A stream table is a scaled, physical model used to study hydrology and fluvial geomorphology. This miniature river system allows scientists and students to observe how flowing water interacts with sediment to shape a landscape in a compressed timeframe. By manipulating variables like the water flow rate and the angle of the slope, observers gain insight into the mechanisms that govern real-world stream and river behavior.
Physical Structure and Key Components
The stream table is typically a long, rectangular flume or trough constructed from waterproof materials like plastic, metal, or wood. The container holds the landscape material, often consisting of fine to medium-grained sand, sometimes mixed with silt or pebbles to simulate natural sediment. The sediment must be loose enough to be moved by water but cohesive enough to hold an initial shape.
A water source, such as a recirculating pump or a gravity-fed reservoir, is positioned at the elevated end to serve as the stream’s headwaters. This inlet controls the rate of water flow into the system, known as the discharge. The table is mounted on supports, like adjustable jack stands, which allow the user to control the gradient or slope. This slope dictates the initial velocity of the water. At the lower end, a drainage system or outlet collects the water and any transported sediment, often leading into a catch basin.
How Water Shapes the Landscape in the Table
The energy of the flowing water is the driving force behind landscape modification. Water flow initiates erosion, which is the detachment and removal of sediment particles from the streambed and banks. This process is most pronounced where water velocity is highest, such as on the outside curves of a developing stream channel or when the table’s gradient is steep.
Once sediment is dislodged, the water carries it downstream through transport. Sediment is carried as a suspended load, floating within the water column, or as a bed load, which rolls, slides, or bounces along the channel floor. The stream’s capacity to transport material is directly related to its velocity; doubling the water’s speed can significantly increase its ability to carry sediment.
As the stream flow slows down—for instance, when the water reaches a flatter section or a wider basin—it loses the energy required to keep the material moving. This reduction in velocity triggers deposition, where the sediment settles out of the water column. Varying the water flow rate or the composition of the sediment allows for the observation of differential deposition, where larger, heavier particles settle first, followed by finer material.
Landforms and Concepts Demonstrated
The interplay of erosion, transport, and deposition rapidly creates recognizable geological features. One common feature is the stream meander, a natural, S-shaped curve that develops as water erodes the outer bank, forming a cutbank. Simultaneously, sediment is deposited on the inner bank to create a point bar. Over time, these meanders migrate across the simulated floodplain.
If the neck of a meander becomes narrow, the stream may cut a new, straighter path during a high-flow event, isolating the old bend to form an oxbow lake. When the stream reaches the flat outlet, its velocity drops sharply, resulting in the rapid deposition of its sediment load. This deposition builds up a fan-shaped landform known as a delta. The table can also demonstrate the formation of alluvial fans where a steep stream abruptly meets a flat valley floor, or a braided stream pattern characterized by multiple, interwoven channels separated by temporary islands of sediment.