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The Consequences of Demographic Change for Municipal Infrastructure
Matthias Koziol
The Consequences of Demographic Change for Municipal Infrastructure
1. The Phenomenon of Shrinkage - New Starting Conditions for Municipal Infrastructures
2. Qualitative Effects of Shrinkage and Redevelopment on Systems and Networks
3. Quantitative Effects on the Efficiency of Networks - Critical Threshold Values for Utilization
3.1 Drinking Water Supply
3.2 Sewage Disposal
3.3 District Heating
3.4 Transport
4. Ecological Repercussions
5. Influence of Urban Redevelopment Plans on the Technical Infrastructure
6. Economic Repercussions of Demographic Change on the Technical Infrastructure - Costs and Price Development
7. Prospects
8. Conclusions
Abstract:
The consequences of demographic change are particularly evident in the superimposition of several processes in the new federal states. For technical infrastructure systems this development has already begun to hamper efficient operation and generate follow-up costs. One of the main determinants of these costs is the urban redevelopment strategy pursued. In the years to come, housing service and maintenance costs are likely to rise in shrinking communities. To avoid or at least limit higher ancillary costs and the consequent worsening of locational conditions in the municipalities affected, low-cost urban renewal strategies, i.e., economically sustainable urban redevelopment, need to placed high on the agenda. An examination of how urban redevelopment affects the technical infrastructure provides valuable insights which can be transferred to other aspects of urban renewal.
1. The Phenomenon of Shrinkage - New Starting Conditions for Municipal Infrastructures
Urban shrinkage, provoked by demographic change and migratory movements, poses complex problems for housing companies, urban planners, and politicians. But the operators of technical infrastructure systems also face a completely new situation, objectively and subjectively. Having to cope with dwindling consumption, a decline in customer or tenant numbers is not only felt to be a negative development but also creates completely new framework conditions in planning and operating durable infrastructures.
For the technical infrastructure, which is the focus of this article, shrinkage processes play a role on several levels. Declining consumption and smaller service areas are the most striking characteristics. Developments are determined by:
- sinking specific water, heating, and electricity consumption owing to changes in consumer behaviour or technical improvements in equipment or control mechanisms;
- lower consumption owing to small-scale migratory movements (simultaneous service area deconcentration and expansion);
- declining consumption owing to extensive migratory movements (outmigration accompanied by service area deconcentration);
- reduced consumption due to demographic developments (population decline);
- falling commercial and industrial demand for network-related infrastructures (plant closures, improved equipment);
- network reduction through building demolition.
In shrinking cities, the effectiveness of these factors appears to be a long-term perspective because of the negative trends in demographic development. Only massive inmigration or a substantial change in reproductive behaviour, i.e., a significant increase in the fertility rate, can reverse this trend. This leads to serious, long-term changes in urban structures. Urban redevelopment, provoked on the face of it by housing industry considerations and pursued with spatial and programmatic objectives differing from municipality to municipality and thus with differing consequences for network infrastructures and urban technology, can be regarded as a reaction to this situation.
The process of urban shrinkage and redevelopment confronts the utility sector, particularly in the new federal states, with a difficult challenge. The fall in specific drinking water consumption since 1990, the drastic decline in industrial water consumption and dwindling population are already threatening many technical infrastructure networks with high levels of idle capacity and serious consequences for efficient operation and cost effectiveness.
Even allowing for shrinkage since 1990 due to higher prices and charges and rehabilitated mechanical services, drinking water consumption and household sewage volumes have fallen by between 25 per cent and 30 per cent. Over the same period, district heat sales fell by similar amounts due to improved insulation and control engineering.
In residential areas with vacancy rates of, for example, 30 per cent, drinking water and sewerage network utilization loads have already fallen by more than 50 per cent compared with design loads. In many places commercial and industrial water consumption has also fallen drastically. For example, drinking water consumption in Schwedt/Oder including the areas served in surrounding Uckermark County fell from about nine million cubic meters in 1990 to some three million in 2002, despite an increase in the number of households connected and substantial expansion of the network.
2. Qualitative Effects of Shrinkage and Redevelopment on Systems and Networks
Network utilization levels have a fundamental impact on the efficiency of operation and economic viability. In the past, in effect since the network infrastructure was built, the main problem was how to eliminate overload by expansion or appropriate operation; the main concern now is the effect of underutilization and how to cope with it. In some municipal services, underutilization has reached such dimensions that the effects have become fully manifest. For example, the costs of odour control at the Frankfurt/Oder water utility (FWA) sextupled within ten years from about € 10,000 to some € 60,000 per year. Similarly, the amounts of flush water used to maintain the operation of the sewerage network sextupled between 1999 and 2001 from 1,920 cubic meters to 11,852 cubic meters.
In general terms, the problems that shrinkage poses for network-related technical infrastructure can be summed up as follows.
- In sewage and waste water disposal, lower flow rates lead to sediment deposition in oversized sewers, especially in low gradient sections. This makes it necessary to flush sewers frequently. Anaerobic transformation processes due to deposits and long sewage retention times cause odour problems (e.g., in inverted siphons, storage basins, pumping stations, transfer points from pressure mains to gravity mains, etc. Degradation processes resulting from sedimentation furthers the corrosion of pipe material (e.g., pumping station storage basins, shafts). Decreasing amounts of effluent reduce the efficiency of existing, increasingly oversized sewage treatment plants and impair operation through surges of dirt after rain and rising proportions of extraneous water.
- In the drinking water network, lower consumption leads to longer water retention times and consequently to a greater risk of bacterial aftergrowth. This danger is particularly great during the temporary fall in consumption during the summer months (school holidays, etc.) and in the case of combined fire-fighting water and public drinking water supply, which requires large pipe diameters.
- In district heat networks, vacant housing leads to a (relative) rise in heat transport losses, to generation plant overcapacities, and hence to a general reduction in system efficiency and profitability. Moreover, lower heat consumption can cause the collapse of steam networks. The only solution is conversion to high temperature water networks. Simple retrofitting is excluded by differences in pipe diameters (flow line/condensate return) and statical problems. Inadequate capacity utilization of total energy units can necessitate the disconnection of individual modules. In extreme cases this can lead to operation with peak boilers alone.
- Both positive and negative effects are likely with regard to transport. On the one hand, vacant housing and much greater living space per resident eases the burden on existing parking space. On the other hand, rail-bound systems (tramways) have to accept much lower utilization rates and cost-effectiveness when vacancy rates in the service area are high.
3. Quantitative Effects on the Efficiency of Networks - Critical Threshold Values for Utilization
The functional importance of residential vacancies, demolition and downsizing differs for the various media and constellations of network public utility services, and especially for the rail-bound transport sector (tramways, etc.). Examples of effects and interdependencies in certain infrastructural fields (drinking water supply, sewage disposal, district heating, transport) are to be looked at in outline. Effects apparent without demographic change are treated overall as boundary conditions. The following examination of public utility services applies mutatis mutandis for telecommunications and power supply systems and networks. But in comparison to the media mentioned above, the functional problems in these areas are substantial less serious.
3.1 Drinking Water Supply
A strong reduction in flow rates can cause considerable problems for the functioning of water supply networks. Higher housing vacancy rates can have a particularly serious impact in areas where the fire fighting water supply is coupled with the drinking water network. The large line diameter (large pipe volume) means very low flow rates. The result is stagnation zones, sedimentation areas (precipitation), as well as long drinking water retention times in lines. This tends to increase the risk of bacterial aftergrowth.
A direct comparison of a particular demand situation at the time of planning and original dimensioning of the drinking water system and capacity utilization in 2003 shows clearly that the fall in private household water consumption (consumption density) is due primarily to the reduction of average occupancy density from three to under two persons per residential unit and to the fall in specific water consumption from between 200 and 220 litres per resident and day (design value) to between 80 and 100 litres per resident and day. These two factors alone reduce water demand and sewage volume by some 70 per cent under design capacity. Furthermore, the effects of residential vacancies add up, resulting in a well over 70 per cent drop in consumption in many high vacancy areas.
The consequent risk of bacterial aftergrowth in drinking water supply lines depends strongly on temperatures. The danger is particular great in newly laid networks still without throughflow (e.g. in newly developed, unoccupied industrial estates) and in sections of line with high ambient temperatures (e.g., basement lines), although an overall link between vacancies/demolition and changes in drinking water quality cannot be shown.
3.2 Sewage Disposal
Depending on the sewage disposal system (separate sewerage system, combined sewer system), declining water consumption can in many places lead to a strong reduction in sewage volumes, falling below the required minimum flow rates. Failure to attain the minimum flow rate leads to sedimentation and, where flow times exceed ten hours and oxygen content is low, to the formation of H2S, HS-, S². When sulphate reduction sets in, hydrogen sulphide forms, and in the presence of condensed water vapour biogenic sulphuric acid forms at cold places in the collector sewer, corroding concrete elements.
In simple terms, it can be said that dispersed residential vacancies or more than 50 per cent downsizing prevents the necessary flow rate from being attained when sewage discharge pipes are laid at a minimum gradient - which is often the case in developed areas without major differences in height. This rule of thumb takes into account the considerable changes in specific water consumption after 1989 and approximately ten per cent extraneous water. To some extent, sewers were badly laid in the past at a gradient below the required minimum. Where this is the case the reduction in consumption has an even stronger impact.
3.3 District Heating
The technical efficiency of district heating systems can generally be maintained with the largely existing high temperature water networks regardless of housing vacancy rates. More problematic is the position with steam networks, where condensation problems can arise if a critical demand level is not reached, leading to the breakdown of the networks. The only solution is (expensive) conversion to a high temperature water network.
In any case, the continued reduction in supply density can be expected to bring higher operating costs, e.g., through higher specific heat losses during transport (mains losses). When lines are too large, the system tends to become less efficient and more difficult to control. If district heating pipelines run through basements, sections of pipeline and house substations may have to be extended or replaced (new construction) to supply the remaining buildings in the area.
Within a certain range, the following rule of thumb can apply: if heat consumption in the entire supply area falls by more than 50 per cent for a constant network in comparison to design specifications, heating supply alternatives may prove more economical in terms of primary energy use, e.g., decentralised heat supply on the basis of natural gas. Depending on the rehabilitation status of the building concerned (thermal insulation), this threshold is reached at roughly 20 per cent to 40 per cent in the case of scattered vacancies or downsizing. A precise estimate of the resulting CO2 emissions, however, depends on a number of parameters and can be made only for concrete cases.
3.4 Transport
In the transport field, lower population density due to demographic decline has eased the parking problem, which had become considerable after the demise of the GDR. Additional parking space is no longer needed in many residential areas with vacant housing, and the situation is manifestly easier.
More problematic is the impact on public transport, particularly rail-bound systems like tramways. Especially in high-density prefabricated housing areas, vacancies have reduced system utilization, particularly since the substantial shift in modal split towards private motorised transport since unification. Local authorities can find themselves forced to increase tramway operation and maintenance grants or even to shut down systems.
In general, municipalities will have to pay more for the upkeep of road systems, since the cost of repairs, cleansing, and winter maintenance, for example, can no longer be passed on to non-existent frontagers when housing has been demolished or scaled down. In individual cases, networks have to be adjusted, i.e., streets and pathways downsized.
4. Ecological Repercussions
For the sake of completeness, the ecological repercussions of shrinkage processes should not be forgotten. Although falling consumption can generally be expected to ease burdens on the environment, i.e., to have a positive impact on resource consumption, in practice it can have negative ecological repercussions, e.g., by hampering the operation of network-related systems.
Reduced efficiency in heat generation, e.g., through cogeneration, can endanger the ecological advantages of system solutions (emission balance). Greater corrosion in sewers/shafts can have a nefarious effect on groundwater protection. Anaerobic transformation processes in pipe lines lead to odour nuisances. The need for more frequent pipe line cleansing thwarts efforts to save water. Longer retention times in drinking water networks may necessitate safety chlorination and affect water quality.
Among the factors that determine the scale of consequences are the actual extent of shrinkage processes and the type of adjustment measures adopted. Cost-intensive constructional adaptation of pipe line systems and installations may have less serious long-term ecological repercussions than primarily operational measures, since functionalities can be upheld. But it is unlikely that investment in constructional adaptation for shrinking urban areas can be maintained in the long run.
5. Influence of Urban Redevelopment Plans on the Technical Infrastructure
For the moment, the utility sector is reacting to increasing housing vacancies primarily with operational measures, e.g., flushing the sewerage network to improve flow properties and avoid odour nuisance. As a rule, however, this increases operating costs and ultimately leads to higher prices and charges which accelerate the fall in consumption. It is therefore not a long-term solution.
More important, indeed decisive in determining the long-term impact of demographic change are the underlying urban redevelopment constellations. They affect the technical infrastructure in many ways. Three deserve particular attention.
Storey-wise downsizing does not change the structure or length of networks. If the underutilization of public utility networks does not reach critical functional limits, "only" cost increases from appropriating fixed costs to a smaller number of consumers are to be expected. If, however, the critical functional limits are not reached, even in the medium and long term, considerably higher operational costs will be incurred, for example for line flushing and/or investment to adapt plant and pipeline dimensions. For sewerage lines, the critical threshold can be roughly 50 per cent vacancies or dispersed demolition/downscaling (where lines are laid at minimum gradient). The stabilisation of settlement density well above this figure is therefore desirable. In the long term, however, storey-wise downscaling entails too high specific replacement investment for network redevelopment, since the entire system has to be renewed for fewer customers.
Isolated or segmental demolition, i.e., the removal of single buildings from the development complex, has an impact on the distribution system comparable to that of storey demolition. Connections for several buildings via basement routing are an exception. In such cases partial demolition can require additional investment in the urban redevelopment phase to close gaps or relocate lines and installations.
Through the extensive, systematic demolition of buildings, for technical reasons best carried out from the ends of distribution systems, the extension or relocation of lines and installations can generally be avoided. Hence, it causes the least technical problems, since demolition more or less reduces the network in the reverse direction of its construction. In this case, shutting down parts of the system is generally also no problem. In the long term, this demolition strategy reduces the improved settlement area, thus shortening networks and cutting replacement costs in the event of network renewal.
If an urban redevelopment area is on the periphery of a supply area, i.e., there are no further settlement areas or individual properties to be supplied "beyond," part of the mains system can be shut down or downscaled in the course of demolition. If the urban renewal area is located between two or more settlement or supply areas, the remaining "common carriage sections" require particular attention.
If it is assumed that the shrinkage processes caused by demographic change will be a durable phenomenon, extensive demolition - where possible from network ends - will in the long run be the only way to ease the specific technical infrastructure cost burden to be borne by users.
6. Economic Repercussions of Demographic Change on the Technical Infrastructure - Costs and Price Development
In considering follow-up costs, a distinction must be drawn between indirect costs incurred because of changed consumer habits and lower settlement density and direct costs incurred through higher operating costs, redevelopment, and the adaptation or downsizing of pipeline networks.
The fall in consumption after 1990 alone can raise costs for consumers considerably - on condition that 100 per cent are apportioned in keeping with the cost-recovery principle. In the event of dispersed downsizing, i.e., where the existing settlement area and the existing network structure are largely retained, substantially higher costs are to be expected in the long term (cf. figure 1).
The urban redevelopment plans analysed so far entail the following "rough reference figures" for adapting and downsizing network infrastructures for individual media in euros per demolished square metre of floor area (cf. figure 2).
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Figure 1: Changes in total costs for network-related media with rapid population decline dispersed housing demolition in euros per resident and year 
Source: own presentation. |
Depending on the urban redevelopment strategy adopted and provided that redundant lines are demolished, direct costs averaging (an estimated) € 800 to € 1,500 are incurred per dwelling unit and € 15 to € 25 per square metre of demolished floor space for the downsizing of pipelines, diversion or relocation (e.g., for basement routing sections). A key cost factor can be the downscaling of collectors. The costs mentioned above take no account of measures affecting central installations outside the urban redevelopment areas, like the adaptation of pumping stations, distribution stations, main collectors, sewage treatment plants, cogeneration plants, etc, or of their net book value.
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Figure 2: Cost areas for downsizing and adaptation and net book value 
Source: own presentation. |
In the case of dispersed demolition, direct downsizing costs are reduced, since fewer lines and installations have to be removed. But the indirect costs incurred increase owing to the apportionment of fixed costs for the larger remaining network among a smaller number of consumers in direct proportion to population decline.
Left out of account are the follow-up costs in both cases for central infrastructure facilities, which have yet to be sufficiently examined. If costs cannot be passed on to the consumer, the suppliers will have to accept losses in revenue.
Even if these costs constitute (only) an initial cost framework, which may be adjusted downwards with increasing experience in urban redevelopment, the aim is save expense by obviating adaptation and renewal measures, i.e., by adopting an appropriate redevelopment strategy. There is great potential in systematic downscaling from the ends of networks, which may permit lines to be left in place provided that structural safety is ensured and the legal position is clarified.
7. Prospects
It is of crucial importance for future development to note that rising housing vacancies and falling occupancy density imply a marked increase in specific line length per resident in the current supply areas. This is shown in figure 3.
Taking the example of the East Uckermark Joint Water Supply and Sewage Treatment Authority (Schwedt/Oder and surrounding areas with a total of some 70,000 residents), the forecast offers two development scenarios.
a) Development ceases in the less densely settled area (lower curve). b) Moderate expansion of extensive settlement continues, connected to the existing central water and sewage systems (upper curve). The official population projection (Brandenburg State Environmental Office) also provided data. Note: water supply figures much higher than the values for specific sewer lengths are to be explained by, among other things, a higher proportion of supra-local lines.
Owing to the "deconcentration" of settlement areas, demographic change therefore considerably increases tied-up capital investment per resident, ultimately diminishing the cost-efficiency of existing systems. In other words, technical infrastructure charges and prices will have to rise if the cost-recovery principle is to apply.
In comparison with less strongly shrinking, stable, or growing municipalities or regions, locational conditions deteriorate.
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Figure 3: Development of specific line lengths per resident for water supply and sewerage systems in the East Uckerbark Joint Water Supply and Sewage Treatment Authority in comparison with median specific line lengths in Brandenburg 
Sources: calculations Matthias Koziol and Institut für Abwasserwirtschaft Halbach. |
8. Conclusions
The phenomenon of shrinking cities confronts the planners and operators of utility technical infrastructures in the new federal states with a completely new situation. As specific consumption drops and population declines, many technical infrastructure networks will be used far below capacity and malfunctions will begin to increase.
The assumed economic superiority of central systems, which used to be accepted for all metropolitan areas, will be relativised. The enormous basic investment in utility lines for drinking water supply, sewage disposal, electricity, and district heating are reflected in long-term effective fixed costs, the key component of charges and prices (50 per cent to 80 per cent) for provision of these services. They thus contribute considerably to housing service and maintenance costs, which, in the case of unrehabilitated panel-construction housing, is often little less than the basic rent.
Passing on the full direct and indirect costs of infrastructure adaptation to the consumer is often impossible for political and legal reasons. Depending on the urban redevelopment/downsizing strategy adopted, high direct costs are incurred in scaling down, diverting, and relocating service lines (e.g., in areas with basement routing), for adapting pumping stations and distribution stations etc., while indirect costs arise from apportioning existing fixed costs among a smaller number of consumers.
The following recommendations can be made for adapting technical infrastructures in ongoing urban redevelopment: (1)
- Utility sector concerns should be taken into account at an early stage in drawing up and updating municipal redevelopment plans.
- Urban redevelopment planning must be based on serious development prospects and not on best case assumptions.
- From the technical infrastructure point of view, extensive downsizing has priority over dispersed downsizing; if possible it should be carried out from the ends of networks (cost-effective adjustment by concentrating points of main effort). Partial demolition should be undertaken only where population density falls by up to 30 per cent.
- Where possible, urban development restructuring should use existing networks. Clear decisions for or against substitute uses of demolition areas should be made at an early stage.
- Where possible, no extensive demolition should be undertaken on the remaining main network axes.
- In the environs of less utilized sections of networks or in the vicinity of potential demolition areas, no further constructional development should take place outwards.
- Where a long-term advantage is to be attained, distributed solutions should be envisaged.
- The adaptability of networks should be taken into account and enhanced in the course of any remedial measures required.
- Planning should take account of developments and demand in the city-suburban complex.
- New service lines and facilities should kept within reasonable dimensions.
- Investment intensity should be optimised in keeping with the urban redevelopment strategy adopted.
Implementing these recommendations will not always prove possible in harmony with short-term housing industry and urban development requirements. Strategies and measures must therefore be carefully weighed up and urban redevelopment processes comprehensively coordinated and mediated. This is crucial for sustainable urban development under conditions of shrinkage.
Notes
(1) A comprehensive treatment of the links between the mechanisms of urban redevelopment and the technical infrastructure is to be found in a manual produced by the Institute for Urban Development and Housing Frankfurt/Oder (ISW) and the Department of Urban Technology at the BTU Cottbus. This publication offers ideas for conceptual work and material for discussion on sustainable urban redevelopment. The manual, entitled: "Anpassung der technischen Infrastuktur beim Stadtumbau" ("Adaptation of the technical infrastructure in urban redevelopment") can be obtained from the Institut für Stadtentwicklung und Wohnen des Landes Brandenburg (ISW) Müllroser Chaussee 48, 15236 Frankfurt/Oder. (back)
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