FAQs

A 100-year rainfall event describes a storm of such extreme intensity that it has only a 1% chance of being equaled or exceeded in any given year. It's a statistical probability, not a calendar forecast. For example, in a 1-hour period in Northeast Ohio, a 100-year storm would drop approximately 2.0 to 2.4 inches of rain, overwhelming most local sewer systems. For comparison, a 50-year event has a 2% chance of occurring in any year and would drop approximately 1.8 to 2.1 inches of rain in that same hour.

The catastrophic flooding that struck Hudson, Ohio on August 8, 2024 was far more extreme than a 100-year event. The total storm rainfall was estimated at 6.98 inches in a 24-hour period.  The National Weather Service reported that the rapid downpour of 5.24 inches of rain in just 2 hours was an event corresponding to a return period of approximately 2,000 years (a 0.05% annual chance).

The most significant factor is that the air itself is getting warmer, allowing it to hold much more water vapor. When a storm moves into the area, there's simply more moisture available to fall as rain. This means that when it rains, it pours! Precipitation is arriving in shorter, heavier bursts, instead of being spread out over longer periods. Data shows this trend: for the entire Midwest region, including Ohio, the amount of rain falling during the most extreme 1% of storms has increased by 42% over the last several decades (Source: U.S. Environmental Protection Agency, analysis up to 2016).

Flooding is happening repeatedly in the Hudson and Northeast Ohio region due to a combination of changing, extreme rainfall patterns and limited capacity in existing local infrastructure. The general trend for Northeast Ohio, and other parts of the Country is wetter, with precipitation falling in shorter, heavier bursts that overwhelm drainage systems. For example, the total rainfall for January through June 2025 was approximately 11.6 inches above the long-term average for our region. After months of above-average rain, particularly from February through June, the ground becomes completely saturated. When the ground is full, it cannot absorb any new moisture, meaning every drop of rain immediately becomes surface runoff. This massive, rapid volume of water rushes into the storm sewer systems, which cannot be constructed to handle extreme events like the 2,000-year storm on August 8, 2024 without massive stormwater storage facilities.

A Watershed Study is a detailed engineering analysis of how rainfall flows across the entire land area that drains into a local waterway. The Study helps your neighborhood by pinpointing the sources of flooding and drainage failure, allowing the City to develop targeted solutions like upgrading pipes or building new water retention areas to lessen the impact of the storm.

The Storm Water Management Study is being developed to identify solutions to protect the City’s most vital infrastructure, including homes, critical buildings, and roads, from severe flooding. However, this is a major challenge because it's virtually impossible to eliminate all flooding during extremely rare, catastrophic rain events like the storm on August 8, 2024.

Instead of attempting to eliminate all flooding, the City will utilize Level of Service (LOS) Goals to set practical targets for future flood mitigation projects and build resiliency in the overall system. For example, the study will focus on reducing roadway flooding during smaller, more frequent rain events (like a 25-year storm) while prioritizing the protection of homes and businesses from structural flooding (water entering the building) during very large, less frequent storm events (like a 100-year storm).

Basements can flood from heavy rain for three primary reasons, even if you're not near a creek. 

1. Severe storm events can cause the public storm sewer system to become surcharged— meaning the pipe capacity is exceeded, forcing pressurized water to back up through your private service line into your basement. 
2. Intense or prolonged rain can cause the groundwater level to rise, overwhelming your sump pump and foundation drains, which then exerts hydrostatic pressure against your foundation and forces water through cracks or joints. 
3. Poor surface drainage, such as ground that slopes toward your house or downspouts that discharge right against the foundation or may be connected to the footer drains, can direct large amounts of water to pool against your basement walls, allowing it to seep through the foundation of your home.

No, the on-going storm water hydrologic and hydraulic (H&H) study will not directly evaluate sanitary sewer backups into homes, as it is focused solely on the movement and quantity of surface runoff. While the study identifies the high-volume runoff that can impact sanitary sewer  systems, a separate sanitary sewer system study would be needed to assess the sanitary sewer system's capacity and vulnerability to groundwater infiltration and inflow (I/I).