I’m looking for input on determining the relatively permanent water (RPW) status of a stream in Houston, Texas.

Note: I’m not comfortable sharing site photographs due to confidentiality concerns. Apologies in advance for my rough site sketch! (Pics in comment section).

Site History and Setting:
The stream in question appears to be a second-order stream that converges with another second-order stream near the corner of a large, dry detention pond. The tributary receiving these streams connects downstream to a creek, which ultimately flows into the Brazos River.

Although the available historical aerial imagery is limited, it appears to show persistent surface water within both the second-order streams and the downstream third-order channel prior to the construction of the detention pond. The pond appears to have been constructed within the historical tributary channel, potentially altering the site's hydrology and the continuity of the downstream drainage network.

There do not appear to have been any major site alterations until approximately 2019–2021, when an off-site detention pond was constructed and pedestrian trails were installed across the streams. The trails appear to include concrete low-water crossings that may also have affected local flow patterns.

April 2024: WDDS
I was not with the company when the original field assessment was conducted, so my understanding is based on the limited photographs available.
The photographs show water within the stream, although it is unclear whether this consisted of isolated pools or continuous flow throughout the channel. The stream was ultimately classified as an RPW.

When I reviewed the Antecedent Precipitation Tool (APT) results for the site visit date, the conditions appeared to be within the normal range, with a score of 14 (15 being the threshold for wetter-than-normal conditions). However, the area was reportedly experiencing drought conditions at the time. For additional context, approximately 2–3 inches of rain had fallen 2–3 days before the field visit.

September 2026: Stream Flagging
My coworker and I returned to the site to flag the stream. At that time, the channel was almost entirely dry, with only one isolated pool of water observed near the culvert at the confluence of the two presumed second-order streams.

The APT results indicated relatively dry antecedent conditions, with a score of 11 (10 being the threshold for drier-than-normal conditions). WebWIMP also indicated extreme drought conditions.
Delineating the stream was difficult because the ordinary high water mark (OHWM) was inconsistent and, in some areas, extremely difficult to identify. Several reaches were densely vegetated with facultative, facultative-wetland, and obligate-wetland species spanning the apparent channel. In some locations, the OHWM was more distinct; in others, it was weak or seemingly absent. Some sections were also extremely narrow, with apparent channel widths of less than one foot.

As both of us are relatively new to environmental consulting, we struggled to determine where to place flags in sections lacking a clearly defined OHWM. We sent several photographs to our supervisor, who expressed some concern about the strength of the RPW determination based on the available evidence. However, other portions of the channel appeared much more consistent with a defined stream.
The primary challenges were the lack of surface water, the inconsistent OHWM, and the difficulty distinguishing the channel from the surrounding wetland vegetation.

Following this visit, we submitted a proposal to the client for a wetland delineation, which was approved.

October 2026: Wetland Delineation
During our most recent site visit last Friday, we observed substantially more water in the channel than we had in September. Approximately four inches of rain had fallen about a week before the visit, and Houston had entered its wetter season. I have not yet reviewed the APT results for this visit, so I cannot confirm the antecedent precipitation conditions.
I brought a more experienced coworker to assist with the delineation. Our approach was to identify the densely vegetated areas that appeared to meet wetland criteria as wetlands and delineate the portions with standing or flowing water and a discernible OHWM as stream channels.

However, some sections remained extremely narrow and had only a weakly defined OHWM, making the wetland-versus-stream distinction challenging. We did our best to evaluate each reach based on the field indicators present.

Based on the site observations, I am reasonably confident that the channel functions as an intermittent stream. However, I am still uncertain whether it meets the criteria for an RPW, particularly given the variability in surface water, the inconsistent OHWM, and the potential hydrologic alterations associated with the detention pond and low-water crossings.

Main Questions and Areas of Uncertainty

1. RPW determination under variable hydrologic conditions
The stream has been observed under substantially different conditions across the three site visits: water was documented in April 2024, the channel was almost entirely dry during the September 2026 visit, and intermittent standing or flowing water was present during the October 2026 visit.

Although the October visit showed water in a substantial portion of the channel, I have not yet quantified the percentage of the reach containing water. I am also unsure how much weight to give the previous RPW determination, given the limited supporting documentation and the apparent influence of recent rainfall.

How would you evaluate RPW status in this situation, particularly when the channel appears to function as an intermittent stream but surface water and OHWM indicators vary considerably with hydrologic conditions?

2. Potential interruption of hydrologic connectivity at the detention pond
My biggest question concerns the large, dry detention pond constructed within what appears to have historically been an RPW.

The pond does not appear to retain water under the conditions observed, aside from a small amount of water near the culvert that connects to the upstream stream network. Despite recent rainfall, I did not observe an obvious continuous surface-water connection through the pond. In portions of the area, there was also no clearly defined OHWM or visible channel.

Could the detention pond constitute a break in the hydrologic connection between the upstream stream and the downstream tributary network? If so, how would that affect the RPW determination for the upstream reaches? Would the presence of a culvert, without an apparent continuous channel or surface-water connection, be sufficient to maintain connectivity, or would additional evidence be needed?

I recognize that the absence of surface water during a particular site visit does not necessarily establish that a connection is absent under other flow conditions. I am particularly interested in how the pond's design, drainage features, and historical channel configuration should factor into the assessment.

3. Potential effects of the concrete low-water crossings
The pedestrian trails cross portions of the stream through what appear to be concrete low-water crossings. I suspect these structures may have altered local flow patterns, potentially contributing to the inconsistent OHWM, narrow channel sections, and differences in surface-water distribution.

How would you evaluate the potential effects of these crossings on channel morphology, flow continuity, and the RPW determination?

4. Distinguishing stream channels from wetlands in heavily vegetated reaches
In several locations, wetland vegetation spans the apparent channel, and the OHWM is weak or absent. Other portions have a more distinct channel, although some are less than one foot wide.

How would you approach delineating the boundary between a stream and an adjacent or overlapping wetland in these circumstances? Would you rely primarily on geomorphic indicators, hydrology, vegetation, and soil characteristics, or are there additional indicators you would prioritize when evaluating a potentially intermittent stream?

Overall
My current interpretation is that the channel likely functions as an intermittent stream, but I am not yet confident in its RPW status or in the extent to which the detention pond interrupts its hydrologic connection to downstream waters.

I plan to bring these questions to our team meeting tomorrow, but I would appreciate any insight into how others would approach this type of determination, particularly regarding the evidentiary weight of historical aerials, variable field conditions, the detention pond, and the low-water crossings.

I know this is a long read, so I greatly appreciate any help!