Question

How does a braided stream differ from a meandering stream?

Short answer

A braided stream is a network of interconnected channels with a steep gradient, high sediment load, and variable water supply that form due to high sediment supply and variable discharge, often found in mountainous or glacial environments. In contrast, a meandering stream is a single sinuous channel with gentle gradient, low sediment load, stable water supply, and forms due to low sediment supply and constant water flow, typically found in lowland or gently sloping landscapes. The channel bed of a braided stream consists of coarse sediment, while that of a meandering stream consists of fine sediments like sand, silt, and clay.

Step-by-step solution

Define braided streams

A braided stream is a network of interconnected channels that split and merge, forming a branching pattern. Braided streams typically have a steep gradient, a high sediment load, and a variable water supply.

Define meandering streams

A meandering stream is a single sinuous channel with a relatively constant water flow that forms a series of regular bends called meanders. Meandering streams typically have a gentle gradient, low sediment load, and relatively stable water supply.

Discuss channel characteristics

The channel characteristics of braided streams feature multiple channels separated by active or inactive sediment bars, and the channel bed consists of coarse sediment. On the other hand, meandering streams possess a single channel that snakes back and forth across the floodplain over time. The channel bed is usually made of fine sediments like sand, silt, and clay.

Explain the formation processes

Braided streams form when there's a high sediment supply and the river's discharge is highly variable, such as in environments with rapid surface runoff or melting glaciers. This causes the stream to become choked with sediment, forming bars and islands within the channel and forcing the river to split into multiple channels. On the other hand, meandering streams are formed in regions with relatively low sediment supply and a more constant water flow. The channel erosion on the outer banks of curves and deposition on the inner banks lead to the widening and deepening of the meanders, causing the stream to snake through the landscape.

Describe depositional environments

Braided streams are typically found in locations with steep, mountainous terrain where sediment supply is high, and in glacial environments where the melting ice provides significant amounts of sediment and variable water supply. Meandering streams are more common in lowland environments such as plains and gently sloping landscapes, where the stream gradient is low, and the sediment supply and water flow are relatively stable.

Key concepts

Braided Streams

Braided streams are fascinating natural watercourses characterized by a network of interwoven channels. These channels continually split and rejoin in a pattern reminiscent of a braid.
The nature of braided streams results from several factors:

• They usually form in regions with steep gradients, which provide ample energy to transport sediment.
• The sediment load is often high, meaning the stream carries a large amount of rocks and debris.
• The water supply in braided streams is variable, leading to fluctuating flow rates at different times.

Generally, braided streams are found in environments with rapidly changing water dynamics, such as areas near melting glaciers or steep mountainous regions. These streams often display numerous sandy or gravelly bars within their channels, resulting from the deposition of excess sediment.

Meandering Streams

In contrast to braided streams, meandering streams follow a single, curving path through the landscape. These streams twist and turn to form loops known as meanders.
The characteristics that define meandering streams include:

• A gentle slope or gradient, allowing the stream to flow slowly and smoothly.
• A relatively low sediment load, which means less debris carried by the water.
• A stable, continuous flow of water, maintaining a more predictable path.

Meandering streams are typically found in flat, lowland areas such as floodplains. Their constant lateral erosion on outer bends and deposition on inner bends lead to the dynamic shifts in the stream path over time.

Channel Characteristics

Channel characteristics refer to the unique features of a stream's path. For braided streams, the channel is marked by multiple parallel paths separated by bars of sediment that can either be permanent or temporary.
Key features of braided stream channels:

• Coarse sediment composition, often including gravel and stones.
• Repeated division and rejoining of channels.

Conversely, meandering streams have a single, winding channel that traverses the floodplain. The channel bed is smoother and typically composed of finer materials like sand, silt, and clay. These channels are defined by their sinuous curves, making them distinct from the more complex channels of braided streams.

Formation Processes

The formation of each type of stream involves unique processes dictated by environmental conditions.
For braided streams, formation occurs when there's an excess of sediment and highly variable river discharge. Rapid surface runoff or glacier melting often contributes to this variability. The sediment-laden water splits into multiple channels, creating the braided appearance.
In contrast, meandering streams form in areas where water discharge is consistent and sediment supply is lower. Stream bends or meanders develop due to erosion on the outer edges of curves and deposition on the inner edges. This continuous process causes the formation of pronounced bends and loops that define these streams.

Depositional Environments

Different environments facilitate the development of either braided or meandering streams based on sediment supply and gradient.
Braided streams generally occur in:

• Mountainous areas with steep slopes, which provide the gradient needed for swift sediment transport.
• Glacial regions, where melting ice offers a high sediment load and variable water flow.

On the other hand, meandering streams are typically found in environments such as:

• Flat, lowland locations like plains, where the gradient is minimal and steady water flow is present.
• Regions with stable water supply and less variation in sediment influx.

These environments support the distinct features and behaviors of each stream type, shaping the landscape over time.