Nobody's measured it, but I'm sure tens of thousands of miles of small urban channels have the unresolved problems I study.
I've just finished a couple of days in the field with Nick Nelson of Inter-fluve. We're doing a geomorphic study of a small municipality in northern St. Louis County. The EPA-funded project will help them preserve and restore environmental values in a small creek, resolve infrastructure problems, and, most importantly, have a sustainable plan.
Most of this community was built in the 1940's and 50's and has problems typical for the time--stormwater and even sanitary sewers were added late, weren't built properly, and the creeks are a Frankensteinian mix of public and private stabilization projects. In the top photo you can see some of this, and yep, that is a utility pole set in the middle of the creek.
We recorded reaches where more than 98% of the bed materials were anthropogenic: concrete rubble, glass, asphalt, displaced riprap stones, even well rounded chert gravel mined from big rivers miles away and dumped on banks. Beyond understanding the urban geomophology, we have to consider how it might all be fixed, things like access for construction; many of the houses are too close together to admit heavy equipment. In St. Louis houses have been condemned and torn down so sections of creek could be stabilized.
Last night Nick and I met with the City Council and about 25 residents, and in spite of the inevitable conflict and emotion over who's responsible when houses are falling into the creek, I enjoyed it very much, partly because it's a good use of my expertise, but mostly because both the citizens and aldermen impressed me greatly with their courage, character, and civility.
It was cold, and we broke ice most of the time, surveying nearly a mile of creek. We went underground, and there encountered a sewage spill--this municipality has a combined stormwater/sanitary system. These are being phased out for good reason.
Here you can see Nick at the end of a long culvert, and also as we survey a section of stream with complex responses to multiple impacts; an undersized culvert outlet, displaced undersized rip rap. You can't see the two houses 10 meters (to the left) above him, tenuously held by a rotting wooden retaining wall. You can see the invasive shrubs and vines doing their best to kill the trees. Another variable.