How is bankfull discharge calculated?
The resulting equations are: bankfull discharge = 45.3 (drainage area)0.856; bankfull channel width = 13.5 (drainage area)0.449; bankfull channel depth = 0.801 (drainage area)0.373; bankfull channel cross- sectional area = 10.8 (drainage area)0.823.
How is Bankfull cross sectional area calculated?
The total cross-sectional area is determined by adding the area of all the individual trapezoids (Figure 11). Bankfull width is the surface width of the stream measured at the bankfull stage (Figure 7). Bankfull mean depth is computed by dividing the bankfull cross-sectional area by the bankfull width (Figure 8).
What is the meaning of bankfull discharge?
Bankfull discharge is commonly thought of as the flow that fills the channel up to the top of banks, prior to flooding. For undisturbed, poised streams with wide floodplains, this definition would be correct.
Why is bankfull discharge important?
Bankfull discharge is important to watershed managers because it is considered to be the most effective flow for moving sediment, forming or removing bars, forming or changing bends and meanders, and generally doing work that results in the average morphological characteristics of channels (Dunne and Leopold, 1978).
What happens when bankfull discharge is reached?
The bankfull discharge at a river cross-section is, in effect, the discharge that fills the channel to the top of its banks and therefore marks the condition of incipient flooding. Although different definitions exist, this characteristic discharge is accepted as being an important indicator in river management.
How is Bankfull measured?
Bankfull depth is the average distance from the channel bed to the estimated water surface elevation at bankfull flow. With the measuring tape extended across the channel, divide the bankfull width into ten evenly spaced sections (Figure 2). Depth measurements are taken at the center of each section.
What are bankfull conditions?
Bankfull: The water level, or stage, at which a stream, river or lake is at the top of its banks and any further rise would result in water moving into the flood plain.
What is Bankfull area?
“Bankfull depth” means the average vertical distance between the channel bed and the estimated water surface elevation required to completely fill the channel to a point above which water would enter the floodplain or intersect a terrace or hillslope.
How often does bankfull discharge occur?
While an average return period of 1.5 years is often cited for bankfull discharge, this event can occur at intervals of less than one year to more than a decade.
What is bankfull stage?
Bankfull. The water level, or stage, at which a stream, river or lake is at the top of its banks and any further rise would result in water moving into the flood plain.
What is the range of estimated bankfull discharge?
The estimated bankfull discharge using the Jarrett equation (equation 7) (1984) ranged from 69 to 3,678 ft3/s (table 4); that range compares well with the range of estimated bankfull discharges from the primary method in table 3.
How to estimate bankfull channel geometry and discharge?
The common method of estimating bankfull channel geometry and discharge is to relate bankfull width, mean depth, cross-sectional area, and discharge to drainage area through regression equations and graphic plots. The plots of the regression equations for bankfull channel geometry and discharge are commonly referred to as “regional curves.”
What is the range of bankfull discharge from the Jarrett equation?
higher, respectively, for the Limerinos method than for the primary method. The estimated bankfull discharge using the Jarrett equation (equation 7) (1984) ranged from 69 to 3,678 ft3/s (table 4); that range compares well with the range of estimated bankfull discharges from the primary method in table 3.
What is bankfull discharge?
Bankfull discharge is the streamflow that occurs when the stream fills its channel and any additional discharge will result in the stream overflowing its banks. 2 Equations for Estimating Bankfull Channel Geometry and Discharge for Streams in Massachusetts