YOU KNOW all this in your bones. Words that describe the river-related features of our region's landscape are a vocabulary we've absorbed without conscious effort.

Consider the word "confluence." As Pittsburghers, we carry a mental image of our city's iconic Point as the definitive example for the geographic term. We nod with approval when network announcers covering Steelers home games use the term to describe the convergence of waters just outside the open end of Heinz Field, secure in our hometown's lock on the textbook definition.

Because our definition is informed by direct observation of a dynamic landscape feature, we carry a richer and more nuanced understanding of the term than people in other parts of the country. The convergence of flowing waters is certainly central to our definition. But as anyone who has stood on Mount Washington and watched the latte brown waters of the Monongahela and the pea green waters of the Allegheny create a bicolored Ohio will tell you, "confluence" does not necessarily imply an immediate blending of the merged fluids.

The writer Barry Lopez has long explored landscape as a shaping force of both culture and community. He views language as a critical catalyst in that process.

In "Home Ground: Language for an American Landscape," he compiled more than 400 pages worth of terms and definitions for our nation's natural features. The entries, reviewed for accuracy by professional geographers, were written by 45 contemporary writers, according, as Lopez explains, "to his or her sense of what's right, what's important to know." (See homegroundproject.com for more detail.)

Pittsburgh's rivers are cited in the text's definition for "confluence." If the great snowstorm of 2010 had not made travel such a hassle, Mr. Lopez might have checked them in person last month -- he spoke at the Drue Heinz Lectures Series here on Feb. 8.

The book's most important message for us is contained in Mr. Lopez's introduction:

"The language we employ to say what we're looking at or to recall what we've seen, for many English speakers, is now collapsing toward an attenuated list of almost nondescript words -- valley, lake, mountain. Used along with 'like a' these words now stand in for glade, tank, and escarpment. ... At a time when the country's landscapes are increasingly treated as commodities, subjected to a debate over their relative and intrinsic worth, and when city planners, land conservators, real estate developers and indigenous title holders square off every day over the fate of one place or another, this can't be good."

At this time of the year, the strongest case for focusing more attention on our rivers involves their capacity to sometimes override all attempts at control. Well-engineered and strategically managed flood-control reservoirs serve the major tributaries of the Allegheny and Monongahela. Nevertheless, lives, property, water supplies, sewage treatment facilities and transportation systems were all under a very real threat last weekend when weather forecasts predicted the high probability that heavy rains and the rapid melt of a dense snowpack would push our rivers far out of their banks.

The Pittsburgh region's great and ongoing investment in reclaiming riverfronts as accessible public amenities also requires us to give additional consideration to the language we all use to describe these pre-eminent natural features. The tax revenues, foundation funds and individual donations spent or pledged for riverfront reclamation -- along with the vast "sweat equity" of river-focused volunteer labor -- can yet be leveraged to greater community value if we all become better river observers.

The emergence of electronic technologies such as Google Earth have also widened the audience and radically changed both vantage points and viewing places for prospective river watchers. Features not readily apparent in real time to observers at the river's edge or even on adjacent hilltops -- such as the demarcation between shallow near-shore waters and the deep navigation channel -- are revealed in striking clarity by digital images captured by satellite cameras.

The definitions for seven simple riverscape terms below are an attempt to initiate a discussion about how language can help us to better understand the rivers we live along. They are offered in both appreciation for -- and in flat-out imitation of -- Barry Lopez's unique work.

With respect to our rivers, the bank is the ground immediately abutting and rising above the water's surface. Excepting bridges and boats, this is the place where our close river encounters occur. Riverbanks in Pittsburgh vary in shape, slope, composition, vegetative cover and the extent to which they are maintained or neglected. Bank diversity includes the sharp-angled concrete and stone borders of Point State Park, sloping North Shore lawns between PNC Park and Carnegie Science Center, towering vertical walls of active and long-shuttered industrial sites and places where for mile after mile the bank is wooded from the water's edge to the topping railroad terrace.

The "Home Ground" definition includes the maxim that "left bank" and "right bank" are "so called with respect to downstream direction." Deciding exactly where the landward side of a riverbank ends is a matter for debate. The term grabs wider chunks of territory when used in song lyrics or accounts of historic battles. Rest assured: If you are enjoying a walk or bike ride along one of our region's river edge trails, you are up on the bank.

These paired terms denote flowing water's dual actions of erosion and deposition. In the places where a river bends, water flowing along the outside of the curve accelerates, increasing its erosional force and cutting into the bank on that side. Conversely, water flowing along the shorter, inside of the bend slows, dropping much of its load of suspended sediment and building up the bank on that side.

This yin and yang process has been going on along our rivers for a very long time. Once you learn how to read this ongoing river action in local landscapes, you'll see it everywhere: The flat portions of Hazelwood as point bar to a cut bank across the Monongahela on the Hays shore; the Sewickley Bridge linking the cut bank traced by Route 51 to its namesake point bar town.

Linked series of cut banks and point bars are best understood as "energy spent by a river and absorbed by the land." That is the explanation offered by writer and conservationist William de Buys in his "Home Ground" entry for the term meander: "If by virtue of velocity or volume a river has more energy than it needs to accomplish its work, it will spend that energy to reshape its course. Sometimes a river will incise its channel, ultimately lowering its bed, which is a way of diminishing the gradient at which it moves downhill. This in turn diminishes its velocity and the energy it has to spend. In other instances a river will extend its channel laterally by carving a series of curves or meanders."

De Buys traces the origin of the word to the excessively winding Menderes River in western Turkey, a waterway know to the Ancient Greeks as "Maiandros of Phrygia."

The deep winding valleys that hold Pittsburgh's rivers and give form to neighborhoods and nearby towns can be viewed as evidence that our waterways both meandered and deeply incised their channels. The mapping of a broad swath of gravel deposits reveals meandering on a broader scale.

Geologists explain that a thick gravel deposit underlying portions of the city's East End indicates that level portions of Wilkinsburg, Homewood, East Liberty, Shadyside and Oakland, now 200 feet above river level, were once the bed of the wandering Monongahela.

Used here, the term is shorthand for navigation channel, the portion of the river where the miles-long slack water pools created by navigation dams create a barge-traffic shipping lane with a minimum depth of 9 feet. This engineered river-within-a-river is marked and maintained for the full length of the Monongahela and Ohio, but only for the Allegheny's lower 60 miles.

The very presence of the channel precludes the existence of several more natural river features such as rapids and seasonal mudflats. In places with a deep enough river view to include a sequence of widely spaced red and green buoys, it's possible to estimate the channel's borders. Buoys on the left descending side of the channel are red, while those on the right descending side are green.

The places where neighborhood streams surrender their flow to our region's big water are easy to spot from mid-channel. Each stream enters a river across a gently sloping wedge-shaped fan of soil and rock, much of the material eroded from its own drainage as the result of heavy rains. Depending upon the size, extent and gradient of the stream, these mini-deltas can range in size from that of a backyard patio to tracts of several acres.

Although shore views of these features are seasonally obscured by bank vegetation, most locations are linked to higher ground via steep paths used by anglers. In late March, creek mouths large enough to include trees harbor migrating wood ducks.

Because the high-water marks of our rivers consistently document the variety of floatable debris generated by our throwaway culture, views of these beautiful birds are often aesthetically marred by the inclusion of tires, mud-stained blocks of Styrofoam, empty beer cans and all kinds of plastic containers.

Islands are readily defined and delineated by the water surrounding them. In rivers they are anchored by vegetation, built and sculpted into elongate shapes by currents. If identifying islands demands little of us, understanding their innate appeal requires us to consider our exposure to variations of the land form in story, myth and popular culture. For anyone interested in river wildlife, the attraction is easier to explain:

Whether your interests involve fish, fowl or mammals such as muskrats or beavers, the shallow zone where land and water meet is the place to focus your attention.

Where they occur, islands more than double this zone, compressing extra shoreline along their flanks, head and tail. What is effectively a quadrupling of shoreline occurs in a bend of the Allegheny between Penn Hills and Blawnox where the parallel Sycamore Island and Nine Mile Island flank the navigational channel.

Surface winds blowing counter to the direction of river flow give rise to this feature -- the breaking foam-like crests of multiple waves. With occurrences that are fleeting in some seasons and seemingly boundless in others, the term is offered as stand-in for a considerably wider range of surface conditions.

Most lack names, but they have not escaped notice. In the long out-of-print "The Three Rivers" (Pittsburgh History and Landmarks Foundation, 1982), the late Walter Kidney of Pittsburgh History & Landmarks Foundation had this to say about the Ohio, Monongahela, and Allegheny:

"They appear in different colors, and odd textures cover parts of their surfaces, apparently without cause. Sometimes they are slick as wax, sometimes minutely ruffled like a silver-gray felt, sometimes blown into little waves, sometimes marbled with ice. The surface quality of the land changes slowly with the seasons for the most part, but the surface of a river, seen from a hillside, is different from one day to the next."

Looking for more from the Post-Gazette? Join PG+, our members-only web site. You'll get exclusive sports content, opinion, financial information, discounts from retailers and restaurants, and more. Our introduction to PG+ gives you all the details.