Some info on flood/ditch mediation ...response of City and WRAB

Jeffrey P. sent me some interesting information on the flood/creek/ditch research he signed up to do at the last meeting.  Susan went to the  Water Resources Advisory Board (WRAB) meeting on Monday night and spoke to the WRAB about our concerns in the GGNA area.

What follows are his notes.

In the Boulder city’s site—take a look at the final Boulder Creek Report.  There is a project plan on p. 7 (pdf page, page 3 normally) that shows the creek that was included in the floodplain mapping.  There is an arm of the creek called Boulder Slough (the ditch follows it) that hasn’t been included in the mapping!  Apparently it’s an original part of the creek, the ditch just followed it, and it will be mapped in the next few years.  I think that means we are a lot closer to a floodplain than we thought and that the ditch will become a flood way that needs to be managed.  That could be good news if they do flood mitigation on it—and maybe bad news depending on the floodplain mapping.

Based on this information from the city’s flood maps, there is no question that the city has responsibility for floodplain management in that ditch area—the question is—what will it do and how will the ditch people get in the way? 

Based on what the WRAB had to say, it will be an uphill fight to get the city or the Ditch owners to either widen the ditch itself or change the bridges to allow pass through of flood water.  Rule number one is that whatever flood remediation the city undertakes cannot simply pass flood water further down stream to cause flooding in another jurisdiction.  More importantly, the widen, deepening or changing of the bridges are 18, 19 streets, etc would be hideously expensive; the city would have to compensate residential and commercial owners for  any setbacks, etc. (Interesting note: Our GGNA ditch is named the Boulder Slough and was originally a tributary of Boulder Creek; around 1860 it was incorporated as an "irrigation" ditch. So it is both an irrigation ditch and a tributary of the creek.)

However since the city is planning to build new city structures from 9th to 13th or 15th Streets, they will have to address the Ditch that passes through the GGNA area. That may give us some leverage to get the city planners to look at the clogging/debris build up in the GGNA area.  

It was clear that the city intends to implement the plans/studies already in places severely damaged by the flood such as  South Boulder Creek, Gregory Canyon Creek, Two Mile Canyon, BlueBell Canyon. These areas will probably all receive repairs/work before the GGNA area..

( See www.boulderfloodplan.net for more information. Also look for the Flood control page in the WRAB portion of the city's website; you want the Ditch and Reservoir Directory which will provide usual info on the data the city is using to assess damage, remediation, etc.)

The residents in the GGNA area need to put their flood damage information into the "Crowd sourcing site for the flood, " so this information is available to the Utilities Dept which is handling repairs and remediation, planning for  the city.  Link to follow.

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