“Cryin’ won’t help you, prayin’ won’t do you no good.[i]”

In this entry, I take us back to Floodtown and conclude my series on the use of “stories” in planning for climate change.

Floodtown is an imaginary place in the Detroit Metro Area on the Detroit River. For the last 15 years, it has experienced recurrent, record floods that seem a part of the warming climate. The floods cause property damage and challenge the community’s ability to develop and attract people and businesses.

Floodtown’s residents want to find ways to manage increasing amounts of water as Earth continues to warm.

Don’t forget to look around

One of the tools I’ve proposed to plan for climate change is to look around at the surface. We started Floodtown’s story by placing it in the context of the Great Lakes, from Lake Superior to the Atlantic Ocean. Now let’s look at the local surface in our fair city. We ask: Why does Floodtown flood, and why is the flooding getting worse?

Floodtown was built in a low-lying area more than a century ago. Considered useless swampland, developers drained the swamp to make the land useful. They dug ditches, added fill, and diverted creeks into the Detroit River. As the ditches were built, some were envisioned as canals that allowed residents to dock boats and have access to the river and lakes. These canals have become part of the community’s culture; they create a unique sense of place.

Away from the coastline, other communities diverted and filled in inland creeks that used to drain into the swamp and river. Some creeks were piped underground, and people forgot about them. The alterations to creek beds and subsequent building hardened the surface and increased runoff.

Already prone to being wet, Floodtown’s problems were amplified by its shortsighted neighbors. These often-affluent communities saw water as something to get rid of and directed their pipes and culverts toward Floodtown’s canals. Land-use decisions made in these upstream communities occurred in different jurisdictions, with different conditions and objectives. Downstream consequences were given low priority.

Once the water was gone, the upstream communities were happy. The downstream community, Floodtown, was not.

The situation described here is common in the Great Lakes region and across the United States. Land-use decisions, the built environment, and engineered infrastructure have created or amplified flooding risk. One community floods another community. Those skeptical of climate change attribute the increase in flooding to building practices and unmaintained infrastructure.

There is truth to the assertion that how we design, build, and maintain infrastructure is often central to recurrent flooding problems. Any time we become dependent on maintaining levees, pipes, drains, and pumps, we exacerbate our own vulnerabilities. More than 100 years’ worth of silt, tree roots, and material degradation are hard at work destroying Floodtown’s infrastructure.

Also, in those 100 years, it has gotten warmer, extreme precipitation is increasing, and there have been times of persistent, record-high water levels in the Great Lakes and the Detroit River. Climate change is a bump up to pre-existing conditions. The devices, protocols, and procedures to manage the historical problems no longer suffice.

Every real-world “climate change” problem in which I have participated shares one characteristic: Whatever the consequences of climate change, other contributing factors exist. Climate change is not the singularly important issue in the mix. It is, however, often the motivator to address a situation destined to get worse.

Climate change in 2024 tells us it is not in our best interest to keep rebuilding in the same places in the same ways. We cannot simply protect and persist, which is a common human reaction. We have to rethink land-use decisions and the design and implementation of built infrastructure. Plausible stories about real places help us decide what to do.

Types of floods

There are many ways that weather and surface conditions align and lead to flooding.

We instinctively think of intense rainstorms, such as the one that contributed to the Midland, Mich., dam failure in 2020. This instantaneous effect of the storm represents an important scenario, but other things are happening in Floodtown.

From 2017-20, Floodtown experienced very high levels of the Detroit River. When lake levels are high, there is coastal flooding and erosion. However, the Detroit River is not a typical flowing river swelled by local rainfall. It is part of the system that connects Lake Huron to Lake Erie. Persistently high river levels are related to water accumulation over many months and a large region.

Accumulating water also impacts land conditions. If the ground is saturated, it does not take a record-breaking storm to make a flood. Plus, the saturated ground creates instability on the surface. That large tree’s roots next to that critical power line could create problems. Indeed, building foundations and infrastructure likely were not designed or engineered for chronically saturated ground.

Finally, and often ignored, is groundwater and the water table. That is, how far does one have to penetrate the surface to access liquid water? With the accumulation of water due to precipitation and the persistent high water levels in the Great Lakes, the potential of flooding from below needs to be considered.

Floodtown has all these problems.

Focusing on climate

Based on our analysis so far, we know we need to consider water management infrastructure and policy. What is going on in communities outside of Floodtown? Should we build and/or rebuild? If so, where? And how? Should we move communities?

A warming climate motivates these difficult decisions. So, how do we think about weather and climate?

An important early step is to determine the planning horizon. I will choose 50 years because this is an amount of time that we have some experience planning for. We expect buildings and infrastructure to last at least 50 years. It aligns with people’s careers and what we can envision.

We used to be able to assume the climate would not change much over 50 years. We no longer have that luxury. We can measure important changes to the climate from one 10-year time span to the next. This will not have stabilized in 50 years.

We have set building codes, engineering standards, and zoning rules based on historically stable weather and climate. The weather files previously and currently used for design no longer represent the averages and extremes in which we live. The weather 50 years from now will be even further outside the range of that historical experience.

This changing, “nonstationary” climate provides challenges we do not know how to manage. Details we want to know with some degree of certainty are unknowable.

Therefore, we focus on strategic approaches that bring enough flexibility to address the wide range of climate outcomes we are bound to experience.

We know that temperature is going up. What we want to know, next, is how precipitation and evaporation will change. Will this lead to conditions of water abundance or scarcity – or perhaps both – as we swing from one to another?

Conditions to consider

I posed a set of tools throughout this series to help us answer these questions. Let’s apply them as we think about Floodtown.

• Condition: Is water available from the surface to supply the atmosphere with water vapor for precipitation?
• Condition: Are there changes in whether or not it is above or below freezing at the surface?
• Condition: Is there a temperature at which it gets warm enough that we see a transition from ‘it rains more’ to ‘it evaporates more?’
• Are we concerned about the immediate effects of severe storms? What types of storms are important?
• Are we concerned about the accumulating effects of wetness or dryness?
• What are the surface conditions?
• How are “edges” changing?
• How are patterns that organize weather changing?

I will start by analyzing the conditions in the list above.

Condition: Is water available from the surface to supply the atmosphere with water vapor for precipitation?

In general, Floodtown’s region has an ample supply of water vapor for the atmosphere. Though lake effect precipitation is important to the area, Floodtown experiences little direct influence from the lake effect. Much of the water that brings rain to Floodtown comes from far away — the Gulf of Mexico and, perhaps, the heavily irrigated ground of the Corn Belt. At times, water vapor from the Atlantic Ocean is important. Given the importance of the Gulf of Mexico and Atlantic moisture to the region, we proceed knowing plenty of moisture is available, and those sources of moisture are getting warmer.

Condition: Are there changes in whether or not it is above or below freezing at the surface?

The temperature has been rising fastest in the winter, and freezing temperatures are less common. Because of the complicated relationships between water vapor, liquid water, ice, and snow near the freezing point, this will significantly impact frozen precipitation.

Condition: Is there a temperature at which it gets warm enough that we see a transition from ‘it rains more’ to ‘it evaporates more?’

Historically, there have been spans of multiple years when water levels in the Great Lakes have declined because evaporation outpaces precipitation. We expect such behavior in the future, which will quickly drive down lake levels and lead to drought on land.

Stormy weather

Next, I will limit the planning to two types of storms. The first type is the severe summer thunderstorm, most responsible for flash floods. The second type is the middle latitude cyclone, common in winter and responsible for regional snow and winter rain. The middle latitude cyclone is also common in fall and spring. For both types of storms, water vapor transport from the Gulf of Mexico is frequently responsible for extreme events. We already observe increasing intensity and amounts of precipitation, which is all we need to know for now.

How can we decide how much precipitation will increase in these storms? Temperature increase is one of the strongest physical constraints useful for planning. For each degree centigrade that temperature increases there is a 7% increase in the holding capacity for water in the atmosphere. Current model and observational studies suggest that the increase in precipitation per degree centigrade is greater than 7%. We will use 14%.

With the projected rise in temperature in the next 50 years, we expect precipitation increases to be larger than those observed in the past 50 years.

Four scenarios to consider 

The history and geographical details of Floodtown suggest four flooding scenarios to help us think through the effects on the community and the consequences of different responses.

• Immediate effects of a severe rainstorm

Floodtown’s region has seen numerous record thunderstorms that have caused infrastructure failure and flood-related deaths. Planning should account for more frequent storms consistent with the most extreme storms of the last 30 years. In addition, we should expect storms that exceed these extremes. It is reasonable to plan for storms that exceed 50% of the rainfall of the most extreme storm currently on record. Floodtown itself is relatively flat and low-lying. Most severe effects are likely from runoff generated by surrounding communities.

• Persistent wetness: Changes in winter and seasonal runoff

A robust signal of climate change is that winter is getting warmer. When a persistent weather pattern brings moisture into the Great Lakes region, we should expect more precipitation in winter. This is also true for spring and fall. Of particular importance are storm tracks that bring parades of wet storms. We have had such patterns in the past and should expect them in the future. Predictions of pattern shifts in global climate models are more robust than predictions of changes in the characteristics of individual storms. With it getting warmer, we expect less persistent snow cover, melting snow, and rain-on-snow events. Winter flooding becomes more likely. Spring runoff occurs earlier in the year. The ground becomes saturated for more extended periods. Persistent wet ground amplifies the flooding potential of spring rains.

• Persistent high lake and river levels

It takes persistent, regional accumulation of water to raise the levels of the Great Lakes and the Detroit River. Conditions like the persistent wetness scenario above are conducive to raising water levels in spring and early summer. If followed by a wet summer and a second winter of flooding, water level increases can be sustained for longer periods. Cold air outbreaks, though expected to become rarer and more ephemeral, will occur and freeze the lakes, reducing evaporation and forcing a rise in lake levels. High lake levels have a different effect on Floodtown than severe rainstorms. They contribute to coastal erosion and flooding, including the banks of the canals. High lake and river levels do not require rain in Floodtown. The levels could result from persistent regional precipitation that affects the upstream lakes. The adaptation strategies to manage coastal flooding could work at cross purposes with those to manage flooding from severe rainstorms.

• Compound events: A severe rainstorm on saturated ground when lake levels are high.

A compound event has multiple sources of flooding. If persistently high lake levels last months, perhaps years, then it is quite likely that a severe rainstorm will coincide with them. This could lead to a situation where flood mitigation strategies for different types of floods work against each other. We should consider creating sites to store excess water, at least temporarily.

That’s a wrap

I started this series motivated by how I could help a mayor consider adapting to climate change. I developed a set of rules and tools to provide a defensible, plausible approach to realistic stories that could help with planning and design. I have used all of the rules and tools to develop these stories.

These stories are just the beginning. There is still much to be done to evaluate how the different scenarios would interact with existing surface conditions and proposed solutions. Solutions need to be developed by the community in concert with experts in many fields. Solutions need to be creative, and they need to be adaptive, because the climate does not stop changing in 50 years.

One point is clear: A mayor must activate every part of the city government and its services to address this issue. The mayor also needs to develop relationships with surrounding communities. And while developing regional partnerships is essential and difficult, it does not require detailed climate knowledge prior to proceeding.

([i] From “When the Levee Breaks,” a 1929 song about the 1927 Mississippi River Flood. Written by Memphis Minnie and Kansas Joe McCoy. Recorded and popularized by Led Zeppelin, with many subsequent versions. One of my favorites is by Robert Plant & Allison Kraus. Lead image: Drone photo of Downtown Midland, Mich., flooded after two dams burst on the Tittabawassee River. Also seen is Dow Diamond and parts of Dow Chemical underwater. iStock photo taken on May 20, 2020.)