We set out by canoe from the Sylvan Avenue boat ramp just north of downtown and paddled our way 10 miles south to Loop 12.
"It is unusual for most major urban areas to have a virtual wilderness run right through the middle of it," he said.
Along the banks we saw abundant wildlife, especially birds such as Snowy Egrets, Great Blue Herons and Red Tailed Hawks. We also spotted beavers, turtles and Alligator Gar, a species of large fish that thrives in the river.
There are many signs of human activity along the Trinity, including ancient archaeological sites.
Allen pointed out a deposit of shells embedded in the riverbank, a telltale sign of a Native American campsite. The remnants of old pump houses and bridges also dot the meandering course of the river.
And yes, there is plenty of trash.
The entire stretch of the Trinity was littered with tires, trash and plastic -- even an old car.
At one point in the journey, our canoes scraped over an old pipeline that sits collapsed and rusting across the river's entire width.
But overall, there are pleasant surprises around every bend in Dallas' stretch of the Trinity River, especially considering its reputation.
"I think we're kind of in the process of rediscovering it," Allen said. "I think it touches something deep inside us."