Disturbed by the sound of the approaching boat, a heron stirs from its perch and takes flight, its broad wings flapping just inches above the water's glassy surface. Mullet jump in the bird's path. A warm September breeze sighs through the trees lining the banks of Buffalo Bayou. As the boat rounds a bend, this image of sylvan wilderness gives way to a glaring industrial landscape. Cranes belching smoke lurch around a scrap metal yard, and farther east the vats and pipes of a huge sewage treatment plant stretch along the northern shore. Achieving a better balance between nature and...