A drop of water falling on the boundary between the Capilano and Seymour drainage basins a. The pattern of tributaries within a drainage basin depends largely on the type of rock beneath, and on structures within that rock folds, fractures, faults, etc. The three main types of drainage patterns are illustrated in Figure 3.
Dendritic patterns, which are by far the most common, develop in areas where the rock or unconsolidated material beneath the stream has no particular fabric or structure and can be eroded equally easily in all directions. Examples would be granite, gneiss, volcanic rock, and sedimentary rock that has not been folded. Most areas of British Columbia have dendritic patterns, as do most areas of the prairies and the Canadian Shield. Trellis drainage patterns typically develop where sedimentary rocks have been folded or tilted and then eroded to varying degrees depending on their strength.
The Rocky Mountains of B. Rectangular patterns develop in areas that have very little topography and a system of bedding planes, fractures, or faults that form a rectangular network. Rectangular drainage patterns are rare in Canada. Figure 3. Typical dendritic, trellis, and rectangular stream drainage patterns. In many parts of Canada, especially relatively flat areas with thick glacial sediments, and throughout much of Canadian Shield in eastern and central Canada, drainage patterns are chaotic, or what is known as deranged Figure 4, left.
Lakes and wetlands are common in this type of environment. A fourth type of drainage pattern, which is not specific to a drainage basin, is known as radial Figure 4, right. Radial patterns form around isolated mountains such as volcanoes or hills, and the individual streams typically have dendritic drainage patterns. Figure 4. Left: a typical deranged pattern; right: a typical radial drainage pattern developed around a mountain or hill.
Over geological time, a stream will erode its drainage basin into a smooth profile similar to that shown in Figure 5. If we compare this with an ungraded stream like Cawston Creek Figure 1 , we can see that graded streams are steepest in their headwaters and their gradient gradually decreases toward their mouths.
Ungraded streams have steep sections at various points, and typically have rapids and waterfalls at numerous locations along their lengths. Figure 6. An example of a change in the base level of a small stream that flows into the Similkameen river near Keremeos. The previous base level was near the top of the sandy bank. The current base level is the river. A graded stream can become ungraded if there is renewed tectonic uplift, or if there is a change in the base level, either because of tectonic uplift or some other reason.
As stated earlier, the base level of Cawston Creek is defined by the level of the Similkameen River, but this can change, and has done so in the past.
Figure 6 shows the valley of the Similkameen River in the Keremeos area. Vegetation and land use affect the amount of water reaching the river channel. Evaporation and transpiration from vegetation evapotranspiration return moisture to the atmosphere, while uptake of water and anchoring of soil by vegetation can reduce surface water runoff and erosion, respectively.
Human Influences. Water diversions, withdrawals and discharges are potential human influences that can affect the water balance of a drainage basin. Features such as dams affect the natural flow regime of a river, resulting in changes to both the seasonal and yearly variations in water flow.
Human impacts on vegetative cover and land use within the drainage basin can affect infiltration and runoff patterns. Athabasca Drainage Basin. Monitoring locations map Food web Fish catalogue Stream flow hydrographs browse all Send us Feedback: send a general website comment report a specific problem with this page. Athabasca Drainage Basin Source: Wikipedia click to enlarge. There are 7, unique basin numbers, and length of the number can be up to 13 characters long, depending on stream order of the basin.
The first digit column 1 designates the major basin, the first two digits columns designate the regional basin, the first 4 digits columns designate the subregional basin, and the first seven digits columns designate the local basin. The basin number includes a few codes at the end. The letter L for lake denotes a reach-impoundment identifier for an impoundment basin and is followed by the reach-impoundment number. The letter R for reach denotes a reach-impoundment identifier for a stream reach basin and is followed by the reach-impoundment number.
A drainage basin is an area of land where water from rain or snow melt drains downhill into a body of water such as a river, lake, wetland or ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surface from which water drains into those channels. Used as the basis for DEP drainage basin mapping, a natural drainage basin is one in which the outlet point is a natural occurring feature. These outlet points occur at stream confluences, stream outfalls into waterbodies, and impoundments.
The hierarchical system of drainage basin delineation and numbering, as implemented by DEP, allow for the association of the physical resources to the naturally occuring drainage system that covers Connecticut.
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