![]() ![]() So there wasn’t much time for water to work its way downstream very far. I took these photos within an hour of the end of the rain. More rain fell upstream than at the gage shown above.Engineers didn’t count on the cumulative impact of insufficiently mitigated upstream development, some of which used beat-the-peak, hydrologic-timing surveys to avoid building detention basins.Planners used old (lower) Montgomery County rainfall data to determine the extent of the floodplain in their plats and plans.The developer hasn’t built any stormwater-detention-basin capacity to offset the increased runoff.Bulldozers compacted soil, limiting the rate of infiltration.We need an answer to that question before this development starts pouring concrete. How Can a 5-Year Rain Reach Almost as Far as a 100-Year Floodplain? The muck filled the wetlands for more than a mile downstream. But water coming from Royal Pines (right) is filled with sediment. Notice how water coming from the north (left) is clear. Contractors removed the silt fence last week. The developer removed it from the NW corner – where a neighbor has now flooded three times in two months. The SE corner of Royal Pines wasn’t the only part of the development missing silt fence. More Missing Silt Fence in NW Corner of Royal Pines From Harris County Flood Education Mapping Tool. The public also must foot the bill for increased water-purification costs. These shots also document the absence of silt fence on the eastern side of Royal Pines.Īll that silt will migrate down White Oak Creek and Caney Creek into the East Fork San Jacinto which the City of Houston just dredged at great public expense. Notice also how the floodwaters approach what appears to be some sort of water treatment facility in the upper right. Notice the water streaming through the cleared area and carrying away sediment downstream. The closer shot below shows water streaming through the soon-to-be subdivision and filling the Country Colony drainage ditch to overflowing. Think it’s just standing water? Think again. That big area filled with water, is a part of White Oak Creek cutting across Royal Pines. The water comes almost to the edge of the floodplain shown in the construction diagram above. Floodwaters from Creek Overflow Royal Pines If you were to project that line toward the lower right, it would roughly parallel the heavy black line that forms the eastern boundary of Country Colony, which you can see in the middle right of the photo below. I’ve circled the relevant portion in red. It’s the dotted line between Zone AE and Zone X. ![]() In the construction diagram below, the developer shows the edge of the 100-year flood plain. Now let’s look at how close that 5-year rain came to the 100-year flood line. NOAA Atlas 14 rainfall probabilities for Lake Houston Area. Harris County Flood Warning System hyetograph shows approximately 3.6 inches fell in two hours on 1/24/23.Ĭross-referencing that rate with NOAA’s Atlas-14 rainfall probability estimates for this area, we can see that 3.6 inches in 2 hours equals a 5-year rain. A check of nearby rain gages on the Harris County Flood Warning System, showed that the official gage at FM1485 and the San Jacinto East Fork recorded approximately 3.6 inches between 1 and 3 PM today. 5-Year RainĪ friend who lives a mile from Royal Pines recorded about 4″ on his rain gage for the full day. And missing silt fences let sediment escape into the wetlands that border the property. But floodwaters from White Oak creek approached the edge of the 100-year floodplain. According to Atlas-14 rainfall tables, that qualifies as a 5-year rainfall event. Between 1:00 and 3:00 PM on 1/24/23, approximately 3.6 inches of rain fell over Royal Pines in southeast Montgomery County. ![]()
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