13: Flooding

Last updated
Save as PDF

Page ID: 25493

$ \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } $

$ \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} $

$ \newcommand{\id}{\mathrm{id}}$ $ \newcommand{\Span}{\mathrm{span}}$

( \newcommand{\kernel}{\mathrm{null}\,}\) $ \newcommand{\range}{\mathrm{range}\,}$

$ \newcommand{\RealPart}{\mathrm{Re}}$ $ \newcommand{\ImaginaryPart}{\mathrm{Im}}$

$ \newcommand{\Argument}{\mathrm{Arg}}$ $ \newcommand{\norm}[1]{\| #1 \|}$

$ \newcommand{\inner}[2]{\langle #1, #2 \rangle}$

$ \newcommand{\Span}{\mathrm{span}}$

$ \newcommand{\id}{\mathrm{id}}$

$ \newcommand{\Span}{\mathrm{span}}$

$ \newcommand{\kernel}{\mathrm{null}\,}$

$ \newcommand{\range}{\mathrm{range}\,}$

$ \newcommand{\RealPart}{\mathrm{Re}}$

$ \newcommand{\ImaginaryPart}{\mathrm{Im}}$

$ \newcommand{\Argument}{\mathrm{Arg}}$

$ \newcommand{\norm}[1]{\| #1 \|}$

$ \newcommand{\inner}[2]{\langle #1, #2 \rangle}$

$ \newcommand{\Span}{\mathrm{span}}$ $ \newcommand{\AA}{\unicode[.8,0]{x212B}}$

$ \newcommand{\vectorA}[1]{\vec{#1}} % arrow$

$ \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow$

$ \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } $

$ \newcommand{\vectorC}[1]{\textbf{#1}} $

$ \newcommand{\vectorD}[1]{\overrightarrow{#1}} $

$ \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} $

$ \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} $

$ \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } $

$ \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} $

$\newcommand{\avec}{\mathbf a}$ $\newcommand{\bvec}{\mathbf b}$ $\newcommand{\cvec}{\mathbf c}$ $\newcommand{\dvec}{\mathbf d}$ $\newcommand{\dtil}{\widetilde{\mathbf d}}$ $\newcommand{\evec}{\mathbf e}$ $\newcommand{\fvec}{\mathbf f}$ $\newcommand{\nvec}{\mathbf n}$ $\newcommand{\pvec}{\mathbf p}$ $\newcommand{\qvec}{\mathbf q}$ $\newcommand{\svec}{\mathbf s}$ $\newcommand{\tvec}{\mathbf t}$ $\newcommand{\uvec}{\mathbf u}$ $\newcommand{\vvec}{\mathbf v}$ $\newcommand{\wvec}{\mathbf w}$ $\newcommand{\xvec}{\mathbf x}$ $\newcommand{\yvec}{\mathbf y}$ $\newcommand{\zvec}{\mathbf z}$ $\newcommand{\rvec}{\mathbf r}$ $\newcommand{\mvec}{\mathbf m}$ $\newcommand{\zerovec}{\mathbf 0}$ $\newcommand{\onevec}{\mathbf 1}$ $\newcommand{\real}{\mathbb R}$ $\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}$ $\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}$ $\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}$ $\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}$ $\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}$ $\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}$ $\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}$ $\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}$ $\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}$ $\newcommand{\laspan}[1]{\text{Span}\{#1\}}$ $\newcommand{\bcal}{\cal B}$ $\newcommand{\ccal}{\cal C}$ $\newcommand{\scal}{\cal S}$ $\newcommand{\wcal}{\cal W}$ $\newcommand{\ecal}{\cal E}$ $\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}$ $\newcommand{\gray}[1]{\color{gray}{#1}}$ $\newcommand{\lgray}[1]{\color{lightgray}{#1}}$ $\newcommand{\rank}{\operatorname{rank}}$ $\newcommand{\row}{\text{Row}}$ $\newcommand{\col}{\text{Col}}$ $\renewcommand{\row}{\text{Row}}$ $\newcommand{\nul}{\text{Nul}}$ $\newcommand{\var}{\text{Var}}$ $\newcommand{\corr}{\text{corr}}$ $\newcommand{\len}[1]{\left|#1\right|}$ $\newcommand{\bbar}{\overline{\bvec}}$ $\newcommand{\bhat}{\widehat{\bvec}}$ $\newcommand{\bperp}{\bvec^\perp}$ $\newcommand{\xhat}{\widehat{\xvec}}$ $\newcommand{\vhat}{\widehat{\vvec}}$ $\newcommand{\uhat}{\widehat{\uvec}}$ $\newcommand{\what}{\widehat{\wvec}}$ $\newcommand{\Sighat}{\widehat{\Sigma}}$ $\newcommand{\lt}{<}$ $\newcommand{\gt}{>}$ $\newcommand{\amp}{&}$ $\definecolor{fillinmathshade}{gray}{0.9}$

Learning Objectives

After reading this chapter, completing the exercises within it, and answering the questions at the end, you should be able to:

Explain why flooding has been, and remains, an important benefit to human civilizations,
Describe some of the phenomena that cause flooding,
Explain how rain or snowmelt water gets into a stream,
Describe the relationship between the level of the water table and stream discharge,
List some examples of flooding caused by storms, snow melt and slope failures,
Explain how changes made to stream channels can make flooding worse, and
Describe some of the steps we can take to reduce the risks of flooding and the damage caused by flooding.

13.1: Factors that Control Stream Discharge and Flooding
This page discusses flooding, which occurs when water exceeds a stream's capacity due to heavy rainfall and snowmelt. It details stream flow sources like overland flow and groundwater discharge, exemplified by the fluctuating discharge of the Little Qualicum River in 1986. Additionally, flooding can result from slope failures or blockages. When streams reach bank-full, flow velocity drops, causing sediment deposition that forms levees, offering some protection but potentially prolonging flooding.
13.2: Examples of Flooding Events
This page discusses severe flooding events, highlighting Hurricane Harvey in August 2017 as the wettest tropical storm in U.S. history, causing over $125 billion in damages and over 100 fatalities. It also mentions the June 2013 flooding in Alberta, costing around $5 billion. Climate changes are increasing flooding risks, and predicting such events relies on historical data, though shifting climate conditions could impact future probabilities.
13.3: Managing Floods and Limiting Flood Damage
This page discusses the implementation of significant flood control measures, including levee construction, which revealed the complexities of managing flood risks. Strategies that blend natural and engineered solutions, such as enhancing green spaces and improving drainage, are vital. Major changes along the Red River in North Dakota resulted in the Greenway, which features parks and recreational areas.
13.4: Flooding and Earth Systems
This page discusses the ecological and geological significance of river flooding, highlighting its role in forming floodplains that benefit ecosystems and agriculture, the deposition of valuable sedimentary rocks, and the transport of sediments offshore. It mentions the January 2020 turbidity flow from the Congo River as an example, demonstrating how river flooding affects undersea geology by moving sediments over 1200 km after a major flood.
13.5: Chapter 13 Summary and Questions for Review
This page covers Chapter 13, which focuses on flooding factors, predominantly heavy rainfall and rapid snowmelt. It uses Hurricane Harvey as a case study and addresses climate change's role in future flooding. The chapter stresses infiltration's importance for flood management and discusses engineering solutions, such as dams, which may have drawbacks. Additionally, flooding contributes to Earth's systems by forming fertile plains and moving sediments.

The River Nile defines a green swath across the otherwise arid Sahara Desert, (Figure $\PageIndex{1}$) and for thousands of years the Nile has been the lifeblood for humans in that region. For most of that time farming was timed by the annual late summer floods that originated with intense monsoon rains in the highlands of Ethiopia. Those floods inundated the area for several kilometres on either side of the river, as well as much of the delta. Each year when the floods receded the soil was saturated with water and covered with a layer of fertile silt. The crops planted after the flood grew vigorously, and when harvested a few months later, would feed the population until the next summer—unless the flood was small or didn’t come at all. Although there were famine years, flooding of the Nile was sufficiently reliable that the river has supported a population of several million since about 1500 BCE.

Figure $\PageIndex{1}$ The River Nile and Delta in Egypt

The lower Nile doesn’t flood any more because the floodwaters are captured by the High Aswan Dam, but Egypt now has a well-developed irrigation system to distribute Nile water to its agricultural regions.

Floods adjacent to rivers and on deltas have created and maintained the relatively flat and fertile land that most people in the world live on or close to, and, as in Egypt, floodplains are where our agricultural ancestors first made their living. But while flooding has always benefited us, it is increasingly becoming a problem because, instead of living with floods, we have chosen to fight against them. We have occupied the world’s floodplains and filled them with buildings and transportation infrastructure so that when floods happen—as they always will—it costs us dearly. As shown on Figure $\PageIndex{2}$ the global economic costs of flooding have increased dramatically in recent decades. Over the time period shown, flooding represented almost 30% of the costs of all natural disasters, second only to extreme weather events (many of which caused floods). Part of the increase in the cost of floods may be a result climate change, but much of it is because there are so many more of us living on floodplains, because we have tried to control rivers, and because our infrastructure is now much more expensive.

Figure $\PageIndex{2}$: The Global Annual Direct Economic Costs of Flooding, 1965 to 2018

This chapter is only about river flooding. Coastal flooding related to storms, and from climate-change sea-level rise are covered in Chapter 15.

Media Attributions

Figure 13.0.1 Egypt, NASA, public domain, via Wikimedia Commons, https://commons.wikimedia.org/wiki/F...635018418).jpg
Figure 13.0.2 Steven Earle, CC BY 4.0, using data from EMDAT, 2020, OFDA/CRED International Disaster Database, Université catholique de Louvain – Brussels – Belgium, https://ourworldindata.org/grapher/d...ral-disasters/

Search

Text Color

Text Size

Margin Size

Font Type