Urban Design and the RMA: Urban Planning v Urban Design

Further thoughts on urban design under the RMA.

It is important to distinguish urban design effects from other effects. Otherwise there may be double counting. For example, there is a big overlap between urban planning and urban design. Are urban design effects just urban amenity effects? There is also overlap with landscape and visual assessment, In this blog, I want to look at urban planning and urban design. 

There are different ways to conceptualize this overlap:

Urban design has been described as second order design. First order is buildings or spaces. Third order is (spatial) planning. Urban design is said to be the link in between these two orders, finding first order designs that help fill in the third order outcomes. Some urban designers will baulk at this distinction, as urban design works across all spatial scales.

Another way to look at the issue is that urban design follows a different process to urban planning. Urban planning follows a structured process of identifying outcomes, options analysis, making trade offs and selection of appropriate set of tools to achieve the desired outcome.  Urban planning attempts to be rationale. It is by its nature synoptic (it tends towards the large scale). The end product tends to be a bunch of processes and procedures against which individual developments are judged.

Urban design in contrast could be said to be more place-based and more iterative in its approach to bringing together a range of outcomes for an area or site.   The design process can be a bit irrational and improvised. There may be no universal sequence of stages – analysis, design and implementation are contemporary and inextricably linked. The end product can be a resolved 'plan' for an area - the masterplan or structure plan.

This process type distinction may be valid, but it doesn't really help with distinguishing urban planning from urban design effects. The idea that urban design may operate at a different 'level' to that of urban planning is more useful. But how to describe this in terms of RMA effects?

To  start with, urban design can be said to concentrate on the quality and functionality of the built environment. It is clearly not about management of the natural environment, or about infrastructure planning, for example, although these matters are relevant matters. Urban planning could be said to sit above and span across these different 'inputs'.  Moving on from that, clearly urban planning has a focus on urban quality, but is perhaps more directed at the basic building blocks of urban quality, rather than place-based responses. 

Urban design brings in a strong element of the human response to new and modified urban environments. Perhaps this is the strongest distinction between urban planning and urban design - urban planning needs to take a long term (intergenerational) view of the management of urban resources; urban design is more about the day-to-day response and interplay between people and the built environment.   

Matthew Carmona has suggested in Place Value: Place Quality and its Impact on Health, Social, Economic and Environmental Outcomes (see note 1) that it is possible to envision different urban qualities as sitting on a ladder that climbs from:

1. those place qualities to be avoided when shaping the built environment (because of their very possible negative impact on place value); 
2. those place qualities which are fundamental and which should be required as a means to maximize place value through good design.
3. place qualities that are strongly associated with the delivery of place derived value of all types (and which should be the aspiration of built environment policy and development-related decision making). 

I think the list of things to avoid and those that are essential (number 1 and 2 in the list above) are more to do with urban planning, rather than urban design.

Starting with the qualities that are fundamental:

• greenness in the built the environment (notably the presence of trees and grass, water, and open space ‒ the latter if of good quality); 
• a mix of uses (notably the diversity of land uses within a neighbourhood); 
• low levels of traffic; 
• the walkability and bikeability of places (derived from their strategic street-based connectivity and the quality of the local public realm); 
• the use of more compact (less sprawling and fragmented) patterns of development; and 
• ready convenient connection to a good public transport network. 

And the qualities to be "avoided":

• car dependent and extensive forms of suburbanization;
• relentlessly hard urban space (absence of local green space);
• too much very local permeability;
• the presence of rear parking courts and other segregated areas;
• poor maintenance / dilapidation (including of green spaces);
• a sense of overcrowding in residential areas;
• the presence of unfavourable food stores; and
• the impact of roads with higher traffic loads and speeds, wider carriageway widths, or which are elevated.

Im not quite sure what unfavourable food stores are (too may fast food outlets?)  while some of the effects are more operational rather than layout and design (such as poor maintenance).

Urban design can then come more strongly into play in the third sets of qualities, as described as follows:

Next there is a strong positive association between place derived value of all types and fifteen often less tangible, sometimes subjective, and generally more difficult to measure qualities of place. Whilst the evidence on each of these remains powerful, it is not definitive, in the same way as it is for the qualities already discussed. Partly this seems to be because the more ‘difficult’ nature of these qualities makes researching them more challenging, and so there is often less research available on which to make a definitive assessment. There are also greater challenges in specifying exactly what quality means in these areas, making the evidence that is available more equivocal.

These qualities include:

• visual permeability;
• sense of place (distinctiveness);
• pedestrian scale (of streets and buildings);
• façade continuity;
• natural surveillance (the creation of defensible space);
• presence of street level activity / background movement;
• good street lighting;
• a denser street network (urban grain);
• low traffic speeds;
• low neighbourhood noise;
• presence of attractive / welcoming / comfortable / adaptable public spaces;
• positive (sociable) public/private threshold features;
• integration of built heritage;
• integration of natural features and a diverse ecosystem; and
• perceived architectural quality and beauty generally in the built environment.

Carmona notes that whilst some of these qualities, for example façade continuity or traffic speeds, are relatively easily specified, most need more careful interpretation. In his words, they are therefore likely to be ‘aspirational’ rather than required qualities. In RMA terms they may be qualities that need assessment as to the degree to which, if they are missing or only partially applied in a development, adverse  'spillover' effects may arise.  

Interestingly, he has a set of qualities that are not so certain as to the link to place quality. These are:

• different architectural styles (about which the evidence is simply unclear).
• higher versus lower densities of development (where within the health research, and with regard to sociability versus perceived crime, the evidence conflicts).
• extreme densities (where conflicting evidence is apparent relating to carbon reduction, social welfare and ecological richness).
• high-rise living (where the evidence is unclear, although tending to warn against families living in such circumstances).
• street length and pedestrian connectivity (where divergences are apparent within the evidence on health versus crime).
• cul-de-sacs (where, within the evidence on crime and safety and with regard to property value, sociability and children’s play, conflicts are apparent).
• vehicle / pedestrian separation (about which the evidence is weak and indecisive).
• use of shared spaces (where conflicts are apparent, particularly with regard to the evidence on actual and perceived safety).
• the economic impact of the proximity of retail to residential properties (about which conflicts exist on the relative size and impact of negative externalities sometimes associated with local retail)

Some of these qualities are relevant to urban design principles. I guess what is important is that these sets of qualities need to be applied with a high degree of judgement. 

Note 1: Place value: place quality and its impact on health, social, economic and environmental outcomes. Matthew Carmona. Sourced from  https://www.tandfonline.com/doi/full/10.1080/13574809.2018.1472523

Urban design, mental health and the RMA

Back to urban design and the RMA.

Last blog on the topic I looked at the economic rationale for urban design controls. Some helpful ideas were thrown up, but the issue of how to rate the scale and significance of 'effects' remains.

Time to switch tack and look at the psychological rationale for urban design. Social and mental well being are important concepts these days. These are issues to do with the ability of people to function in an urban environment. At base they are more to do with basic liveability than managing a negative spillover effect on an adjacent activity.

Cities may be bad for your mental health. One discussion puts it as follows (note 1):

The urban setting can affect people in two key ways: increasing stimuli, and stripping away of protective factors.

Overload: People who live in the city experience an increased stimulus level: density, crowding, noise, smells, sights, disarray, pollution and intensity of other inputs. Every part of the urban environment is deliberately designed to assert meanings and messages. These stimuli trigger action and thought on a latent level of awareness, and become more potent as an inability to ‘cope’ sets in. This can have the effect of overload: increasing the body's baseline levels of arousal, stress, and preparedness, but also driving people to seek relief: quiet, private spaces; over time this urge may evolve into social isolation associated with depression and anxiety, and also forms the basis of the ecological hypothesis of schizophrenia.

Erosion of protective factors: People who live in the city may find that they have less access to the factors that are protective for good mental health than those in rural areas. For example, they may have diminished access to nature, fewer opportunities to integrate exercise as part of their daily routines, and reduced leisure time as increased time is spent at work and commuting around the city. People may find themselves feeling unsafe, having less privacy, and even less sleep, due to factors like crowding, light, noise and stress. This may particularly be the case as urban dwellers may be reluctant to engage in social interactions, to avoid overstimulation, due to safety concerns, or because of the reduced likelihood of future relationships with each individual they encounter.  As these protective factors erode, people become more vulnerable to developing mental health problems.

So is urban design bad for your health?  No, if anything, urban design can help reduce the negative stimulus and improve the protective factors.

An interesting book on this topic is: Headspace. The Psychology of City Living. Dr Paul Keedwell.

As with much of environmental psychology, the basic point of the book is that us humans are not necessarily well set up to deal with urban environments, given our long evolutionary period as hunter gathers. His main point could be:

When the built environment of the city departs too much from the natural environment of our distant ancestors it becomes an instinctive, unconscious threat to our mental wellbeing.

This doesn't mean that cities should have lots of trees and open grasslands which we can roam chasing wild animals and collecting nuts and berries. Rather, it is the qualities or characteristics of the environment that we are adapted to that are important. Many of the points made about the effects of the built environment on mental well being resonate strongly with urban design ideas. Some things I found interesting:

Our homes should come with a garden or view of a green space, as we are so attuned to being in a natural environment

The survival instinct for refuge is balanced with the need to have a good view of the surrounding landscape. Living rooms should balance the two – a view out but also a refuge. Windows should be tall, but not too big, and in proportion to the walls, ceilings should not be too low. Buildings with high ceilings are inviting and inspiring.

We like some complexity and texture on the façade of a home and don’t really like featurless monochrome brick with no balconies and decorative details to break up the frontage. What we find satisfying about natural landscapes is detail and variation, and look for these qualities in buildings.

The silhouette shape and overall structure of the buildings main surfaces is less important than the amount of decoration on the surface and the detail in the trim around windows and doors.

Experience suggests that the need for security, visual interest and issues of distinctive identity extend beyond the home. Good neigbourhoods have social capital and cultural capital. We are a tribal species. A sense of ownership and history is important. The more distinctive a place by virtue of its local history the more likely the local community will become attached to it, with feelings of connectedness that we all crave in order to live happy lives. A close knit neighbourhood acts as an antidote to the sometimes uncaring wider cityscape.

Being near a thriving mainstreet is crucially important, with a variety of businesses, lots of greenery, visual interest and walkable streets, not drowned out by heavy traffic

A degree of legability to a city environment is important to our sense of safety. Complexity in terms of trees and contours might give us more options for foraging and for shelter. But if we cannot immediately understand our environment we can’t do a risk assessment to make sure we are safe from predators – can we see them approaching, and can we escape easily?

These basic points are echoed in other advice, for example the following is a web site directed at mental health and urban design. See https://www.urbandesignmentalhealth.com/how-the-city-affects-mental-health.html

Mental health and wellbeing is within the remit of urban planners, managers, designers and developers, so mind the GAPS:

Green places – There are important relationships between accessible green spaces and mental health and wellbeing. Access to natural settings in neighbourhoods and in the course of people’s daily routines is likely to improve and maintain mental health and wellbeing.

Active places – Positive, regular activity improves mood, wellbeing and many mental health outcomes. Embedding action opportunities from active transport to outdoor gyms into places helps integrate exercise, social interactions, and a sense of agency into daily routines.

Pro-Social places – Urban design should facilitate positive, safe and natural interactions among people and promote a sense of community, integration and belonging. This includes potentially vulnerable groups like refugees, migrants, young and older people, with multi-faceted engagement from passive observation to active participation. Creating interesting, flexible public places should involve citizens at each stage of design and development.

Safe places – A sense of safety and security is integral to people’s mental health and wellbeing. Urban dangers include traffic, getting lost, environmental pollutants, and risks posed by other people. Appropriate street lighting and surveillance, distinct landmarks, and people-centric design of residential, commercial and industry routes are important. A balanced approach is necessary: a safe environment improves accessibility but risk-averse city design can reduce action opportunities and people’s sense of agency and choice.

So what does that all tell us about urban design effects?

1. Effects go way beyond managing adverse effects
2. The effects of poor design can be subtle in their expression 
3. Things like active street frontages that might be judged to be 'nice-to-have' things are actually very important
4. It is hard to judge the scale of an effect. Either the quality is there or it is not, trying to work out what is a minor effect versus a significant effect is not easy.
5. Cumulative effects are critical. Each little bit of the city is important.
6. What about personal choice? People don’t have to live in or walk past a place with no green space, with poor design? But many people have limited economic means and don’t have a great amount of choice. 

None of the above sits very happily with the RMA.

Note 1. Sourced from: https://www.urbandesignmentalhealth.com/how-the-city-affects-mental-health.html

Urban design and the RMA (4)

Urban design: the economic approach to defining effects

I'm on a one person mission to better define urban design effects under the RMA. So far I have:

1. discussed effects ratings and their purpose under the RMA
2. tried to develop an 'effects equation'
3. asked: is urban design normative or positive?

Now the obligatory economic rationale for intervention relating to urban design outcomes. Having some understanding of the rationale for intervention is obviously important in developing a framework for managing that intervention. Many people like the idea of some sort of 'market failure' as being the basis for intervention.

Commonly, the basic rationale for a degree of public control over buildings and development relates to managing negative externalities. This is where MfE's helpful report on the Value of Urban Design starts. There are negative externalities of poor design. These affect the public realm, as well as adjacent sites.

Negative externalities occur when production and/or consumption of goods (such as buildings) impose external costs on third parties outside of the market for which no appropriate compensation is paid. This causes social costs to exceed private costs. But we have to be very careful how we define these externalities. Is the effect of an ugly building beside a nice building a negative externality? Or is it just part of urban life?

Rather than being a negative thing, is urban design just about good things (including positive externalities), and by implication things where there maybe a financial incentive for designers and developers to add good things into their designs, in which case there is no need for public intervention?

If urban design is all just human behaviour, then won't people vote with their feet, avoiding areas that are poorly designed and flocking to areas and places that are well designed, and from  this process of selection,  their money and buying power. As such, is there an incentive for developers and businesses to promote good design?  By why so much bad design if there is so much value to be extracted by good design? Is it that people have a high tolerance of bad design?

The MfE report on urban design also mentioned inconsistent time preferences. Developers may have shorter time horizons (higher 'discount rates') than the community as a whole (e.g. short-term profit to developers versus long-term health benefits to society). This means that the market will tend to provide a level of urban design than is not socially optimal.

These points provide a helpful starting place. But somehow urban design is more complex than this. While concerns about poor quality design on a next door site driving down property values is a common basis for communities to call for urban design, to me the real issue relates to the importance urban design plays in supporting a functional public realm. The importance of the public realm to well functioning cities seems under recognised in most urban economic analysis. The public realm is not a tradeable good, it has a value but no price. It is not subject to the laws of demand and supply.

Many of the dis-benefits of poor design are less tangible social, environmental or well being impacts affecting a range of parties, over a long period of time. They tend to be second order effects (if there is such a term). Adverse effects of bad design are often  incremental and cumulative, they are not necessarily all obvious 'blots on the landscape'.

If we take Jayne Jacobs and her prescriptions in The Death and Life of Great American Cities as a starting point, then we have the following four basic ingredients to generate (in her words) urban vitality:

1. The district must serve more than one primary use, and preferably more than two.
2. Most street blocks must be short.
3. Buildings must be mingled in their age, condition, and required economic yield.
4. A dense concentration of people.

I think it is reasonable to say that the third and fourth conditions are enabled conditions, in that there are characteristics that need to be allowed for and encouraged. The third condition does not mean heritage protection, although that may be a component. I think what Jacobs  meant was that redevelopment should be an incremental, even scattered process, not a concentrated or cataclysmic process (as was much public urban regeneration schemes of the day). In contrast, short blocks and mixed uses are not necessarily elements that are always provided.

Jayne Jacobs did not stop with the four characteristics. She also (famously) referred to the need for ‘eyes on the street”.  To her, vital, safe streets had the following elements:

"First, there must be a clear demarcation between what is public space and what is private space. Public and private spaces cannot ooze into each other as they do typically in suburban settings or in projects.

Second, there must be eyes upon the street, eyes belonging to those we might call the natural proprietors of the street. The buildings on a street equipped to handle strangers and to insure the safety of both residents and strangers, must be oriented to the street. They cannot turn their backs or blank sides on it and leave it blind.

And third, the sidewalk must have users on it fairly continuously, both to add to the number of effective eyes on the street and to induce the people in buildings along the street to watch the sidewalks in sufficient numbers. Nobody enjoys sitting on a stoop or looking out a window at an empty street. Almost nobody does such a thing. Large numbers of people entertain themselves, off and on, by watching street activity.”

So I think we can translate these ingredients into the following core urban design elements:
1. The nature and extent of the public realm network
2. The range of activities that border that network (the density and mix of uses)
3. The quality of the public private interface of that network.

If we look at these ingredients in turn, then a somewhat more complex rationale emerges as to the reason for intervention.

Public network

The nature and extent of the public realm network is important to functioning of urban areas. Cities need lots of routes and linkages.  Short, interconnected street blocks help with walkability and access to public transport and local services. They promote health and well being through active transport. They generate street-based activity which helps with a sense of safety and 'connectedness' .

Jayne Jacob’s principle of short blocks is the common urban design principle of promoting connectivity and permeability. The UN-Habitat’s Global Urban Observatories Unit report on Streets as Public Spaces and Drivers of Urban Prosperity argues that streets should be counted as public space alongside leafy parks and landscaped plazas. Together, they should make up 45 to 50 percent of a city’s land area, with 30 to 35 percent of the area occupied by streets and 15 to 20 percent open space. “If less than 30 percent of the land of the city is dedicated to the street pattern, it’s a huge error,” Beside the economic value of streets on the land market, streets have an economic and social value related to productivity, infrastructure, quality of life and social inclusion.

The argument for intervention around the network is that as land increases in value, then there is a tendency for less of that land to be devoted to public space. In economic terms, this conception of the public realm could be thought of as an inferior good. A normal good is a good that is in greater demand as incomes rise. An inferior good sees the opposite outcome – demand shrinks as incomes rise. In a city, as incomes and land values rise, there is an incentive for development to provide less and less public space as this has a bigger and bigger cost. Furthermore, the value added by streets to the value of plots and buildings are not well factored in the land market. Neither real estate developers nor land owners are willing to appreciate the economic value of streets against its social value.

In this conception, the street should not be considered as an inferior good, rather the street should be considered as a normal economic good if not a superior good that should be allocated more share in the expansion of cities.

Mixed Uses

Diversity of activities along the main routes of the public network is crucial to urban outcomes. Here you might think that a removal of single use zonings would enable and allow for diversity of activities to flourish. There is no need to mount a case to intervene to support mixed uses and diversity of activities.  But why are mixed uses so rare in cities, especially the bits built post war?
Jacobs noted that diversity tended to destroy itself, particularly as one use becomes dominant and bids up rents to the point where other uses flee.  This results in a single-use office district, restaurant strip, etc. Density and diversity of activities can also be related to the diversity of the building stock. Mixed uses need a range of cheap and expensive premises that are big and small. Mixed uses also often take a while to get established. A catchment of people needs to be built up first, then the service-based activities start to flourish, but short term time horizons mean that developers may favour the residential phase.

One of Jacob’s cures for self destruction of diversity was to zone large areas for diversity. However this is not in the sense of requiring a set mix of activities. Rather it was first to zone for a diversity of building stock. This is in terms of building ages and building sizes.  She cites the example of a park having lower buildings on one side to let in sun, but also to offer a choice compared to taller buildings on other sides. This in turn creates opportunities for different types of mixed uses. Elsewhere she mentions the importance of having many old buildings to provide cheaper space for new activities to get established. She acknowledged that maintaining a diversity of building stock would require some sort of financial acknowledgement. Hence perhaps why the idea never took hold. It also requires some form of gradual process of redevelopment of an area, not a ‘catastrophic’ replacement of buildings (and hence her call for a mix of old and new buildings).

The other cure was to have lots of opportunities for mixed uses to locate in a city. If one neighbourhood sees a loss of diversity, then provided the displaced activities had somewhere else to go to, then the city as a whole does not see a negative effect.

Whether the self destruction of diversity provides a rationale for intervention is difficult to say. One study (The Impact of Mixed Land Use on Firms An empirical investigation on commercial property transactions, Francis Ostermeijer July 2016) suggests that in a rational market, one would expect that firms involved in mixed land use patterns are likely to relocate until the marginal benefits and costs of relocation are equal. This implies a degree of natural mixing. "In reality however, this rationality assumption may not hold. It is perhaps more likely that there will be a sub optimal provision of mixed land uses. Therefore, land use regulation may be warranted in order to encourage a balanced mix of uses in order to maximise the net social benefits from mixed land uses".

For example, from a developer and landowner’s perspective, horizontal mixed land uses are preferable to vertical mixed land uses. This may be because the positive externalities from a diverse composition of land uses on a street such as pedestrian safety, higher aggregate demand and a better distribution of demand may not outweigh the costs imposed on individual activities in a mixed use building due to concerns over less privacy, increased security risks, less prestige and greater uncertainty of leasing of space when in a vertical mixed use situation.

Another way to look at the issue of under supply of mixed uses is that they are a merit good. A merit good is a good where consumption of the good generates an external benefit to others, from which society gains, but that benefit is unlikely to be known or recognised at the point of consumption. Given that decisions to consume are driven by self-interest, it is unlikely that this external benefit will be taken into account when the consumer of a merit good evaluates its worth. As a result merit goods are often  relative to their wider benefit.

So maybe there is a rationale for seeking mixed uses. But is that rationale based on finding an incentive or some form of support for greater provision of mixed uses, rather than a sanction?

Quality of the public private interface

The public realm is more than just the network of public streets or areas of public open space. The public realm extends to the buildings, activities and private spaces that front onto these areas. The quality and functionality of public spaces is very dependent upon what fronts them; how buildings interact with public spaces. No amount of flash landscape design can lift a street or public space if it is surrounded by dull buildings.  The public realm can also be described as the spaces within a site that the public can access without having to ask permission, such as laneways. But it is the areas owned by the public which are critical to the social and economic success of cities. Nice buildings fronting a street or open space does not automatically mean that the road or open space will deliver benefits. People using the space generate the value.

The public realm of a city is a ‘public good’. Public goods are goods that have the following characteristics:

• Non-rivalry: This means that when a good is consumed, it doesn’t reduce the amount available for others.
• Non-excludability: This occurs when it is not possible to provide a good without it being possible for others to enjoy.

You can quibble if a road or open space is non rivalrous. At some point, one more person added to a street or open space may make that place overcrowded or congested. Technically a road or open space is a quasi public good.

The problem with public goods (quasi or not) is that they have a free rider problem. This means that it is not possible to prevent anyone from enjoying the good, once it has been provided. Normally this creates a problem of payment and overuse:  there is no incentive for people to pay for the good because they can consume it without paying for it. People can over consume public resources – the tragedy of the commons.

The public-private interface is a bit different. It is not about the over use of the public road or public space.  Rather there can be a natural tendency for private development to ‘sponge off’ a high quality public realm, rather than contribute to that realm.  For example, I will erect a larger fence across the front of my property to keep me safe and private, but I will still wander down the road in the evenings enjoying looking at the various front gardens and feeling safe because of the passive surveillance offered by all the housing which has windows to rooms that overlook the street.

Back  to effects rating

Back to the question of an effects rating. What does the above tell me about urban design and effects? That it is not straight forward? That is hardly a revelation.

The above provides a framework by which effects could be organised or grouped, but does it help with determining the magnitude or persistence of the effect? Is my effects equation up to the task? Perhaps not.

What the above does suggest is that rather than be some sort of  minor to major negative externality rating, any urban design rating framework needs to be more focused on the support or not for a well functioning public realm.

Urban design effects and the RMA 3

More on urban design effects and the RMA. I'm trying to work may way through some sort of urban design 'effects' rating system.

So far I have tried to understand what a rating system needs to do;  how rating effects contributes to procedural and substantive decisions under the RMA. Now the meaty part – what are urban design effects in terms of the RMA? Lots to work through here.

Looking at how RMA plans 'codify' urban design may not be the best place to start at trying to understand urban design effects. RMA plans tend to pick up on a sub-set of urban design. But equally many urban design texts and guides can be so wide ranging as to their definition of urban design that trying to work out what an effect is, is not easy.

So I need to take a different tack.

Somethings to address are:

• Is urban design normative or positive?
• If positive, then in what way does urban design affect the environment? 
• Are urban design effects a positive or negative externality?
• Urban planning versus urban design?
• Whither the 7cs of the NZ Urban Design protocol?

Normative or positive?

Why start here? Perhaps the most basic assumption to be made is that urban design effects can be reliably, objectively measured in someway. Is urban design  just a bunch of ideas as to how the built environment should be, with those ideas varying from urban designer to urban designer? Positive statements must be able to be tested and proved or disproved. Normative  statements are opinion based, so they cannot be proved or disproved. Normative statements do not really help with constructing a robust rating system.

Having the word 'design' in urban design lends urban design towards the normative end of the spectrum. Design suggests a creative endeavour, perhaps something aimed at making a 'bit of a splash'.  The other interpretation of 'design' is the sense of something of standard form or function that is shaped or moulded to fit specific circumstances.

I think urban design is increasingly grounded in research and observation. It may have started out as a bunch of thoughts and guesses about the interaction of people with built environments, but things have moved on. There is the 2005 MfE report on the value of urban design. This is still a good report. People like the old UK CABE (Commission for Architecture and the Built Environment) referred to the benefits of urban design as providing ‘value’ in terms of things like:

• Exchange value: parts of the built environment can be traded;
• Use value: the built environment impacts on the activities that go on there;
• Image value: the identity and meaning of built environment projects, good or bad;
• Social value: the built environment supports or undermines social relations;
• Environmental value: the built environment supports or undermines environmental resources;
• Cultural value: the built environment has cultural significance.

More recently M Carmona in a paper called: “Place value: place quality and its impact on health, social, economic and environmental outcomes” (note 1) suggests that a different way of thinking about urban design benefits  is more straightforwardly the degree to which the different qualities of the built environment impact, either positively or negatively, on different public policy goals. Things like public health, public safety and promoting social interaction are all basic public  ‘goods’ or services that economies and communities need for them to operate successfully. Urban design and the built environment can and does influence the nature and extent of relationships between people and these public goods. The built environment might get in the way of a positive relationship, it can also accentuate a negative relationship. The built environment can also enhance these relationships.

After reviewing over 200 studies on the links between the built environment and public policy goals Carmona concludes that there are strong links between built environments and health and safety, as well as supporting economic exchange and improving the environment.

Now that is all well and good, but it might be said that urban design is not a proven set of facts or theories about how the built environment affects safety, for example. There is no theory in the sense that we can say with certainty: do x and y will result. It is not possible to be so assured as to the link between cause and effect. The above studies show a correlation between good and bad urban design and many positive and negative outcomes. But is there a causal link?

After all human beings are involved. Someone penned the following thought:

As I walk I react to the scale of a building in relation to the scales of others and to that of my own body. In all their proportionate interrelationships, heightening my awareness of self in space. To make my way toward my destination I draw geographic inferences and impose cognitive maps that orientate myself in, and make sense of, the structures through which I move, Drawn and reassured by the vitality on the street, I come out to join that urban commerce and thereby contribute to my own presence to the city’s life. The landscape features I pass become meaningful to me through their capacity to express cultural references, whether local or foreign. Any my determination to continue walking depends on how well the landscape responds to my flagging strength, my desire for shelter, my need for rest, and my wavering curiosity. 

Carmona contends that it has been found that urban design is at least in part pseudo-scientific. This does not mean that urban design rests on a ‘foundation of nonsense’, but a foundation of untested hypotheses, or individual scientific findings that are not scientifically incorporated into the urban design corpus of knowledge.

That urban design can be classed as ‘pseudo scientific’ is not fatal. Jayne Jacobs ends Death and Life of Great American Cities with a chapter on how cities are systems of organised complexity. As such they cannot be analysed by standard scientific techniques (two variable problems). There are many variables in cities which interact and interrelate, many of which are not subject to proven theories of cause and effect.  It is more a matter of likelihoods and probabilities.

She explains some tactics to analyse organised complexity:

• Detail – identify a specific factor and then painstakingly learn its intricate relationships and interconnections. Then move onto another factor
• Look for leverage – seek ‘unaverage’ clues involving very small quantities which reveal the way larger and more common quantities operate
• Processes – cities are always evolving – there is no equilibrium, so any activity or building or space must be placed in some sort of continuum or timeline. Focus on the catalysts that arrest one phase and start another
• Work inductively – reason from the specific to the general.  This helps to avoid seeing cities in the abstract. 

Urban design does concentrate on details, like where the front door is. It does refer to both the exceptional and the normal. Urban design looks at the urban environment not in the abstract, but in specifics.

But is the lack of a scientific base to the understanding of urban design effects an issue? In a world of evidence driven policy, then maybe and maybe not.

Maybe not because much of resource management is about dealing with predictions and uncertainties as to future effects in the absence of complete knowledge. As we all know there is a huge area of opinion and judgement involved in many areas of urban planning and resource management.  Here, probabilities of claimed effects are important. How certain are the links between cause and effect of many urban amenity concerns?

This has been called post-normal science. This is where people involved in unresolved issues hold strong positions based on their values, and the science is complex, incomplete and uncertain. Diverse meanings and understandings of risks and trade-offs dominate.

In a similar vein, given uncertainties, an Environment Court judge has suggested that the probabilities of effects be considered in terms of:
• Confidence in facts
• Likelihood of predictions.

But maybe the lack of a strong theory that has stood up to scrutiny (not be falsified) is an issue, mostly because of the human behaviour aspect of urban design.  The social aspect of  built environment effects may mean that adverse urban design effects need to get to a ‘significant level’ (whatever that is) before management and mitigation of them can kick in. Should the bar for action be a bit higher than for effects on the natural environment, for example?

Note 1: http://placealliance.org.uk/wp-content/uploads/2019/01/2018-June-12-Journal-of-Urban-Design-Place-value-place-quality-and-its-impact_MC.pdf

Effects, urban design and the RMA: 2

I'm on a (one person) quest to better define urban design effects as part of RMA processes. I have started by looking at how effects might be defined, before looking at urban design effects. I ended my first post on the topic with the following effects 'equation':

The scale of an effect is a combination of:

Persistence of effect * magnitude of effect * extent of the effect * probability of the effect * consequence to receiving environment * possible mitigation (reduction) * plan weighting.

I am not sold on the above equation, but it is a start.

If you think the above is a bit complex, then look at the following. This is from Department of Conservation’s guidance on policy 13 of the New Zealand Coastal Policy Statement (which in turn is drawn from a regional policy statement).

The following guidance aims to help with determining the extent to which an adverse effect is ‘significant’.

Status of resources: The importance of the area—locally and regionally. (Effects on rare or limited resources are usually considered more significant than impacts on common or abundant resources).

Proportion of resource affected/area of influence: The size of the area affected by the activity will often influence the degree of impact (i.e. affecting a large area will generally be significant). Affecting a large proportion of a limited area or resource will tend to be significant.

Persistence of effect: The duration and frequency of effect (for example, longterm or recurring effects as permanent or long-term changes are usually more significant than temporary ones. The ability of the resource to recover after the activities are complete is related to this effect).

Sensitivity of resources: The effect on the area and its sensitivity to change. (Impacts to sensitive resources are usually more significant than impacts to those that are relatively resilient to impacts). Reversibility or irreversibility: Whether the effect is reversible or irreversible.

Irreversibility will generally be more significant (depending also on nature and scale), and reversibility the converse.

Probability of effect: The likelihood of an adverse effect resulting from the activity. Unforeseen effects can be more significant than anticipated effects. (Adopting a precautionary approach may reduce the likelihood of adverse effects occurring).

Cumulative effects: The accumulation of impacts over time and space resulting from the combination of effects from one activity/development or the combination of effects from a number of activities. Cumulative effects can be greater in significance than any individual effect from an activity (for example, loss of multiple important sites).

Degree of change: The character and degree of modification, damage, loss or destruction that will result from the activity. Activities that result in a high degree of change are generally more significant.

Magnitude of effect: The scale and extent of possible effects caused by an activity (for example on the number of sites affected, on spatial distribution etc). Activities that have a large magnitude of effect are generally more significant.


I think this list can be re arranged to match my equation, as follows:

DM rating	DoC
Persistence	Persistence of effect:
Magnitude	Magnitude
Extent	Proportion of resource affected/area of influence
Probability	Probability of effect
Consequence	Degree of change Irreversibility Sensitivity of resource
Possible mitigation
Plan weighting	Status of resources:

The DoC list doesn’t have mitigation in it. It does have cumulative effects in it. More on that below.

As another example, Environmental Impact Assessment (which is where the idea of Assessment of Environmental Effects comes from) can have a fairly complex list of things to look at when considering impacts. For example:

Characteristics of Impact:
• the extent of the impact (geographical area and size of the affected population);
• transfrontier impact;
• magnitude and complexity of impact;
• probability of impact;
• duration, frequency and reversibility of the impact.

Transfrontier impacts refers to whether the impact crosses country borders or other boundaries.

Again some similarities come through in terms of the dimensions of an effect.

Once the components of effects has been considered, how do you express the product of the equation? I wonder if the scale for urban design effects should be related to people’s reactions to or acceptance of change to an urban environment, given that cities are all about people, but also constant flux and change. For example, effects are:

1. Not discernible
2. Negligible
3. Tolerable
4. Undesirable
5. Detrimental
6. Intolerable.

These might be described as follows:

Overall rating	Description
Not discernible	Within the normal range of effects / rate of change as currently experienced, generally not perceptible
Negligible	Effect may be noticed against 'background levels', but would be so small or unimportant as to be not be worth addressing. It would not change day to day activities in any material way
Tolerable	Effect would be noticed and may change behaviour / routines, but within the ability of people to adapt. The effect may be bearable
Undesirable	Effect would be noticeable and negatively  impact on people’s day to day routines. It would be objectionable or unpleasant. The effect might be able to be mitigated or potentially traded off for other much bigger benefits
Detrimental	Effect would be visible and be felt. It would be harmful or damaging. People would need to be take deliberate action to avoid the effect which would reduce the overall utility of the environment to support urban activities
Unbearable	Level of effect is excessive and would negatively impact on a wide range of people and lead onto other spill over effects that cannot be managed. The effect would be calamitous and destructive to an urban environment.

The above categories of effects can be related back to the threshold / procedural tests of the RMA as follows:

Rating	Degree of ‘minorism’	Degree of significance
Not discernible	Less than minor
Negligible	Minor
Tolerable	More than minor
Undesirable		Significant, but maybe 'tradeable'??
Detrimental		Significant, best avoided
Unbearable		Significant, avoid

Having said all that, I am not convinced that the above deals with the issue of small, incremental changes to urban areas. Many urban design matters involve small scale changes to the built environment, and most often are not changes to a highly valued environment. One tall fence on the front boundary of a 'normal' residential site might not seem so bad, a whole street of high fences is a problem, but getting from one to many high front fences usually involves numerous small steps. Is the first tall fence an 'unbearable' effect?

As a different example, the area or number of people affected may be relatively small, with only a minor portion of an urban area subject to the effect. A formula which talks about nature and extent of change might imply that changes that affect 100s of hectares are much more important than changes that affect one or two sites. As a result the small changes should get a low 'relative' impact rating.  But of course only one in twenty cases may affect 100  hectares, but 19 cases may affect 5 sites each.

This is the cumulative effects issue; an issue which goes round and round without resolution.

One guide says that cumulative effects become significant when these impacts on the environment:
• “occur so frequently in time or so densely in space that they cannot be assimilated or
• combine with effects of other activities in a synergistic manner” .

In other words, cumulative effects may be additive (accumulate) or synergistic (amplify other effects). Someone has also pointed out that cumulative effects could also be neutralizing (the effects cancel each other out). The issue with accumulative effects is their frequency.

It is the accumulative form of cumulative effects which are perhaps most relevant to urban design. It is common for assessment guides to note that there are thresholds where additional (small scale) disturbance can result in significant deterioration of resources or ecosystems. Cumulative effects become apparent when such thresholds (tipping points) are breached.

But if the effect is at the start of the sequence of potential repetitions, and no threshold has been reached, then a cumulative effect has not yet technically occurred. Even if there is a clear sequence occurring, identifying the tipping point is not easy, and is often only apparent in retrospect.

Cumulative effects can be related to the concept of the "tyranny of small decisions".  Overtime, big changes can occur as a result  of many steps, each small in their individual size, time perspective, and in relation to their cumulative effect. In economic terms, the tyranny of small decisions means that a series of apparently free, individually welfare-maximizing 'purchase' decisions can so change consumer tastes and the context of subsequent choices that desirable alternatives are cumulatively and irreversibly destroyed.

There is no straight forward antidote to the tyranny of small decisions, except to say that someone needs to keep the bigger picture in mind.  But just saying that cumulative effects should be taken into account in the effects equation doesn't really help much.

Plan weighting maybe one way to address small scale, insignificant in isolation but potentially damaging additive cumulative effects. Another way to address cumulative effects may be to introduce another step into the effects equation, covering the likely prevalence or recurrence of the effect - does the effect come up often, or is a rare or unusual effect? So should the equation be:

Persistence of effect * magnitude of effect * extent of the effect * probability of the effect * likely recurrence of the effect * consequence to receiving environment * possible mitigation (reduction) * plan weighting.

Effects and Urban Design

The Goal

The following is my first tentative start (and likely to be a heroic failure of an attempt) at developing a framework around effects rating under the RMA, with reference to urban design outcomes.

I’m giving this a go as there is so much variation as to describing effects in RMA processes, let alone what is an urban design effect.

Identifying effects, their scale and consequences is at the heart of RMA processes. Whether an activity causes a big or little effect is very important. The RMA is often about future effects, which further complicates things.

I will start with the basics and build up to the main issue – what an urban design effect is and how it might be rated.  What is an urban design effect is itself a big task. Is urban design normative (how the world should be) or is it positive (this is, just the way it is?). Is urban design evidence-based or is it just a bunch of nice ideas? There are many sets of urban design principles and lots of overlap with other RMA effects (like urban amenity, landscape, transport, ecology). There is also the confusion between urban design being focused on positive things to include rather than things to ‘avoid’ or ‘mitigate’. Urban design also has a big element of human behaviour to it, well at least I think it does, which complicates cause and effect.

So rather than get lost in what is an urban design effect, I will begin with  how effects should or could be rated. Then onto urban design. The two issues – what is an urban effect and how it should be rated – are connected and not easily subdivided, but you have to start somewhere.

Examples of effects ratings

Before getting into the detail of a possible rating system, it is worthwhile looking at some examples of effects ratings.  First up is the following scale that the Quality Plan website provides:

• Nil Effects:  No effects at all.
• Less than Minor Adverse Effects: Adverse effects that are discernible day-to-day effects, but too small to adversely affect other persons.
• Minor Adverse Effects: Adverse effects that are noticeable but will not cause any significant adverse impacts.
• More than Minor Adverse Effects: Adverse effects that are noticeable that may cause an adverse impact but could be potentially mitigated or remedied.
• Significant Adverse Effects that could be remedied or mitigated. An effect that is noticeable and will have a serious adverse impact on the environment but could potentially be mitigated or remedied.
• Unacceptable Adverse Effects:  Extensive adverse effects that cannot be avoided, remedied or mitigated.

There are six levels of effects, from nil effect to unacceptable effects, which gives a range. This is not a bad list, but it does tend to mix up a number of things:

• There is reference to effects that could be mitigated.  Just saying that they might be able to be mitigated doesn’t really help. Most effects can be mitigated to one extent or another. The real question is by how much and by what means. 
• Some effects are described by the opposite – a minor effect is not a significant effect, for example. Not much help.
• There are three types of effects hovering around the ‘minor’ threshold: less than minor; minor; more than minor. But then we skip to ‘significant’.  
• At what point do you transition from ‘more than minor’ to ‘significant’? Is there room for moderate effects (or are they ‘more than minor’, but not ‘significant’)? 
• The last effect – unacceptable effect - begs the question of unacceptable to whom?  
• There is a mix between people and the environment. A less than minor effect is an effect that doesn’t affect another person? But what if the effect is an effect on the environment, not people? 

It is not surprising that there is so much confusion as to how to describe effects as the RMA and related plans use the term 'effects' in so many different ways.

What does the RMA say about effects? 

The most common references in the RMA are to ‘minor’ effects and ‘significant’ effects, for example:

Assessment of environmental effects – schedule 6:

• an assessment of the actual or potential effect on the environment of the activity:
• if it is likely that the activity will result in any significant adverse effect on the environment, a description of any possible alternative locations or methods for undertaking the activity.

Sec 95 -notification:

• a person is an affected person if the consent authority decides that the activity’s adverse effects on the person are minor or more than minor (but are not less than minor).
• activity will have or is likely to have adverse effects on the environment that are more than minor.

Section 104 Assessment of consents:

• any actual and potential effects on the environment of allowing the activity

Section 104D non complying activities;

• the adverse effects of the activity on the environment will be minor

There are other references. Section 142 relates to Ministerial Call In. One factor can be whether irreversible changes to an environment are being contemplated.

As others have noted, there is a distinction to be drawn from the above between threshold tests and evaluation inputs. The thresholds generally relate to process tests: ‘if that type of effect is likely to occur, then this or that process is to be followed’. The thresholds determine which process route you head down, such as for notification and non complying activities. But they don’t tell you how to make the overall assessment.

So from a procedural or threshold test point of view, any rating system needs to be able to identify what is:
• Less than minor,
• Minor
• More than minor
• Significant
In terms of
• people and/or the
• environment,
to help wade through the procedural issues.

But it doesn’t stop there, as once you are into the section 104 process of assessing effects of a resource consent then it is helpful to have a more graduated set of effects than just minor or significant. Section 104 just refers to effects, as does schedule 6, and Part 2.

Once into evaluation, a graduated effects rating becomes more important and useful. Of course saying that an effect is only minor or no more than minor helps in that evaluation as there is probably no need to assess the effect in any more detail.  But saying an effect is more than minor is not helpful. A consentable activity can have effects that are more than minor. It all depends.

Here is another example of effects rating, this time from landscape assessment:

• EXTREME Total loss of the existing character, distinctive features or quality of the landscape resulting in a complete change to the landscape or outlook
•  VERY HIGH Major change to the existing character, distinctive features or quality of the landscape or a significant reduction in the perceived amenity of the outlook 
• HIGH Noticeable change to the existing character or distinctive features of the landscape or reduction in the perceived amenity or the addition of new but uncharacteristic features and elements 
• MODERATE Partial change to the existing character or distinctive features of the landscape and a small reduction in the perceived amenity 
• LOW A slight loss to the existing character, features or landscape quality 
• VERY LOW The proposed development is barely discernible with little change to the existing character, features or landscape quality 
• NEGLIGIBLE The proposed development is barely discernible or there are no changes to the existing character, features or landscape quality

This list has a more reasonable graduation of effects ratings, from extreme to very low. There are three effects above the moderate effect and three below. This feels logical, although you might say that it is introducing a bit of a trap in that it depends upon what is “moderate”.  I think this is called anchoring – you establish some sort of artificial reference point and everything above or below this point is good or bad, depending upon your perspective. Having said that, the words used help a bit – slight loss versus a major change, for example.

But how useful is the above list in working out what is more or less than minor, what is significant in terms of the threshold / procedural tests?

I guess you could try the following:

Rating	Extent of ‘Minorism’	Extent of Significance
Extreme	More than minor	Significant
Very high	More than minor	Significant
High	More than minor	Significant
Moderate	More than minor	?????
Low	More than minor
Very Low	Minor
Negligible	Less than minor

Is a low effect a more than minor effect? Minor is supposed to mean  “it is not likely to matter if that effect occurs”.

Is a ‘moderate’ effect a significant effect?  Most people will say that a high effect is an effect that is more than minor and significant.  But a moderate effect – is that more than minor, but not significant?

Setting aside the threshold test issues, perhaps more importantly for the evaluative functions of the RMA, the rating leaves some questions. The rating is based on the extent of loss or change from the current environment, you might say this is the magnitude of the change. That may be appropriate for some resources (like landscapes), but it tends to emphasis the loss rather than the gain.

And what about the extent of the change, is it to just a small area or a big area?

I should imagine that in getting to a rating, then things like the ascribed value of the landscape, the extent of change and the magnitude of change are all important.

In a ‘dynamic’ urban environment, the receiving environment will always be changing. How much change is reasonable to take into account? The RMA process allows for (yet to be developed) permitted activities and unimplemented resource consents to be considered to be part of the environment. But is this too narrow?

Does the rating scale also need to work for positive effects, as well as negative effects? There seems to be a move towards more of a balancing of negatives and positives. If the scale is to work for positives, can you have an extreme positive effect?

Having said all that, a rating which goes from negligible to extreme is probably a better scale for effects assessment under section 104 than trying to conjure up a rating scale that is driven by section 104D or notification tests. However any rating system would need to show the links to those thresholds.

What is an effect?

Time to look at the RMA and its definition of “effect” and whether that helps with how to rate effects.

The following is the definition in the RMA. As we all know, it is a wide definition.

In this Act, unless the context otherwise requires, the term effect includes:
• any positive or adverse effect; and
• any temporary or permanent effect; and
• any past, present, or future effect; and
• any cumulative effect which arises over time or in combination with other effects regardless of            the scale, intensity, duration, or frequency of the effect, and also includes—
• any potential effect of high probability; and
• any potential effect of low probability which has a high potential impact.

Interestingly, I never really thought what the words ‘unless the context otherwise requires’ at the start of the definition mean. Are those words saying that there could be other types of effects that are not listed?

The different components of the RMA definition of effects can be expressed in a yin/yang kind of way, I guess:

• Positive or negative
• Temporary or permanent
• Present or future
• Cumulative or singular
• Actual or potential.

The last binary choice – actual or potential – is not directly stated as such in the definition. The term is used in various sections, such as 104. It is a useful term though, given that the last two types of effects listed in the definition are ‘potential’ type effects, namely:

• High probability
• Low probability but high consequence.

These effects relate to the same quality – namely the probability that an effect may occur. Some effects are certain, some effects may be highly likely, or they may be unlikely.  Of course being unlikely may still be a big problem if the consequences are bad.

I think the probability bit of any effects assessment needs to be its own step and urban design effects assessment probably needs a stronger element of probability to it (think of the dose-response relationship in medicine: give people this amount of drug and x%  recover. Change the environment in this way with that design and 70% of people are likely to be worse off, or something like that).

Perhaps a different way of saying the same thing is the degree of certainty that the effect will eventuate. In many cases, there may be 100% certainty that the effect will occur. In other cases it may 80% or 20%.

Are urban design effects ‘future’ effects, or are they always ‘present effects’? Bit hard to know what a future effect might be. Is a future effect an effect that is delayed in its operation – does the effect only manifest itself after 5 years - a bit like climate change, carbon emitted today means warmer temperatures and seal level rises in 50 years time? A blank wall to the street is going to slowly erode the sense of amenity when walking along the street which may only become apparent in two or three years time. Alternatively, or in addition, is a future effect a lost opportunity?

If we then say that urban design effects are mostly about permanent effects that are present or future effects, then we could summarise the task as:

Urban design effect = a permanent, present or future effect to an urban environment multiplied by the probability of that effect occurring. 

But this feels a bit truncated. Does the RMA definition leave somethings out? Is the definition in the RMA up to the job, given it was developed 20 years ago and may not have given much thought to urban areas?

Three things that come to mind in an urban context are:
• Systemic effects
• Longevity of effects
• Reversibility of effect.

Taking each of these in turn.

Systemic effects:

Cities are systems. Change one thing and something else can change somewhere else. In medical terms systemic effects have been described as:

Consequence that is either of a generalized nature or that occurs at a site distant from the point of entry of a substance. 

Systemic effects are a bit like cumulative effects. They exist, but it is jolly hard to pin them down.  Conceptually, consideration of the magnitude and extent of an effect could take into account systemic effects. Perhaps there needs to be some explicit assessment of ‘indirect or second order effects’ arising from an activity.

Longevity of effect and reversibility are more to do with the persistence of an effect. Do some effects have a half life – does their impact decay over time to something more benign? In a city that is constantly changing, do some effects just wear off after or a while or just blend into the background?

Reversibility is also an interesting issue: urbanisation is generally irreversible. Building a tall building is irreversible, but not completely so. Changing uses tends to be reversible at some point.
While effects can be temporary or permanent, there is not much of a graduation between these two ends of the spectrum, when perhaps there should be in an urban context.

Possible effects rating equation  

What I'm thinking about is whether getting to a rating of an urban design effect (setting aside what the effect is) requires at least 7 steps, namely:

Rating equals: Persistence of effect * magnitude of effect * extent of the effect * probability of the effect * consequence to receiving environment * possible mitigation (reduction) * plan weighting.

This is my working hypothesis:
1. Persistence of effect refers to the longevity of an effect, is it permanent, or will it reduce             overtime?
2. Magnitude of effect refers to whether, to put it simply, there is a big or little effect?
3. The extent of effect refers to how much of a receiving environment is affected (large area or small area?)
4. The probability of the effect recognises that there is no certainty around, persistence, magnitude and extent of effects.
5. The existing and future receiving environment is recognition that things can change (as allowed for by the plan), as well as the sensitivity of the environment to change. This brings in consequences.
6. Possible mitigation refers to the extent to which the magnitude, extent, probability or consequences of the effect could be reduced
7. Plan weighting refers to the importance or otherwise that the plan ascribes to the effect. The plan may allow for the effect, say that significant effects have to be avoided, or effects mitigated. There is a wide range.

You may debate whether the last two steps are part of the rating. ‘Plan weighting’ is a matter for the  planner to work out. But if the plan provisions are ignored in the urban design analysis, then effects may be over or under rated.

You can also debate whether mitigation should be in there. Should effects rating be before or after mitigation? However going through a long process of rating effects, but then saying ‘while this is a nasty effect, it can be mitigated” is a bit unhelpful. By putting mitigation into the equation, it should be made more explicit as to how much of the effect can be mitigated.