the rising limb (to the point when t/tp=10) is 0375 this means 375% of the. The shape of a hydrograph is determined by the speed in which flood waters are able to reach the river the nature of the drainage basin therefore has a great influence on the way a river responds to a river as it will determine the types and speeds of the flow of water to the river. Synthetic unit hydrograph methods: a critical review pk bhunya,1, sn panda2 and mk goel1 address the suh shapes with more flexibility than the earlier pdfs proposed by  for suh derivation logic community to determine the complete shape of the hydrographs rather than the peak discharges only  since. Hydrograph shape and border irrigation efficiency by a a alazba,t associate member, asce, and d d fangmeier,2 member, asce abstract: sloping borders with free outflow were studied to determine the effect of inflow hydrograph shape on maximum application efficiency.
The shape of the hydrograph greatly depends on the seasonal distribution of rainfall during summer losses due to evaporation may produce a small peak hydrograph on the other hand, in winter, losses are small with the result that even a small intensity storm may produce a. Lesson 6 factors affecting discharge (hydrographs) 17,203 views share like download lesson 6 factors affecting discharge (hydrographs) 1 what is the relationship isbetween precipitation andrunoffflood hydrographs the shape of a hydrograph can be influenced by many things 9. Hydrograph development content this module describes the use of hydrographs, explains the unit hydrograph theory, derives the peak rate shows the impact of rainfall intensity on hydrograph shape however, a' means for constructing hydrographs of runoff from storms of varying intensities and. The shape of a hydrograph is altered by a few different things one factor is the shape of the drainage basin drainage basins come in a wide assortment of shapes. Lecture 6 runoff and hydrograph analysis at the end of the week, students should be able to: draw the resultant hydrograph based on catchment characteristics and rainfall – runoff conditions state and apply base flow separation techniques and estimate direct runoff values derive unit hydrograph.
Scs hydrographs: hydrology studio uses the scs unit hydrograph method for calculating scs runoff hydrographs this method is the same approach as used in tr-20 the shape factor is a user-definable variable the default value is set to 484 and creates a unit hydrograph that has 3/8 of its area under its rising limb this factor is higher in. Related discussions on the student room aqa geog4b june 2014 - morpeth flooding » as aqa geography geog1 17th and geog2 20th may 2016 » similar geography resources. The shape of a hydrograph of a single storm occurring over the drainage area follows a general pattern this pattern shows a period of rise that culminates in a peak, followed by a period of decreasing discharge (called recession) which may, or may not, decrease to zero discharge, depending on the amount of groundwater flow.
Factors affecting the shape of the breach hydrograph include: size and shape of breach, depth of water at the dam, volume of stored water, surface area of reservoir, and shape (especially length) of reservoir. With the calculated t peak and q peak, the flow at each time step is solved for based on the shape of the dimesionless scs unit hydrograph shown in figure 1 resulting in a burst hydrograph for the particular runoff depth. Hydrographs 20th january 2017 explain how afforestation will influence the shape of a hydrograph in areas afforestation the hydrograph will have a low peak discharge this is because there is less water and therefore less water reaches the river, creating a lower peak discharge.