present Flow and also Sediment move Stream velocity is the speed of the water in the stream. Units room distance per time (e.g., meter per second or feet per second). Present velocity is best in midstream near the surface and is slowest follow me the currently bed and also banks as result of friction.

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Hydraulic radius (HR or simply R) is the ratio of the cross-sectional area split by the wetted perimeter. For a hypothetical stream through a rectangular cross sectional shape (a stream with a level bottom and also vertical sides) the cross-sectional area is merely the broad multiplied by the depth (W * D). For the same hypothetical stream the wetted perimeter would be the depth plus the broad plus the depth (W + 2D). The higher the cross-sectional area in comparison come the wetted perimeter, the more freely flowing will certainly the stream be because less the the water in the present is in proximity come the friction bed. So as hydraulic radius rises so will certainly velocity (all other factors being equal).Stream discharge is the amount (volume) the water pass by a given point in a specific amount that time. That is calculated together Q = V * A, wherein V is the present velocity and A is the stream"s cross-sectional area. Systems of discharge space volume per time (e.g., m3/sec or million gallons every day, mgpd). At low velocity, particularly if the stream bed is smooth, streams may exhibit laminar flow in which all of the water molecules flow in parallel paths. At greater velocities turbulence is introduced into the flow (turbulent flow). The water molecules don"t follow parallel paths. Streams lug dissolved ion as liquified load, well clay and also silt particles as suspended load, and coarse sands and gravels as bed load. Fine particles will only remain suspended if circulation is turbulent. In laminar flow, suspended corpuscle will slowly settle to the bed.Hjulstrom"s diagram plots 2 curves representing 1) the minimum stream velocity forced to erode sediments of varying sizes from the present bed, and 2) the minimum velocity compelled to continue to deliver sediments of varying sizes. An alert that for coarser sediments (sand and gravel) the takes just a little greater velocity to originally erode particles than it take away to proceed to carry them. For small particles (clay and silt) considerably higer velocities are forced for erosion 보다 for transportation due to the fact that these finer particles have actually cohesion resulting from electrostatic attractions. Think of exactly how sticky wet mud is.

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stream competence refers to the heaviest particles a stream have the right to carry. Currently competence relies on present velocity (as shown on the Hjulstrom diagram above). The much faster the current, the more heavier the particle that deserve to be transported. Stream capacity is the maximum quantity of solid load (bed and suspended) a stream have the right to carry. It relies on both the discharge and also the velocity (since velocity affects the competence and therefore the variety of particle sizes that may be transported).As currently velocity and discharge boost so carry out competence and also capacity. Yet it is not a linear relationship (e.g., doubling velocity and discharge carry out not simply twin competence and also capacity). Competence varies as about the sixth power of velocity. Because that example, copy the velocity outcomes in a 64 times increase in the competence.Capacity varies together the discharge squared or cubed. Therefore tripling the discharge outcomes in a 9 to 27 times boost in the capacity.Therefore, most of the work of streams is completed during floods as soon as stream velocity and discharge (and thus competence and capacity) are numerous times your level throughout low flow regimes. This work-related is in the type of bed scouring (erosion), sediment carry (bed and also suspended loads), and sediment deposition. Stream Dynamics

Perennial and Ephemeral StreamsGaining (effluent) streams receive water from the groundwater. In various other words, a acquiring stream discharges water native the water table. At the same time losing (influent) streams lie over the water table (e.g., in one arid climate) and water seeps v the present bed come recharge the water table below. Getting streams room perennial streams: they flow year around. Shedding streams are frequently ephemeral streams: they do not flow year round. Th. Only circulation when there is enough runoff from current rains or spring snowmelt. Part streams space gaining component of the year and also losing component of the year or simply in details years, together the water table fall during an extended dry season.Streams have actually two sources of water: storm charge, indigenous overland flow after rain events, and baseflow, provided by groundwater.

Flood Erosion and Deposition: together flood waters rise, the steep of the stream together it flows to its base level (e.g., the ocean or a lake) increases. Also, as stream depth increases, the hydraulic radius increases thereby make the currently more complimentary flowing. Both that these factors lead to rise in present velocity. The enhanced velocity and also the enhanced cross-sectional area median that discharge increases. Together discharge and also velocity rise so carry out the stream"s competence and capacity. In the rising stages of a flood much sediment is dumped right into streams through overland flow and gully wash. This can result in part aggradation or building up the sediments ~ above the present bed. However, after the flood peaks much less sediment is carried and also a great deal that bed scouring (erosion) occurs. As the overwhelming subsides and competence and also capacity decrease sediments space deposited and the currently bed aggrades again. Also though the present bed may return to somewhat favor its pre-flood state, large quantities the sediments have actually been transported downstream. Lot fine sediment has actually probably been deposited ~ above the flood plain. Stream PatternsMeandering Streams: At a bend in a currently the water"s momentum carries the mass of the water versus the outer bank. Water piles up on the outer financial institution making the a little deeper and also the inner financial institution a tiny shallower. The greater depth ~ above the external side the the bend also leads to higher velocity at the outer bank. The higher velocity merged with the higher inertial pressure on the outer bank erodes a deepr channel. The depth channel reinforces the velocity increase. The inner bank remains shallower, raising friction, in order to reducing the velocity.

Where the depth and also velocity of the water on the outer bank increase so carry out the competence and capacity. Erosion wake up on the outer bank or cut bank. Where velocity that the water top top the inner bank decreases so do the competence and capacity. Deposition occurs, resulting in the development of a point bar. Over time, the position of the stream alters as the bending migrates in the direction the the reduced bank. As oxbow bends accentuate and also migrate, two bends deserve to erode together developing a cutoff and also leaving an oxbow lake.

Graded Streams: Considering the longitudinal (downstream) file of a stream: where a stream flows under a steep steep velocity will rise which will result in raised erosion. Where that stream climate flows onto a gentler steep velocity decreases and deposition will certainly result. This procedure will minimize the slope of steep stretches and increase the steep of flatter stretches causing a an ext even slope v the food of the stream.


The best graded profile that a currently is concave upward: steeper close to the head or beginning and flatter close to the bottom or mouth of the stream. The factor for this is that in the upper reaches that a present its discharge is smaller. As streams merge with other streams your discharge increases, their cross-sectional area increases, and also their hydraulic radius increases. As one go downstream and also the stream grow in size the waters flow an ext freely. In the top reaches, a little stream have to be steeper to deliver its sediments. The extra gravitational energy on the steeper slope is essential to get over the frictional forces in the shallow stream. If the steep is as well gentle and also velocity is too slow-moving to move the sediments being offered by weathering and also erosion, the sediments will pile up. This boosts the gradient which reasons the water come flow quicker which boosts erosion and also transport, which climate reduces the gradient. In the lower reaches of a stream, wherein the discharge is greater, since friction is much less the stream require not it is in so steep to deliver the load. If it to be steeper than necessary to transfer the sediments erosion would certainly result. Yet this would certainly decrease the gradient causing a diminish in erosion.