CodeNEXT: Replace Impervious Cover Limits with a Tax?

A uniform (but HIGH) tax per square foot of impervious cover is a good idea even if it applies only to the city of Austin and its ETJ (but more likely we would want to apply this to all water utility customers instead, which is somewhat different population).

In the urban core, where land is very valuable, people would be willing to pay even a high impervious cover tax because they have more useful uses for the land than as stormwater sinks.

In the fringes, where land is NOT very valuable, we would expect to see much more ‘sink’. This is a good outcome, a natural outcome, and what we should seek as a “nudge the market” solution that improves the environment while also supporting urbanism.

I don’t care what Round Rock and Pflugerville do in this scenario. It’s still good for Austin to do it.

But given that we have a lot of unmet needs in current infrastructure, I would argue that the tax must be HIGH. Not trivial. The effort should be to construct a tax that in its first year roughly equates to an increase over any fees that support drainage infrastructure for even a low-impervious-cover house. I’m fine if this results in a tenfold increase in “fees paid to support drainage” for a property in the core that exists today, as long as it provides correct incentives for future development.


Increasing the drainage fee 10X, as a start, is fine with me. We need to have a change of mindset and not look to property taxes as the only game in town, that hand has been way over played for too long.

That’s exactly right. If you made it high enough to be effective downtown it would utterly stifle development.

Kind of the whole point in some sense – a square meter of impervious cover has about the same negative effects almost wherever it is (at least compared to the extreme differences in the effective costs of lot-based percentage limits).

We’d use less impervious cover overall (and be better off) if we concentrated that impervious cover in places where each additional acre of IC gets us more built square feet, more dwelling units, more retail office/space, etc – and stifled development in places where we don’t get much out of extra impervious cover.

So I don’t want it to be quite high enough to reduce IC in or near downtown; in fact, I want it to reduce the effective cost of IC in the central core. I do want it high enough to utterly stifle new suburb growth.

The problem with that is, the runoff won’t stay in downtown.

Neither will runoff in the 'burbs stay out there. That’s the point – extra IC near downtown means much less IC on the periphery and less runoff over the whole watershed.

Maybe, but runoff in the burbs might only flow onto vacant land. Runoff from downtown might flood people’s homes and businesses.

We plan on putting these recommendations to a vote starting sometime tomorrow. If you have any further specific recommendations for wording changes or examples that can be used in the “rationale” section such as links to specific research or articles, please let post here sometime today! I’ve included what I believe to be the latest wording for this recommendation below based on what everyone has said here, but if I missed something, please let us know.

@Phil_Wiley I think the following would include increasing the drainage fee since the resolution just says “tax” and the city or someone could figure out later what that tax looks like or how high it should be?

@Shawn_Shillington are you suggesting to add language about “fee in lieu density bonus to increase impervious cover \ building coverage” somewhere in the resolution?


Replace impervious cover limits with a tax, applied uniformly throughout the city, on impervious cover (or, if feasible, on likely run-off). Detention ponds, green roofs, and other measures could lower the tax liability based on likely runoff reduction.


  • Limits on impervious cover are arbitrary and a “blunt instrument” that ultimately constrains housing supply and diversity.
  • A uniform tax on impervious cover or likely run-off is a more effective way of reducing the amount of run-off and the cumulative effects on flooding and water quality.

Just a different way to phrase it - I think the language you have now is fine

The relevant issue here is “what tax”.

Environmental preservation specifically of Barton Springs has been misunderstood since it’s inception when in 1980’s the science was not well understood. Subsequent ACADEMIC studies state that limiting impervious cover has the practical impact of increasing sprawl. This may to be counter intuitive.

Studies show that impervious cover in UNREGULATED development of the Barton Springs Zone is about 22.5%. That is actually LESS THAN the 25% limit in the contributing zone of the SOS ordinance. Other studies show that impervious cover of 20% can still mitigate flooding impacts. This is the finding of studies by the City and other academic studies. Water scientist Dr’ Michael Barrett shared studies with me that were reaffirmed by civil engineers working in Austin that the real threat to Barton Springs is PET WASTE.

A study in 2008 to 2011 during periods of drought and floods showed that the source of pollution during rain events was surface runoff. The filamentous algae that boys throw at girls in Barton Springs comes from nutrients coming from PET WASTE - surface runoff - in suburban neighborhoods. The study showed that the greatest threat was from Travis County near Loop 1 and SW Parkway. (a bunch of elderly folks maybe?) Who knows?

Measuring environmental impact of development using impervious cover PER ACRE actually defeats the goal of limiting the impact of development on environmentally sensitive land. The Urban Land Institute suggests the better metric - the more useful way to measure environmental impact - is impervious cover PER CAPITA. The latter metric implies that greater density - more people per acre - reduces overall impact of population growth on environmentally sensitive land.

If we project population growth of 250,000 people in 50 years (as is the case in the Barton Springs Zone), is it better put build 100,000 homes over 100,000 acres (sprawl) or 10,000 acres (urban norms) or less like 7 homes per acre that support mass transit?

Which form of development is more likely to provide tax revenue to protect environmental water quality protection land? Sprawl - that does not support public safety services, road infrastructure or schools? Density that has significantly less impact PER CAPITA and provides ten times the tax revenue compared to sprawl?

The policies Austin has adopted to protect it’s environmental resources since the 1980’s has been misinformed and misguided. And I too have made misguided assumptions about sprawl. The latest studies show that the environmental impact of septic systems is not significant, as I had assumed. During periods of drought, the background contribution of Nitrogen, Phosphorus and Potassium were not significant. That would have been from septic systems. It was surface runoff that was the significant contributor to the pollution that affects us at Barton Springs and that came from pet waste.

That does not let farming activities off the hook. Recent studies by scientists working with Walmart and others on environmental impacts of commercial activities show that fertilizer as modified by bacterial activity create nitrous oxide that significantly contribute to green house gasses and global warming. Reducing the carbon footprint could NOT be limited to green roofs and natural gas powered trucks. Efforts had to go back further into the supply chain - the farms and the chemical companies that guide how they grow crops.

Opinions and feelings really do not have a role in this discussion. Yet here we are. People suggesting what policies we ought to pursue. I suggest that those who want to contribute to this conversation ground their comments in science.

The proof is that in 1985 there was no algae in Barton Springs. As late as 2006 a comment in the Austin Chronicle notes that Barton Springs was ruined for that person. My grand daughters saw a video of Dee McCandless’ Aquafest water dance I participated in in 1985. No algae. Barton Springs has been ruined in my lifetime and I am sorry to witness it’s demise.

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As it’s more to promote a new approach and change in direction than a detailed/specific policy, I am fine with the wording and leaving wiggle room for improvement @Pete_Gilcrease.

Believe it would be consistent with the proposal and comments to make a very minor edit if you choose to.

Replace impervious cover limits with a tax/fee, applied uniformly throughout the city, on impervious cover, or better yet, on likely run-off. Detention ponds, green roofs, and other measures could lower the tax liability based on likely runoff reduction.

@kimberly, most of Downtown is already zoned at or approaching 100% impervious cover. The proposal would make it more attractive to build near Downtown’s borders, which could affect the watersheds. The model should be to make the fee high enough that there is a clear incentive to retain on site where feasible, for either existing or new construction.

@ted knows a lot more about this stuff than most, I believe that cover near the lake has much less impact on the watershed than cover further upstream. Heavy rains near the lake make it into the lake pretty quickly, it’s the stuff upstream that comes in later like a tidal wave that causes damage.


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Thanks for sharing your expertise and urging a scientific approach to addressing water quality and protection of environmentally-sensitive land.

I see at least three ways to measure impervious cover for the purposes of taxing or imposing fees on it:

  1. Square footage of impervious cover per acre (or percentage of impervious cover on a lot).
  2. Square footage of impervious cover (the amount of impervious cover on a lot, regardless of the total lot square footage).
  3. Square footage of impervious cover per person.

The initial proposal in this discussion thread was for (2), simply the amount of impervious cover, no matter what the lot size. Several participants noted that this measure, taxed at a high enough rate, would discourage sprawl development, perhaps to a severe degree. Perhaps going even further with (3) is not necessary to encourage desirable development patterns?

Several people have brought up flooding as an issue, which has ramifications beyond water quality but also on safety and risk of property damage. Do you have any thoughts to share on that issue?

Finally, should the revenue from any tax or fee on run-off be dedicated to water quality and detention infrastructure of the type suggested in one of the other proposed resolutions on CodeNEXT?

Has the FAN board voted on all these recommendations? If so what where the vote counts for each.

I can start a separate thread if needed.

The FAN board does not vote as a body on policy resolutions to “filter” them before bringing them to a vote of the full membership. FAN is not a top-down organization.

The procedure is for members (including directors on the board) to initiate a discussion here in this forum on a potential resolution, to invite participation in the discussion, and for at least one board member to “sponsor” the resolution once she deems it suitable for a vote of the membership. (Sponsoring a resolution does not necessarily imply endorsement.) Once sponsored and packaged onto a ballot, a resolution goes before the full membership for a vote.

It is true that members of the board vote on resolutions just as all members of FAN have the opportunity to do. If you’re curious about how each member of the board has voted, or plans to vote, on these resolutions, then you are certainly welcome to start a new thread and ask.

I really like all of the resolutions and think, if implemented, would give us a great land development code. There are probably more issues FAN could have voted on too, but I think these are some of the main big issues. I voted through Helios already and I supported each resolution (not as a board member, but as an individual member of FAN).

In the past I have heard that the challenge with existing NON-compliant commercial development was or is that the SOS redevelopment ordinance requires financially impractical constraints upon property owners. Specifically, the loss of revenue while redeveloping, demolition costs, detention pond construction and engineering costs together or even individually are too great a burden for property owners to redevelop.

To be fair, not all property owners are the same. Of the 199 properties (666.5 acres) targeted when crafting the redevelopment ordinance (to bring non-compliant properties into compliant and reduce pollution) 140 parcels are less than 3 acres. and the smallest might be 1/2 acre for a gas station. At the other end of the spectrum is Barton Creek Mall at 112 acres and 90+% impervious cover. The largest 20 parcels (10%) are greater than 15 acres and in the middle 40 parcels are between 3and 15 acres.

All 199 parcels are currently a source of pollution from parking lot runoff and lack SOS compliant flood control ponds. SOS and the redevelopment ordinance as implemented by the City are an impediment to cleaning up pollution in the Barton Springs Zone.

I believe there is a better way that does not involve changing SOS. It would be elective by the property owners. It would restore highest and best use of and and increase tax revenue.

That strategy would allow low acreage property owners (< 3 acres) to develop under SOS or elect to voluntarily place an additional property tax of their property in lieu of complying with SOS. The additional tax burden would be negotiated between the property owner and the City.

One of the major impediments to redevelopment for owners of small parcels is the significant front end costs along with others mentioned above. The purchase of water quality mitigation land required by the City is one such expense. This alternate strategy would allow the owner to pass through to future tenants the additional property taxes as part of their triple net lease agreements.

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This is a interesting idea and the simplicity of it is enticing, but to apply it uniformly across the City makes it unsupportable. There are certain highly sensitive areas where impervious cover is both particularly detrimental and difficult to mitigate even though the land may be desirable enough to those who can afford to pay whatever additional fees are incurred (e.g., West Austin hills over recharge zone and at the top of watersheds; floodways that may be near otherwise desirable water features.)

Agree with other comments that the success of the proposal is too dependent on setting just-the-right fee (which probably varies by area) as well as collaboration with AHJs in neighboring municipalities and unincorporated areas such that unintended sprawl isn’t the result.

A base ‘by right’ amount of impervious cover by zoning district (with some more restrictive overlays) and then an ability to ‘buy’ additional impervious cover in desired growth areas only is probably a better approach.

Not being sure if this is like Brexit, and we only get one chance, I voted (so far) in favor of what @carsonjd rightly pointed out is an imperfect proposal. Suggestions that impervious cover restrictions should be relaxed and runoff be a priority appear to be shared beliefs among "all’, how it is packaged needs some work. It is an important shift in thinking worth pursuing and promoting it may be my favorite of the 9 resolutions.

Let me ask the question - why tax impervious cover, especially the portion used for buildings? Maybe tax single story buildings or surface parking, or high cover per unit, but dense housing? Maybe if for additional revenue or to mitigate over reliance on property taxes? Both could be right answers.

It seems like the devil is runoff, and as rightly pointed out in SOS and upstream watershed areas it may well be appropriate to look at the issue differently. That could help protect the green belt and provide even further incentives towards compact and connected. I don"t see us controlling sprawl outside our boundaries, best hope may be for jobs closer to or in those communities. It"s happening partly already due to Austin affordability.

Like the SOS ordinance it would only apply in the Barton Springs Zone. It would not be applied across the entirety of the City but only in the BSZ and only for NON-compliant existing commercial properties and an alternative to SOS or the rules established within the Redevelopment Ordinance.

Be mindful that these small parcels perpetuate not only pollution but legacy uses and architecture that do not reflect current best and highest use. Therefore they are under performing with respect to generating tax revenue as well.

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Taxing impervious cover is better than the alternatives because it’s the thing that creates the externality that causes the most problems for others. Development would naturally occur both wider and higher in higher-value parcels and stay lower in lower-value parcels if we established a simple price for impervious cover rather than an arbitrarily low cap.

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