From 1933 to 2011 – One Increment at a Time
Topographic mapping from the U.S. Geological Survey and identification of wetland soils from early aerial photos of Denver show that by 1933, buildings had already been constructed on some of the bottomlands between 13th Avenue and Colfax Avenue from Leyden Street to Ivy Street. Where are those sites, mentioned in last month’s column, with reference to 2014 landmarks?
Between 13th and 14th:
“Facility south of 14th between Leyden and Krameria” – now a Safeway store and parking lot;
“Buildings south of 14th on the east side of Kearney” – now a King Soopers parking lot, commercial building at south end of parking lot, liquor store at north end, and Safeway gas station. The King Soopers store itself is west of Kearney, on land that was vacant and included wetlands in 1933.
Between 14th and Colfax:
“Between Leyden and Krameria, wetlands extend pretty far north of 14th” – now a newly refurbished strip mall;
“City Floral, or its immediate predecessor, … along Kearney” – now City Floral, electric substation, shops on west side of Krameria just north of 14th;
“A lot of regrading activity south of Colfax, probably including a good deal of filling” – now include various businesses along Colfax from Kearney to Jersey;
During a rainstorm larger than a 5-year frequency storm, the future underground pipes called for in Denver’s Storm Drainage Master Plan could not prevent some level of overland flow from 13th and Leyden to Colfax and Ivy. During a 100-year storm, flows from Leyden to Ivy could be expected to range somewhere between 340 cfs upstream of the intersection of Leyden and 13th and 1360 cfs downstream of the intersection of Ivy and Colfax.
Granted, those 5-year pipes are not in place yet; nevertheless, I observed the phenomenon of overland flows during and after a major thunderstorm on July 7, 2011, and then again in 2012 and 2013.
Being a floodplain manager can mean you may sometimes behave like stormchasers chasing tornadoes. I eagerly walked all over the area affected, well beyond 13th Avenue to the south, Colfax to the north, and beyond Leyden to the east and Ivy to the west. I brought some topographic maps (2-foot contours) I printed from Denver’s GIS database on my walks and sketched the lines of debris deposited during the flood, documenting the outer limits of flooding.
In 2012 and 2013 I did a little checking of my 2011 maps to better understand some of the details of the flooding patterns.
The map above has been clipped from my 2011 flood documentation map. Not surprisingly, the soils patterns and patterns of regrading and the placement of fill from the 1933 aerial photography seem to be the skeleton for the 2011 patterns. I won’t go through the details. I will, however, note that gas stations and electrical substations are not particularly appropriate uses for floodprone bottomlands. Single family houses and apartments with basements, even on fill, can result in simultaneously experiencing basement flooding and the forcing of floodwaters from that location to another location. Garden centers or auto repair facilities may be slightly more appropriate, preferably with some kind of flood protection.
Constructing streets subject to 18 inches or more of moving water is an invitation to strand motorists in their floating cars. From 1933 to 2011 all of those scenarios played out, one increment at a time.
Since 1933, as each individual increment of land use change was proposed, approved, and implemented, the creek has had one less choice about where to flow.
Brian Hyde is an expert in floodplain management and stream restoration. He wants your feedback at westerly_connect_brian@comcast.net or 720-939-6039.