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ESC Stream Chapter


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Playfair's Law
-Made in 1802
-Every river appears to consist of a main trunk, fed from a variety of branches, each running in a valley proportioned to its size,
and all of them together forming a system of valleys, communicating with one another.
-a "natural" channelized flow of water.
Water Channel
commonly divided into main channel areas and overbank areas
also referred to as floodplains
a low-lying area near a stream channel, subject to recurrent flooding; alluvial deposits generally mask underlying rock.
Low flow (base flow)
water flow below the surface.
Flood frequency curve
Commonly used for flood estimation.
Recurrence interval
Calculated from the ranking of the flood and the number of years of data.
Factors Affecting the Hydrologic Response
Current Conditions
Precipitation Patterns
Land Use
Channel Changes
the precipitation that is not dircetly infiltrated into the groundwater system.
Overland Flow
-also called surface flow
-the precipitation that either fails to penetrate into the soil or that resurfaces at a later point due to subsurface conditions.
Runoff Rate
rainfall rate minus inflitration capacity
-occurs when rainfall intensity exceeds infiltration capacity.
Infiltration Rate
rainfall rate which is less than infiltration capacity.
tiny channels formed by overland flow.
Three Processes that evolve rills into larger channels.
Deepening, Widening, and Headward Erosion.
Trunk streams
Formed by surface runoff collecting into tributary streams that merge together.
All trunk streams have tributaries that for a stream network.
Base level
the lelevation of the body of water that a stream drains into.
Two base level types
Ultimate (sea level), and Local or temporary
Two types of stream flow
-Laminar flow
-Turbulent flow
Laminar flow
flow that is smooth and parallel with no mixing. Low velocity.
Turbulent flow
Chaotic, erratic flow with abundant mixing and swirling eddies. High velocity.
Stream Energy
-flowing water contains energy (changes from potetial energy to kinetic energy)
-The work of a stream is to transport water and erode/transport sediment.
Velocity of streams
-not uniform in all areas of a channel
-highest velocity occurs in the center of a straight channel.
Discharge equation
-The product of average velocity and wetted channel cross-section area.
- Q=v*A
Stream Gradient
the drop in elevation from a stream's headwaters to its mouth , ideally forming a concave slope.
Factors of Channel Turbulence
Roughness-low...less turbulence...high...greater turbulence
Load-high amount... high caliber.. low amount.. low caliber
Factors of a Channel
Stream Velocity
Channel shape
Stream Gradient
Channel Roughness
Load(amount & caliber)
Stream Erosion Processes
Hydraulic Action
erosive force of sediments suspended in the flow
Sediment particles collide
Hydraulic Action
the force applied by turbulent water
the dissolving of rocks in water
transported material
3 types:
-dissolved load
-suspended load
-bed load
Dissolved load
Ions from mineral weathering
Suspended load
Fine sediments (silt and clay)
Bed load
Larger particles that move by traction on the bed.
Sediment Deposition
caused by a decrease in stream velocity and a reduction in competence.
Progressive changes that accompany streamflow from the headwaters(upstream) to the mouth (downstream)
Increase Downstream
-channel size
Decrease Downstream
-channel roughness
-sediment grain size
-Longitudinal profile

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