11/18/23 – It was a busy week for the new Northpark South development. A Drainage Impact Analysis submitted to Montgomery County for the development at the west end of Northpark Drive shows that the developer intends to drain its property through adjacent sand mines owned by other entities. The analysis does not address potential sedimentation issues.
The developer also applied for several variances from the Houston Planning Commission.
Meanwhile Century Land Holdings of Texas, LLC continued clearing land at the west end of Northpark Drive that borders the sand pits along the West Fork San Jacinto River. In the last week, contractors have cleared approximately one third to one half of the 54.4 acre development.
Drainage Analysis Shows Routing
A drainage impact analysis obtained from the Montgomery County Engineer’s office reveals that:
- Drainage from 107.2 acres outside (upstream from) the development flows through the development on its way to the West Fork.
- The remaining 43.2 acres will contain 236 homes on narrow lots for an average of 0.18 acres/home (1/6th acre) with impervious cover of 66%.
Drainage from the development and areas upstream will be routed into an on-site 11.2 detention basin (above) and, from there, into sand pits and the West Fork (below).
The drainage analysis claims the outfall from the proposed detention basin will not increase flow to the sand pits.
The analysis by RG Miller also indicates that the on-site basin will provide a storage rate of approximately 1.26 acre-feet per acre. That exceeds the minimum of .55 acre-feet per acre recommended by Harris County Flood Control District for sites this size draining into Harris County.
RG Miller claims that the water surface elevations in the sand pits will decrease during both 25-year and 100-year storm events.
The engineering firm also claims that the proposed development lies outside the 100-year floodplain of the West Fork. However, that claim is based on old data.
New flood maps, expected to be released next year, will likely show the floodway and floodplains expanding by 50- to 100%, according to preliminary guidance from HCFCD and FEMA.
However, RG Miller makes no mention of the shifting floodplains. Nor do its engineers mention any wetlands on the property which the US government clearly shows.
The engineering firm concludes that their design will have “no adverse impact” on downstream properties. Nor will it “unreasonably”:
- “Impede the natural flow of surface waters from higher adjacent properties”
- “Alter the natural flow of surface waters so as to discharge them upon adjacent properties at a more rapid rate or in a different location…”
One hydrologist I interviewed about this plan said, “Well, this isn’t how I would do it. He is draining directly to the sand pit and showing that he isn’t increasing flows going to the sand pit. Nowhere in the report did he document that he had permission from the sand pit owner to drain to the sand pit. Also, he didn’t have any field survey to back up how he knew the topography and details on the hydraulic connections between the sand pits and the river. So I don’t know how he can be certain of his results.”
The drainage analysis did not address what effect the proposed routing would have on sedimentation. The outfall to the drainage ditch is already severely restricted by sediment accumulations.
A request for variances obtained from the Houston Planning Commission shows a different outline for the property. It omits the areas designated as commercial at the entry.
The MoCo Appraisal District (MCAD) shows that Hanover Estates owns the parcels that bracket the entry. MCAD also shows that Hanover and another company called Maryfield LTD jointly own the sandpits. The drainage analysis does not address the ownership issues or permissions.
Requests for Variances from Houston Planning Commission
This property lies within the City of Houston’s extra territorial jurisdiction. The developer requested three variances from the Houston Planning Commission:
- To allow lots less than 5000 square feet.
- To exceed intersection spacing by not providing a southern stub street (outlet).
- To exceed intersection spacing by not providing an east/west street
The planning commission has not yet responded to an information request about whether it granted the variances. Meanwhile, clearing continues.
One Third to One Half of Site Now Cleared
In the last week, contractors have taken down an estimated one half to one third of the trees on the site. See below.
Compare that to this previous post.
At this rate, the entire site could be cleared by early December.
A Closing Thought
The goal of most drainage studies is to figure out how to develop property safely. If all of the studies were always correct, we would never flood. But we do. Why?
And why is property that was too dangerous to develop before Harvey now safe after Harvey … when we now realize how much greater the risk is?
More on that in my next post.
Posted by Bob Rehak on 11/18/23
2272 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.