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Karst is a type of topography or large-scale landform characterized by numerous collapse
structures visible at the surface as spring or cave openings and sinkholes, and in the subsurface
as caves and smaller solution openings that provide underground drainage; the closed
depressions and collapse structures that dot a karst landscape are the result of chemical
weathering by dissolution of carbonate rocks, principally limestone and dolomite, and less
commonly of evaporate rocks, especially gypsum and anhydrite, in areas of arid and semiarid
climate. Noteworthy limestone areas of karst topography in the United States are the karst
plains and landscapes of Kentucky, the Ozark Plateau of southern Missouri and northern
Arkansas, and the karst plain of northwestern Florida.
Kinematic viscosity, the ratio of the viscosity coefficient to density of a liquid, is a measure of
the ability of streamflow to entrain and transport sediment.
Knickpoint is any interruption or break of a channel gradient, especially a headcut site of abrupt
change or inflection in the longitudinal profile of a stream channel or its valley.
Krotovina, a soils term of Russian origin, is a once-open irregular tubular structure or chamber
made by a burrowing animal, such as a pocket gopher, that subsequently has filled with
sediment from above. 27 L
Lacustrine refers to any feature formed or caused by the processes of a lake; thus, a body of
lacustrine sediment (lake beds) is typically one of mostly fine fluvial sediment that dropped
from suspension as and while the silt-laden streamflow was ponded as lake water.
Laminar flow, as a hydrologic term, is water movement (flow) in which the lines of flow are
essentially constant and in which flow direction at all sites remains nearly unchanged through
time; laminar flow is typical of most ground-water movement whereas most concentrated
flows of stream channels are turbulent. .
Lentic refers to or relates to still or sluggish water such as lakes, ponds, and swamps; lentic
species are organisms that live in still or sluggish water.
Levee (natural) of a stream channel is a broad, low ridge or embankment of coarse silt and sand
that is deposited by a stream on its flood plain and along either bank of its channel; natural
levees are formed by reduced velocity of flood flows as they spill onto flood-plain surfaces and
can no longer transport the coarse fraction of the suspended-sediment load. Especially along
meandering streams, natural levees may be of mappable areal extent; they tend to be relatively
thin bands of silt and sand sloping gently down-valley from the down-valley bank of the channel
from that portion of a meander crossing the valley floor.
Loam is a porous, permeable soil comprised of similar proportions of clay, silt, and sand; loams
generally contain humus (decomposed organic matter) and may have a minor amount of
Loess is a wind-deposited accumulation of terrestrial clastic sediment generally of coarse-clay
to fine-sand sizes but mostly silt; loess bodies tend to be highly erodible, unstratified, and are
mostly derived by deflation and re-deposition of fine, quartzitic sediment from poorly
protected surfaces of till, glacial outwash, fluvial-overbank and lake-bed deposits, and deserts.
Lotic refers to or relates to moving water, especially streamflow; lotic species are organisms
that live in moving water. M
Manning equation is an empirical formula relating stream velocity to controlling variables;
when channel width and depth are included, the simplified formula (in metric units) is
expressed in terms of discharge, Q: Q = [1/n] G1/2 W D5/3, in which n is the roughness
coefficient, G is channel gradient, W is channel width, and D is mean channel depth. For
hydraulic computations, the formula is usually expressed as
Q = [1/n] A R2/3 S1/2, in which n is the roughness coefficient, A is cross-sectional area, R is
hydraulic radius, and S is the energy slope of the reach.
Mass movement is any downslope transfer, through gravitational (inertial) and generally
water-facilitated (viscous) processes, of near-surface soil and rock material; rates of mass
movement range from very slow creep to nearly instantaneous slope failure. 28 Mass wasting is the failure and movement by gravity of a volume of soil, alluvium, rock, or ice
to a downslope site storage; it the result of the process of mass movement.
Mean annual flood is the average flood discharge (m3 s-1) for a specified period or number of
Meander of a stream is one of a series of regular, sharp, freely developing, and sinuous curves,
bends, loops, turns, or windings in the course of a stream; the process of stream meandering is
a means of channel-gradient adjustment through sorting of stored sediment by erosion at the
outside of a bend and deposition, as a point bar, at the inside of the bend.
Meander belt is that area of an alluvial bottomland defined by lines, on both sides of the zone
of activity, drawn tangentially along the points of maximum horizontal extent of the various
meanders in a sequence of meanders.
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This document was uploaded on 02/26/2014 for the course ES 322 at Western Oregon University.
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