FLUVIAL PROCESSES AND LANDSCAPES

Note: Please refer to the GETTING STARTEDmodule to learn how to maneuver through, and how to answer the lab questions, in the Google Earth () component.

KEY TERMS

You should know and understand the following terms:

Alluvial fan

Drainage divide

Oxbow Lake

Basin

Drainage pattern

Sinuosity

Braided streams

Entrenched meander

Stream discharge

Cutbanks

Hydrograph

Stream order

Delta

Meandering river

Watershed

Drainage density

Meander scar

LAB LEARNING OBJECTIVES

After successfully completing this module, you should be able to do the following tasks:

· Describe the concepts of sub-basins and watersheds

· Identify different human water uses of a river

· Construct a stream order for a river system

· Compute drainage density of a given basin

· Identify drainage patterns of river networks

· Explain how braided rivers and meandering rivers are formed

· Identify the physical features common to a meandering river system

· Describe the physical conditions necessary to form alluvial fans

INTRODUCTION

This module examines fluvial processes and landscapes. Topics include watersheds, drainage patterns and densities, stream order, meandering and braided streams, and alluvial fans. While these topics may appear to be disparate, you will learn how they are inherently related. The modules start with four opening topics, or vignettes, which are found in the accompanying Google Earth file. These vignettes introduce basic concepts of fluvial processes and landscapes. Some of the vignettes have animations, videos, or short articles that will provide another perspective or visual explanation for the topic at hand. After reading the vignette and associated links, answer the following questions. Please note that some links might take a while to download based on your Internet speed.

Expandthe INTRODUCTION folder and then select Topic 1: Introduction

Read Topic 1: Introduction

Question 1: Which of the following is a reason for the location selected for the first English settlement in the New World, Jamestown, VA?

A. Prime agricultural land

B. On the advice from the Native Americans

C. Deep water port

D. The land was already cleared

Read Topic 2: Rivers of Life

Question 2: If our ability to predict floods has improved significantly, why does economic loss continue to rise? (Check all that apply).

A. Increased urbanization

B. Increased population

C. Increased development along coasts

D. Increased real estate values

Read Topic 3: Rivers of Waste

Question 3: What are potential outcomes or conditions resulting from too much nitrogen running off from agricultural fields? (Check all that apply).

A. Eutrophication of water bodies

B. Decrease in crop production

C. Contamination of groundwater

D. Health issues in infants

Read Topic 4: Erosion

Question 4: List three ways in which humans contribute to stream bank erosion.

A. Vegetation removal

B. Increase in impervious surfaces

C. Wave from boats

D. Wind action on exposed banks

Read Topic 5: Transportation and Deposition

Question 5: What impacts do dams have on the transportation of sediment? Check all that apply.

A. Decrease in sediment transportation upstream from dam

B. Increase in sediment transportation downstream from dam

C. Decrease in sediment transportation downstream from dam

D. Increase in sediment transportation upstream from dam

Collapse and uncheckthe INTRODUCTION folder

For the remaining portions of this module, you will identify and explain the geographic distribution, patterns, and processes associated with fluvial environments. In doing so, you will recognize and appreciate the impact of rivers.

GLOBAL PERSPECTIVE

Expand the GLOBAL PERSPECTIVE folder and then expand the World Rivers folder. Double‑click and select any continent or world region. To display river information (name and approximate length) click any river in the Google Earth 3-D pane.

Collapse the World Rivers folder.

Major Cities on Rivers

Expand Major Cities on Rivers.

For each question below, type the latitude and longitude coordinates into the Search field and then press Enter. When you arrive at your destination, find the information that you will use to fill in the blanks below:

Question 6: 33 18 59 N, 44 23 33 E

City:

A. Atlanta

B. Baghdad

C. Cairo

D. Dusseldorf

River:

A. Mississippi

B. Euphrates

C. Tigris

D. Nile

Question 7: 30 03 29 N, 31 14 05 E

City :

A. Paris

B. Moscow

C. Cairo

D. Shanghai

River:

A. Ohio

B. Jordan

C. Zambesi

D. Nile

Question 8: 48 51 26 N, 2 21 04 E

City:

A. London

B. Madrid

C. Paris

D. Buenos Aires

River:

A. Rio de la Plata

B. Seine

C. Thames

D. Volga

Question 9:Montreal, Canada.

Latitude: A. 45° 30’S B. 73° 33’N C. 45° 30’N D. 73° 33’S

Longitude: A. 45° 30’E B. 73° 33’N C. 45° 30’S D. 73° 33’W

River:

A. Montreal

B. St. Lawrence

C. Hudson

D. Ottawa

Collapse anduncheck the GLOBAL PERSPECTIVE folder

WATERSHEDS AND DRAINAGE DENSITY

Expand the WATERSHEDS AND DRAINAGE DENSITY folder.

A drainage basin is an area of land in which a stream receives water, predominately by surface runoff, through flow, and groundwater flow. Drainage basins are topographically divided from each other by the highest points of elevation, so that all water from the ridges and hills flow into a given drainage basin and thereby into a given stream. This topographic delineation is commonly referred to as a watershed (the drainage divide between two drainage areas), although many in the United States use the term watershed interchangeably with drainage basin or catchment.

A large drainage basin can contain several smaller drainage basins or sub-basins. The nested nature of these sub-basins is determined by topography as well as where the water flows out of the drainage area, known as the outflow point.

In Figure 1, dash-lines A, B, and C demarcate the watersheds of the tributary streams, while dash-line D delineates the watershed of a larger drainage basin for the larger streams, which includes the smaller tributaries and their sub-basins.

Figure 1. Watershed map (Source: Maidstone Lake USGS 7.5 minute map).

Understanding watersheds are important because stream flow and water quality are influenced by the nature of and changes in the drainage basin. We can determine what is happening in our river basins by examining the water flow and water quality from a river’s outflow point. Changes to water flow or water quality in rivers could be due to either natural events (such as lightning induced forest fires increasing soil erosion) or human modifications (such as agricultural practices increasing pollution).

Double-click and select Columbia River Watershed.

The Columbia River watershed encompasses 258,000 square miles (approximately the size of France), with 220,000 square miles in the U.S. and 38,000 square miles in Canada. The length of the river is approximately 1243 miles, making it the 15th longest river in the United States.

Uncheck Columbia River Watershed.

Check the Columbia River Sub-basin US only folder. Click on each sub-basin in the Google Earth map pane to identify its name.