What causes lakeshore flooding? - WNEM TV 5

First Warn 5

What causes lakeshore flooding?

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Heavy flooding at a Bay County mobile home park. Saginaw Bay visible in the background. Heavy flooding at a Bay County mobile home park. Saginaw Bay visible in the background.
Strong winds push water onshore. Strong winds push water onshore.
The stronger the winds the greater the flooding. The stronger the winds the greater the flooding.
Brown water and debris still shown in the Saginaw Bay Saturday afternoon. Brown water and debris still shown in the Saginaw Bay Saturday afternoon.
(Source: WNEM) (Source: WNEM)

The wild weather we had this past Thursday caused a number of problems around the region. From power outages, to ice/snow, and lots of flooding, it was certainly a very active day. With all these warnings issued this past week, there was one you may not have heard before, especially if you are new to the region. A Lakeshore Flood Warning. For those that haven't heard of these warnings, or what causes lakeshore flooding, I wanted to take a brief moment to talk a little bit about these somewhat rare warnings. 

What does this warning mean?

This type of warning means that flooding along the lakeshore is or will soon be occurring. This means homes and roads near the coast may be flooded temporarily. Beach erosion is also a concern with these weather conditions. 

Why does it happen?

These conditions usually happen in high wind environments, but you need a few more conditions to be right as well. First, the further the wind can travel across the lake the more intense the flooding will be. As strong winds cross the lake, in the case of this past week winds that were around 40 to 50 mph, they kick up waves and push the water. These waves crash along the shore and push water inland on their own, but with a sustained wind across the lake, water will actually be pushed to one side of the lake, raising water levels on one shoreline, while usually lowering them somewhere else. 

This past week we had strong northeast winds traveling all the way along Lake Huron and straight into and along the Saginaw Bay. This pushed water pretty deep inland, including the large waves, which caused areas near the shore to become flooded. This effect is very similar to storm surge and coastal flooding during a hurricane. The stronger the winds, and the longer their path across the water, the more severe the flooding event will become. 

What happens next?

The good news, with the exception of any low lying areas that become filled with water, is that the flooding event should come to an end as soon as the winds die down and the lake waters settle. The damage these flood waters cause can usually be seen in the lake water the next few days. It is not uncommon for the water to take on a brown or dirty color from the dirt and debris it picked up. Additionally, floating debris will be visible either in the water, or stuck to the shoreline after the event. Depending on the severity, clean up may take some time. 

More good news is that these events are not overly common. In fact the event on Thursday was the first Lakeshore Flood Warning the NWS Office in Detroit had issued since December of 2015, some 463 days ago according to records from the Iowa State University of Science and Technology. This included Bay and Tuscola counties, though the actual number of days since their last warning may be longer, as county level records are not maintained.

While each event is different and will result in a different level of flooding, they should all be taken seriously. In this, just like any weather event in Mid-Michigan, the First Warn 5 Team will have you covered, providing you with the information on warnings and flooding that you need to stay safe, on-air, online, and in our mobile app. 

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