What looks like a simple riverbank is actually a time capsule of the Saugus River’s past.

This photo was taken along the Saugus River, just upstream of Rumney Marsh but still within the tidal zone. Here, the river’s flow is shaped by the same tides that influence the marsh, creating a transition between fresh and salt water habitats.

The darker bands are compacted peat, formed from centuries of decayed salt marsh grasses. The lighter layers are mineral-rich silts and clays deposited by tides and river floods. Together, these layers show how the marsh has gradually built upward over hundreds or even thousands of years as sea level has slowly risen.

If you look closely at the top of the bank, you can even see two distinct zones of vegetation. The bright green band closer to the waterline is likely smooth cordgrass, which thrives in the low marsh and floods daily with the tide. Above it, the straw-colored layer is most likely saltmeadow cordgrass and other high marsh plants that flood only during the highest tides. Those two layers mark the difference between high and low marsh, showing exactly how subtle changes in elevation shape what grows where.

These edges erode when waves, boat wakes, or strong tides undercut the base, causing sections of the marsh to slump into the river. The result is a stepped, terraced look that exposes the marsh’s interior. What seems like simple erosion is actually a window into the marsh’s history, showing how it grows, collapses, and rebuilds over time.

Further inland, where tidal energy is lower, edges tend to soften and re-vegetate as sediment and new plant roots stabilize the surface. Along this portion of the Saugus River, the stronger currents and greater tidal range create sharper, more defined cuts like the one in this photo.

This small section of riverbank helps tell the story of how our tidal wetlands form, erode, and adapt over time.