High Water In Hillsboro Closes Roads And Parks

Water, water, everywhere! The month is not over yet, but Hillsboro, Oregon, and the valley will end up at the end of this month with a January 2024 total of 8.5+ inches. We average 5.14 inches in January historically. All the water is running literally all over the place, and it has flooded several roads and many creek crossings here in Hillsboro. The soils are saturated. The snow and ice are an added frustration.

Our readers have been reaching out and posting photos on social media. The City of Hillsboro has also posted warnings about a few closed roads.

Hillsboro local photographer Rick Dalrymple reported and showed his photos of the East bridge at Noble Woods Park. The water is so high that the bridge is almost entirely underwater. This is not completely surprising because the bridge is in the flood plain like most crossing our streams. Let’s hope it survives unscathed.

Noble Woods Park as seen in late January 2024 – photo courtesy of Rick Dalrymple

Of more concern is the flooding occurring along Glencoe Road and Harewood Drive in NW Hillsboro. This situation is causing a lot of traffic to divert through neighborhoods, turn around, and travel out of direction. Have a look at the posts by the City of Hillsboro. Other photos have shown cars caught in the water with people trying to walk away.

Because this is abnormal, we thought we would look upstream for answers. The culvert that goes under Glencoe Road is undersized so that certainly has to be considered, too. Here is a look at the drainage that runs through this important part of Hillsboro.

The red arrows identify the downstream areas of two drainage creeks that carry the drainage from neighborhoods to the East, the INTEL Jones Farm, the Hillsboro Airport, and a lot of the new expansion areas in North Hillsboro where the Industrial projects have popped up in just the past 18 months. While those projects are supposed to have inside drainage ponds to hold water before it is discharged, this amount of rain and ice could have sent more water down the stream corridors than the old culverts could handle. The downstream cost of this sort of growth can often best be seen when things get like this.

As seen from Google Earth, here is a shot of the data centers, factories, Amazon, Genentech, and airport expansions that have happened in the last 1-3 years.

The storm basin that feeds the creeks and drainages actually starts on the Genentech property on Evergreen Road and the Stack Data Center property. The red arrows depict new developments with acres of hard surfaces, also called impermeable surfaces, into which water can not flow. So, it is plausible and all but provable that these new users have significantly increased the downstream flows. Tens of thousands of gallons of additional water each hour headed West, and when it reaches Glencoe Road, there is just too much of it.

A little research also verifies in this case that the Glencoe Swale culvert under the road is a 48″ wooden box culvert. Hillsboro Public Works has had the replacement of that culvert as a high priority for years, but it appears funding for this project has not happened. It needs to be done, and money from the upstream developments, which cost tens and tens of millions of dollars, should help with this work.

Here is what I found online:

With dozens of new industrial buildings and users coming to the North Hillsboro areas, which will need to discharge stormwater into this basin, now is the time to replace that Culvert.

We will check with Public Works to see if this Culvert has funding or is moving up the list of priorities. It must be done; sometimes, reality and public safety must be prioritized over studies and plans. I am confident that Public Works and the City Engineering team are working on this, and we must fix it. With the climate warming and getting wetter, we must be ready for these once-and-while happenings to become regular occurrences.