Inverse of Drainage Density as a Physical Quantity Drainage density can be used to approximate the average length of overland flow in a catchment. Horton (1945) used the following equation to describe the average length of overland flow as a function of drainage density: Elementary Components of Drainage Basins A drainage basin can be defined by three elementary quantities: channels, the hillslope area associated with those channels, and the source areas. The channels are the well-defined segments that efficiently carry water through the catchment. Labeling these features as “channels” rather than “streams” indicates that there need not be a continuous flow of water to capture the behavior of this region as a conduit of water. According to Arthur Strahler’s stream ordering system, the channels are not defined to be any single order or range of orders. Channels of lower orders combine to form higher order channels. The associated hillslope areas are the hillslopes that slope directly into the channels. Precipitation that enters the system on the hillslopes areas and is not lost to infiltration or evapotranspiration enters the channels. The source areas are concave regions of hillslope that are associated with a single channel. Precipitation entering a source area that is not lost to infiltration or evapotranspiration flows through the source area and enters the channel at the channel’s head. Source areas and the hillslope areas associated with channels are differentiated by source areas draining through the channel head, while the associated hillslope areas drain into the rest of the stream. According to Strahler’s stream ordering system, all source areas drain into a primary channel, by the definition of a primary channel. Relation to Water Balance Drainage density is tied to the water balance equation: Relation of Drainage Density to the Hydrograph The discharge through the central stream draining a catchment reflects the drainage density, which makes it a useful diagnostic for predicting the flooding behavior of a catchment following a storm event due to being intimately tied to the hydrograph. The material that overland flow travels over is one factor that influences the speed that water can flow out of a catchment. Water flows significantly slower over hillslopes compared to channels that form to efficiently carry water and other flowing material. According to Horton’s interpretation of half of the inverse of drainage density as the average length of overland flow implies that overland flow in high-drainage environments will reach a fast-flowing channel faster over a shorter range. On the hydrograph, the peak is higher and occurs over a shorter range. This more compact and higher peak is often referred to as being “flashy”. Formula for Drainage Density Montgomery and Dietrich (1989) Montgomery and Dietrich (1989) determined the following equation for drainage density by observing drainage basins in the Tennessee Valley, California: Relation to the Mean Annual Flood Charles Carlston (1963) determined an equation to express the mean annual flood runoff, Q2.33, for a given drainage basin as a function of drainage density. Carlston found a correlation between the two quantities when plotting data from 15 drainage basins and determined the following equation: The Effect of Vegetation on Drainage Density The presence of vegetation in a drainage basin has multiple effects on the drainage density. Vegetation prevents landslides in the source area of a basin that would result in channel formation as well as decrease the range of drainage density values regardless of soil composition. Relation to the Flood Hydrograph The discharge through the central stream draining a catchment reflects the drainage density, which makes it a useful diagnostic for predicting the flooding behavior of a catchment following a storm event due to being intimately tied to the hydrograph. The material that overland flow travels over is one factor that influences the speed that water can flow out of a catchment. Water flows significantly slower over hillslopes compared to channels that form to efficiently carry water and other flowing material. According to Horton’s interpretation of half of the inverse of drainage density as the average length of overland flow implies that overland flow in high-drainage environments will reach a fast-flowing channel faster over a shorter range. On the hydrograph, the peak is higher and occurs over a shorter range. This more compact and higher peak is often referred to as being “flashy”. Effect of Climate Change on Drainage Density Drainage density may also be influenced by climate change. Langbein and Schumm (1958)9 propose an equation for the rate of sediment discharge through catchment as a function of precipitation rate:
Inverse of drainage density as a physical quantity Drainage density can be used to approximate the average length of overland flow in a catchment. Horton (1945) used the following equation to describe the average length of overland flow as a function of drainage density: Elementary components of drainage basins A drainage basin can be defined by three elementary quantities: channels, the hillslope area associated with those channels, and the source areas. The channels are the well-defined segments that efficiently carry water through the catchment. Labeling these features as “channels” rather than “streams” indicates that there need not be a continuous flow of water to capture the behavior of this region as a conduit of water. According to Arthur Strahler’s stream ordering system, the channels are not defined to be any single order or range of orders. Channels of lower orders combine to form higher order channels. The associated hillslope areas are the hillslopes that slope directly into the channels. Precipitation that enters the system on the hillslopes areas and is not lost to infiltration or evapotranspiration enters the channels. The source areas are concave regions of hillslope that are associated with a single channel. Precipitation entering a source area that is not lost to infiltration or evapotranspiration flows through the source area and enters the channel at the channel’s head. Source areas and the hillslope areas associated with channels are differentiated by source areas draining through the channel head, while the associated hillslope areas drain into the rest of the stream. According to Strahler’s stream ordering system, all source areas drain into a primary channel, by the definition of a primary channel. Relation to water balance Drainage density is tied to the water balance equation: Relation to hydrographs The discharge through the central stream draining a catchment reflects the drainage density, which makes it a useful diagnostic for predicting the flooding behavior of a catchment following a storm event due to being intimately tied to the hydrograph. The material that overland flow travels over is one factor that influences the speed that water can flow out of a catchment. Water flows significantly slower over hillslopes compared to channels that form to efficiently carry water and other flowing material. According to Horton’s interpretation of half of the inverse of drainage density as the average length of overland flow implies that overland flow in high-drainage environments will reach a fast-flowing channel faster over a shorter range. On the hydrograph, the peak is higher and occurs over a shorter range. This more compact and higher peak is often referred to as being “flashy”. Formula for drainage density Montgomery and Dietrich (1989) Montgomery and Dietrich (1989) determined the following equation for drainage density by observing drainage basins in the Tennessee Valley, California: Relation to the mean annual flood Charles Carlston (1963) determined an equation to express the mean annual flood runoff, Q2.33, for a given drainage basin as a function of drainage density. Carlston found a correlation between the two quantities when plotting data from 15 drainage basins and determined the following equation: Effect of vegetation on drainage density The presence of vegetation in a drainage basin has multiple effects on the drainage density. Vegetation prevents landslides in the source area of a basin that would result in channel formation as well as decrease the range of drainage density values regardless of soil composition. Relation to flood hydrograph The discharge through the central stream draining a catchment reflects the drainage density, which makes it a useful diagnostic for predicting the flooding behavior of a catchment following a storm event due to being intimately tied to the hydrograph. The material that overland flow travels over is one factor that influences the speed that water can flow out of a catchment. Water flows significantly slower over hillslopes compared to channels that form to efficiently carry water and other flowing material. According to Horton’s interpretation of half of the inverse of drainage density as the average length of overland flow implies that overland flow in high-drainage environments will reach a fast-flowing channel faster over a shorter range. On the hydrograph, the peak is higher and occurs over a shorter range. This more compact and higher peak is often referred to as being “flashy”. Effect of climate change on drainage density Drainage density may also be influenced by climate change. Langbein and Schumm (1958)9 propose an equation for the rate of sediment discharge through catchment as a function of precipitation rate:
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Drainage Density as a Physical Quantity
drainage density as a physical quantity
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Components of Drainage Basins
components of drainage basins
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Water Balance
water balance
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of Drainage Density to the Hydrograph
to hydrographs
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Drainage Density
drainage density
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Mean Annual Flood
mean annual flood
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The Effect of Vegetation on Drainage Density
Effect of vegetation on drainage density
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the Flood Hydrograph
flood hydrograph
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Climate Change on Drainage Density
climate change on drainage density