What is a storm hydrograph BBC Bitesize? A hydrograph shows two graphs – a bar chart showing rainfall, usually from a storm and a line graph showing discharge from before, during and after the rain storm shown in the bar graph. Basically, a hydrograph shows you the ways in which a river is affected by a storm.
What are the key features of a storm hydrograph? The storm hydrograph plots two things: the occurrence of a short period of rain (maybe a heavy shower or storm) over a drainage basin and the subsequent discharge of a river. Peak discharge is reached some time after the peak rainfall because the water takes time to move over and through the ground to reach the river.
What are the causes of a storm hydrograph? Human Factors Affecting Storm Hydrographs
1. Drainage systems that have been created by humans lead to a short lag time and high peak discharge as water cannot evaporate or infiltrate into the soil. 2. Area that have been urbanised result in an in crease in the use of impermeable building materials.
What is the difference between a storm hydrograph and an annual hydrograph? A storm hydrograph is a specific type of hydrograph that, surprise, surprise, shows precipitation and discharge during and after a storm. The main difference between a normal hydrograph and a storm hydrograph is that a storm hydrograph is over a much shorter period of time.
What is a storm hydrograph BBC Bitesize? – Related Questions
Why is a storm hydrograph important?
Basically, a hydrograph shows you the ways in which a river is affected by a storm. This helps us to understand discharge patterns of a particular drainage basin and helps to predict flooding and plan flood prevention measures. As you can see in the graph below, the peak rainfall is the time of highest rainfall.
How would you describe a storm hydrograph?
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.
What affects the shape of a storm hydrograph?
A number of factors (known as drainage basin controls) influence the way in which a river responds to precipitation and have an effect on the shape of the hydrograph. The size, shape and relief of the basin are important controls.
What increases river discharge?
Discharge changes whenever you add or take away water. In a hot area, some discharge will be lost through evaporation. When it rains, the river’s discharge will increase, too. Last of all, the river’s discharge will increase when another river joins it to make one larger river.
How do humans affect storm Hydrographs?
Human Factors Affecting Storm Hydrographs
Area that have been urbanised result in an in crease in the use of impermeable building materials. This means infiltration levels decrease and surface runnoff increases. This leads to a short lag time and an increase in peak discharge.
What is an annual hydrograph?
An annual hydrograph method is proposed to determine EIA. This involves using existing gauged creek systems and rainfall records from rainfall gauging networks. This enables the use of available data to determine a watershed’s response to rainfall throughout the year, and thereby compute a year-round EIA.
What is S curve hydrograph?
S-curve, or S-curve hydrograph : A graph showing the summation of the ordinates of a series of unit hydrographs spaced at unit-rainfall duration intervals. It represents the hydrograph of unit rate of rainfall excess continued indefinitely.
What is the largest watershed in America?
The Mississippi River watershed is the biggest watershed in the United States, draining more than three million square kilometers (one million square miles) of land.
How do you explain a hydrograph?
A hydrograph is a graph showing the rate of flow (discharge) 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).
Why is lag time so important?
Abstract River basin lag time (LAG), defined as the elapsed time between the occurrence of the centroids of the effective rainfall intensity pattern and the storm runoff hydrograph, is an important factor in determining the time to peak and the peak value of the instantaneous unit hydrograph, IUH.
Who uses a storm hydrograph?
Storm hydrographs are graphs that show how a drainage basin responds to a period of rainfall. They are useful in planning for flood situations and times of drought as they show the discharge (amount of water reaching channel via surface run-off, throughflow, and base flow) that originated as precipitation.
Why can the shape of a storm hydrograph be affected by different land uses?
A circular shaped drainage basin leads to rapid drainage whereas a long drainage basin will take time for the water to reach the river. The steeper the basin the more quickly it drains. Indented landscapes will collect water and reduce runoff rates, reducing the amount of water reaching the river channel.
What is a gentle hydrograph?
A gentle hydrograph shows the river is at low risk of flooding. These types of hydrograph have a gentle rising limb and a long lag time which means it takes longer for the peak rainfall to reach the river channel, so the river discharge is increasing slowly.
How do you separate base flow?
Straight Line Method In this method the separation of the base flow is achieved by joining with a straight line the beginning of the surface runoff to a point on the recession limb representing the end of the direct runoff.
What is a flow hydrograph?
A hydrograph is a graph of the flow in a stream over a period of time. Below is a picture of a hydrograph, with stream flow (discharge) in cubic feet per second on the y-axis and time in months on the x-axis. Peaks in the hydrograph are usually a result of precipitation events, while troughs represent drier times.
Why would a hydrograph have a very short lag time?
Drier conditions mean the rainfall can infiltrate into the soil slowing down lag time. Vegetation – if there is no vegetation in an area, the water runs off into the river quicker, therefore it would have a short lag time.
What does the term 100 year flood really imply?
The term “100-year flood” is used to describe the recurrence interval of floods. The 100-year recurrence interval means that a flood of that magnitude has a one percent chance of occurring in any given year. In other words, the chances that a river will flow as high as the 100-year flood stage this year is 1 in 100.
What does a shorter lag time mean?
A short lag time means water is reaching the river quickly, so there is a greater chance of a flood. Factors influencing lag time include: Size of drainage basin. Vegetation.
What river has the largest discharge in the world?
With more than 1,100 tributaries — 17 of which are over 930 miles (1,497 km) long — the Amazon River has the largest drainage system in the world.
Are humans the cause of floods?
Deforestation. When deforestation occurs in a particular area, there are no more trees to help soak up precipitation and reduce waterflow over the landscape. Without these natural protections, there is an increased risk of flooding and erosion whenever it rains.
How does deforestation affect a storm hydrograph?
Factors affecting the storm hydrograph
storage of water in reservoirs decreases discharge. Urbanisation and deforestation both increase discahrge. Tarmac increases overland flow because it is an impervious surface, and deforestation decreases interception.