What is a key method for protecting a sewer system from flooding?

Raising manholes above the 100-year flood level is essential for protecting a sewer system from flooding because it ensures that the access points to the sewer infrastructure remain above potential floodwaters. This practice minimizes the risk of water entering the sewer system during significant flooding events, which can cause backflow, overwhelmed systems, and contamination of local waterways. By elevating manholes, municipalities can reduce the likelihood of sewage overflow, maintain system integrity, and protect public health.

Other methods mentioned, while potentially useful in specific circumstances, do not provide the same level of comprehensive protection against floodwaters infiltrating sewer systems. Lowering manhole covers, for instance, might seem counterintuitive since it would actually increase the risk of floodwater entering the system. Similarly, standard seals are critical for maintaining system functionality but may not be sufficient to address flooding risks on their own. Constructing systems without pumps could lead to greater challenges in managing wastewater flow during flooding scenarios.