I took a geography course in college (strictly for a necessary general elective--never thought I'd use what I learned.) One of the topics covered was the dynamics of rivers and what causes floods in certain places. Simply put, as water flows, it takes the path of least resistance, eroding the softer parts of a riverbank. Eventually this is what causes bends in an old river like the Schuylkill. The outer part of each bend is called the cut bank, where the land's being slowly washed away. The inner part is the slip off bank, where the river deposits the sediment from the cut banks upstream.
If there's a big storm, or a weeks' worth of heavy rain, the process speeds up--more land erodes from the cut banks. It can undermine bridges and buildings, or if he cut bank is low, the whole area floods. You could build a flood wall, of course, but the water has to go somewhere, so the slip off bank on the other side of the river will take the brunt and wash away. Sort of like pool balls--bounce them off one side of the table, they'll hit the other side.
On the photo of the Norristown/Bridgeport riverfront above, I've marked the cut and slip off banks. On the upper bank, you can see 2 vacant lots, one to the southeast of the "A" and one right above the lower slip off bank. Both are under consideration for immediate development.
Building on the lower lot might not cause serious problems. That's where the river deposits sediment anyway. The upriver lot is on a cut bank though, so if the development is too close to the river, or uses too many hard surfaces, or a flood wall, the water will cut into the slip off bank on the Bridgeport side. Now, that's where there was a big fire several years back, so at present, there's nothing much on that bank to be damaged by a flood. But, if we have a REALLY big flood, the cut and slip off banks can actually reverse themselves, which would flood that next new development downstream.
The more surfaces that can't erode along the river, the faster the water flows. In a flood, the force created can be as destructive as a power-washer. The next large bend downstream in the river contains a water treatment plant, the supports for the Turnpike bridge, and high-tension electrical wires. If a violent flood hits there, a lot of vital infrastructure is history.
So sure, develop along the river in Norristown, but keep the structures and paving back far enough that they won't cause future catastrophies. Leave some open space, with natural grasslands, or a wide forested area--something to act as a buffer when the river rises. A non-paved nature trail off of the existing bike trail would be a great use of this buffer zone, allowing residents to enjoy the riverfront, and wouldn't cost a fortune to reconstruct after each flood.