We'd like to share with you the process used for determining one specific setback in the zoning rules for the City of Portland.
This particular setback applies to properties that are in the "Scenic Resource" overlay zones.
According to the zoning code Title 33 chapter pertaining to this overlay zone, Section 33.480.040.B (480 Scenic Resource Zone (portland.gov):
Scenic corridor setback. A scenic corridor setback per Table 480-1 applies along street lot lines that abut the Scenic Corridor identified in the Scenic Resources Protection Plan. Development within an environmental overlay zone is exempt from this setback standard
So if it's determined that a property is within a "Scenic Resource" overlay (see this guide on how to find the maps to make such a determination: How do I find my zoning in Portland | UrbanForm), then the next step is finding the "Scenic Resources Protection Plan."
Some diligent Googling will turn up a PDF from 1991 that seems to be the document in question:
It's not easy to find this document in the convoluted government websites, for which many legacy links have been broken. Because of that, search engines seem to point to those old locations. As of January, 2023, it can be found here: Scenic Views, Sites & Corridors Resource Protection Plan - 1991 (portlandoregon.gov)
Also, because of the document's age, this PDF is just a scanned document. Therefore the text is not searchable. You have to read all 102 pages to find the "Scenic Corridor identified in" this document.
After some reading, it seems that page 63 seems to be the map that identifies this [these?] "Scenic Corridor."
As you can see, it's not a very high-definition map. It's hard to read. The next step to confirm would be to note the street names on the map and see if they match with any street names that pertain to the property we are studying.
Another option would be to search for some official GIS maps made available through public sources.
A search for "open GIS data Portland" turns up this dataset, which, by the title of it, seems to be a match for what we're looking for.
But opening up the dataset reveals that it is not a perfect match with the map shown in the 1991 document. It's slightly different. Some work is going to be required to figure out what geometry actually pertains to the "the Scenic Corridor identified in the Scenic Resources Protection Plan."
After some careful studying, we were able to isolate the geometry that seems to be a match with the 1991 document. The next step is to overlay that with geometry that is in the "Scenic Resource" overlay map since only properties for which this particular code section (33.480.040.B) applies will be affected.
We also have to note the next sentence in that code section: "Development within an environmental overlay zone is exempt from this setback standard."
So we have to also check to make sure the property is not concurrently in an "environmental overlay zone." Again, as a refresher, you can use this guide to find the official maps where overlay zones may be found: How do I find my zoning in Portland | UrbanForm
Once all of those conditional statements in the first paragraph are satisfied, we can then look at the table referenced by the code, Table 480-1.
Given that there is another exception in case the setback called out here in this table is smaller than the minimum setback specified in other overlay zones or plan districts, we need to check those setbacks and compare.
The IR and CI base zones don't have a setback that pertains specifically to streets (unless they are across from certain zones), so it's good to be aware of this modifying Scenic Resource setback.
The RM2 zone has base zone Front, Side, and Rear setbacks that are greater than this setback called out in Table 480-1, so it is questionable which will be considered to override (although a developer/designer/contractor could argue for the slightly smaller 480-1 setback, and have a strong argument given that it is specified that overlays, in general, override base zones, it is often a safer path through approvals to go with the larger setback, especially considering the convoluted path to determining the applicability of this setback).
The EG1 and IH base zones have street setbacks exactly equivalent to this 480-1 setback, so we then need only be concerned with setbacks in any other overlays or plan districts.
The same holds true for the EG2 and IG2 zones.
The real kicker is the 20 foot setback called out for "All other base zones." Subtracting the above zones (IR, CI, RM2, EG1, IH, EG2, IG2), we are left with these base zones:
Single Dwelling Zones (RF, R20, R10, R7, R5, R2.5)
Multi-Dwelling Zones- (RM1, RM2, RM3, RM4, RX, RMP)
Commercial / Mixed Use Zones - (CR, CM1, CM2, CM3, CE, and CX)
Employment and Industrial Zones - (EG1, EG2, EX, IG1, IG2, and IH)
Campus Institutional Zones - (IR, CI1, CI2)
Other (OS)
In these other zones, a base zone applied street lot line setback is much less than the 20' called out by Table 480-1.
So this Scenic Resource setback is important to heed for those sites "along street lot lines that abut the Scenic Corridor identified in the Scenic Resources Protection Plan", but not "within an environmental overlay zone", and without "larger minimum setback in overlay zone and plan district."
Interestingly, a call was placed and an appointment was made to confirm this analysis with the City of Portland. The official had never heard of this setback before, but after a long period of walking through these exact steps, came to be convinced that the analysis above was accurately applied.
It really makes you consider the Complexity of Zoning.
Thankfully, UrbanForm has incorporated this analysis so that any customer using UrbanForm will automatically be informed of the presence of this setback, its applicability, whether or not it applies to the property in question, and the specific sources and sections of the attributing code.
This is part of the work that UrbanForm has done to make sure that our customers are provided with efficient, accurate, and verifiable zoning information. This analysis and information, for dozens of processes similar to the above, is available instantly.
That's UrbanForm.