Unit 5: How do you prepare for floods and landslides?
Students learn about surface processes by exploring flooding and landslides, and how humans design communities to mitigate associated hazards. This makes sense because water, in general, and high-flow events in particular, play a leading role in shaping much of the Earth's surface. Also, flooding is the most commonly encountered natural hazard. Even in deserts, most erosion happens during flash floods, and flash floods claim lives. Off the Earth, many landforms on Mars were sculpted by the water that coursed across that planet's surface billions of years ago, and liquid methane and ethane shape the surface of Titan.
Summary
Students learn about the "where" and "when" of floods and landslides. They explore flooding during the 2017 Hurricane Harvey in Houston, TX, and they apply what they learn to flooding in an area of interest. For landslides, the emphasis is on Southern California, and applying what they learn there. Students learn how to design communities that are more resilient in the face of these hazards. Urban stormwater solutions are emphasized.
Motivating Questions:
- How often do floods happen?
- Where do floods happen?
- How can humans design new urban developments in such a way that flood risk is reduced?
- Where do landslides happen, and how can humans design urban developments in a way that reduces the risk of landslide losses?
Time Needed:
The activities in this unit are designed to take place over the course of five 85-minute class periods. The in-class part of Unit 5.3:Should we rebuild after a disaster? requires only 25 min, but Unit 5.3 pre-class and homework assignments could be completed in class.
Prerequisite Skills:
No hydrologic knowledge is needed before starting this unit. If not completing other units of this course, it is recommended that students have basic Earth processes and resources knowledge and are prepared to analyze and interpret data.
Learning Outcomes
At the end of the unit, students will be able to:
- Use streamflow data and models as evidence to describe the relationship between urbanization and flooding.
- Analyze precipitation and gage data and topographic maps to identify spatial and temporal patterns in the occurrence of flooding and landslides.
- Evaluate ways in which design reduces risk from flooding and landslides.
Overview
Throughout Unit 5, students use science and engineering practices to explore ways to mitigate problems caused by flooding, landslides, and sea level rise. Each part of the unit touches on distinct and generalizable aspects of these hazards, including mitigating actions taken by individuals as well as those implemented collectively by entire communities, engineered and natural solutions, and the difficult decision to either live with a hazard or move away from it. In Unit 5.2: Designing flood-resilient developments, students are given information about the intersection of flooding, ethnicity, and economic status, and they are explicitly asked to consider hazards from multiple perspectives (e.g., parent, developer, scientist) in Unit 5.4: Heavy rainfall and landslides and Unit 5.5: Adapting to sea level rise.
Geographically, most of the unit focuses on the greater Houston, TX, area, creating synergy between different parts of the unit, and providing the opportunity to connect the unit with information about hurricanes and climate change. Unit 5.2: Designing flood-resilient developments is in many ways the "guts" of Unit 5, touching on a variety of topics including hydrographs, flood frequency, floodplain maps, and flood-resistant design. Unit 5.3: Scientist Profile Homework features an entry-level hydrology technician who learned about geoscience careers at a community college.
Although much of Unit 5 is centered on Houston, TX, and high rainfall events, parts of the unit make other connections to broaden knowledge, discourage misconceptions, or both. For example, Unit 5.4: Heavy rainfall and landslides broadens knowledge by focusing on southern California debris flows because these important phenomena are not common on the Gulf Coast. Examples of content added to both broaden knowledge and discourage misconceptions include information about the role of snow in the hydrologic cycle of the northern United States (Unit 5.2 Teaching Tip Slide), drought (Unit 5.2 In-Class Activity B Slide Set), and earthquake-triggered landslides (Unit 5.4 In-Class Activity).
Unit 5.1: Introduction to flooding and the water cycle (~60 min of class time). Students learn about flooding in relation to the water cycle. They search for information about flooding in an area of personal interest, and they consider the accuracy, trustworthiness, and relevance of information they obtain from the internet and other sources. Students examine stormwater management solutions to flooding in urban areas. An integral pre-class assignment requires ~75 min, and an optional homework assignment requires ~60 min.
Unit 5.2: Designing flood-resilient developments (~75 min of class time). Students use stream gage and precipitation data and maps to explore flood hazards, and design a community where the risk of flooding is reduced. They explore the meaning of "100-year flood", while constructing a flood frequency graph. In addition, students learn about online floodplain maps and topographic profiles. Geographically, students focus on Houston, TX, and an area of personal interest. An integral pre-class assignment requires ~20 min, and an optional homework assignment requires ~60 min.
Unit 5.3: Should we rebuild after a disaster? (~25 min of class time). Students consider whether or not to repair and reoccupy a landslide-damaged apartment building at a specific site on Lake Granbury, TX. To inform their decision, they examine a landslide at the site. Before coming to class, they watch news videos. Then, they come to class and assemble in groups of 3-5. During a single class period, each group considers precipitation and lake level data based on what they learned before coming to class. They use all of this information to form ideas about why the landslide happened. For homework, they use Google Earth imagery to examine how land use changed near the lake after the landslide. Was the apartment building repaired and reoccupied? Does the student think the correct decision was made? Why or why not? An integral pre-class assignment requires ~20 min, and an optional homework assignment requires ~15 min. There is also an optional ~15 min profile of an entry-level hydrologic technician who became interested in hydrology at a community college.
Unit 5.4: Heavy rainfall and landslides (~60 min of class time). Students examine landslide hazards in mountainous parts of Southern California and adjoining valleys. Students assume various roles (e.g., school superintendent) and use online maps to explore hazards. They examine the landslide problems from different perspectives, and they apply what they have learned to their areas of interest. An integral pre-class assignment requires ~45 min, and an optional homework assignment requires ~30 min.
Unit 5.5: Adapting to sea level rise (~75 min of class time). Students explore sea level rise scenarios, learn about a range of "hard" and "soft" engineered solutions, and ponder managed retreat from the coastline. An integral pre-class assignment requires ~60 min, and a recommended homework reflection over the entire unit (exit ticket) requires ~15 min.