GEOG 1301 Ch 13 Lecture #1

Summary

In this lecture, Dr. Jaegar introduces the concept of fluvial processes, explaining how streams and rivers, from the smallest creeks to massive rivers like the Mississippi, shape landscapes. He covers key concepts like overland flow and stream flow, emphasizing the rule that water always flows downhill. The discussion also explores drainage basins, watersheds, and stream ordering, illustrating how smaller streams combine to form larger ones, eventually leading to significant rivers. Dr. Jaegar ties these concepts to the San Antonio area, explaining how water flows through different watersheds and contributes to larger river systems such as the Mississippi River.

Takeaways

• 😀 Streams refer to any flowing body of water, from small creeks to large rivers like the Mississippi or Rio Grande.
• 🌍 Fluvial processes describe how streams and rivers shape the land through their movement and the water they carry.
• 💧 Overland flow occurs when water moves across the land surface before reaching a stream, while stream flow happens when water is in a stream.
• 🌊 Water always flows downhill due to gravity—this is the key rule in fluvial processes.
• ⛰️ Water flows until it reaches the sea or a basin where it can no longer flow downhill.
• 🌄 The landscape is divided into high areas (interfluves) and low areas (valleys), and water flows from high to low.
• 🏞️ A watershed is a drainage area where all water flows into a single stream or river.
• 📍 In San Antonio, there are several watersheds, including the Medina River and Leon Creek watersheds, which feed into the San Antonio River.
• 🌐 Watersheds can be part of larger, regional watersheds, like the San Antonio River being part of the Guadalupe River watershed.
• 📈 Streams are categorized by 'order,' with first-order streams being the smallest and larger streams having higher orders (e.g., the Mississippi River would be a very high-order stream).
• 🔢 The higher the stream order, the fewer the number of streams at that order, but these streams carry more water.

Q & A

What is the definition of a stream in physical geography?

In physical geography, the term 'stream' refers to any channel or flow of water, ranging from the largest rivers like the Mississippi to the smallest creeks or arroyos that only fill up after rainfall.

What are fluvial processes?

Fluvial processes are the ways in which streams shape and impact their surroundings, including the movement of water across the land and the transformation of landforms.

What is the first rule of fluvial processes?

The first rule of fluvial processes is that water always goes down due to gravity. Water cannot flow upward naturally unless artificially pumped.

What are the two general types of fluvial processes discussed in the chapter?

The two main types of fluvial processes are overland flow (where water moves across the land before reaching a stream) and stream flow (where water moves within a stream, shaping the land around it).

What is overland flow?

Overland flow occurs when raindrops move across the surface of a hill or land area before reaching a stream. It is the first stage in the movement of water across the land.

What are valleys and interfluves?

Valleys are low areas between higher ground, and interfluves are higher areas of land that separate different valleys. These areas help organize the flow of water within a watershed.

What is a watershed?

A watershed is an area of land where all the water that falls within it flows out through a single stream or river. It is often described as an area with one 'outlet' for water.

What happens when two streams of the same order combine?

When two streams of the same order combine, they form a stream of the next order. For example, two first-order streams combine to form a second-order stream, two second-order streams form a third-order stream, and so on.

How does stream order affect the size of streams in a watershed?

As the stream order increases, the size and flow of the stream also increase. First-order streams are small and numerous, while higher-order streams like fourth-order streams are fewer but much larger and carry more water.

How does the San Antonio area relate to the concept of watersheds?

The San Antonio area is located at the boundary of multiple watersheds. For example, the Medina River watershed and Leon Creek watershed are both part of the larger San Antonio River watershed. Water in the area flows through these networks to eventually reach the Gulf of Mexico.