Backs to the Nala: Why India's Urban Streams Stay Drains Until Their Edges Turn Public

Small streams once organised Indian settlements. Today most nalas, odhas and rajakaluves carry stormwater and sewage behind compound walls, seen from rear windows and crossed without a glance. Plans treat them as drainage assets and riverfront schemes treat them as real estate; few ask how the city meets the water. Drawing on river-connectivity research, national guidance and state regulations, and on map measurements in Pune and Bengaluru, this article argues that a nala stops being a back-of-house drain only when its edge is designed as public realm, and proposes a five-part field diagnostic.

Sujeet S. Thakare
Urban Design & Planning

Every large Indian city is threaded by small streams that rarely appear in its self-image: the Nagzari and Ambil Odha in Pune, the rajakaluves that once linked Bengaluru's tanks, the nallahs running to Mumbai's Mithi. Most are a few metres wide, dry for half the year and violent for a few days of it. In everyday speech they are simply "the nala", a word that has slid from meaning a stream to meaning a drain.

The slide is usually blamed on pollution and engineering. This article argues that the more decisive failure is one of urban form. Small streams stay drains because the city has been allowed to build its backs to them. Plot boundaries run to the water, compound walls take the bank, rear outfalls discharge into the bed, and the street, where public life and public custody sit, stays one or two plots away. A channel that no one faces is a channel no one watches, reaches or defends.

The argument is organised around five questions that together make up a field diagnostic, BANKS-5: Bearing (do buildings face the water or turn away?), Access (can anyone reach the water and walk along it?), Natural buffer (is there a continuous planted strip at the bank?), Keeping room for water (does the section hold monsoon flow or only hurry it?) and Stewardship (who holds the edge and keeps it?). The sections that follow summarise the research and regulatory base, describe the map method and its limits, analyse each axis with original drawings of real Pune and Bengaluru reaches, discuss what transfers and what does not, and close with implications for practice.

What the research says

Ecologists have described the condition of urbanised streams for two decades. Walsh and colleagues' synthesis of the "urban stream syndrome" sets out its consistent symptoms, among them flashier flows, elevated nutrients and contaminants, altered channel form and reduced biological richness, and identifies hydraulically efficient drainage, which moves runoff from roofs and roads into channels as fast as possible, as a principal driver (Walsh et al., 2005). Their most relevant conclusion for designers is that the remedy is likely to lie at catchment scale, in how stormwater is held and dispersed, rather than in the channel alone.

Geomorphologists have since extended the idea of connectivity from water and sediment to people. Kondolf and Pinto (2017) distinguish longitudinal social connectivity (movement along a river), lateral connectivity (reaching and crossing it) and vertical connectivity (from walking on the bank to touching the water). Their historical reading suggests that straightening and walling channels tended to sever the lateral and vertical relationships that sustained everyday use. The framework scales down: a nala's lateral connectivity is simply whether a lane, a step or a doorway reaches it.

Indian evidence points the same way, with sharper stakes. A ten-city working paper by WRI India estimates that between 2000 and 2015 built-up area grew by about 47% within 20 km of city centres and by about 134% in the 20–50 km periphery, while blue cover fell by roughly 15%, and that some 44% of new development occupied areas of high groundwater-recharge potential (Goswami et al., 2023). For Bengaluru, Ramachandra et al. (2012) report a 632% increase in built-up area between 1973 and 2009 alongside a 79% decline in water-body area, and link recurrent flooding to encroached, narrowed and concretised drains and the loss of wetlands. The drain has been asked to do the work of the landscape it replaced.

Social research on access complicates any purely ecological fix. In interviews in Madurai and Ahmedabad, Dempsey et al. (2018) found that free, public and safe access to rivers had declined, with some respondents describing the Sabarmati riverfront as designed to keep people away from the water and objecting to charges for its spaces; the same scheme had involved large-scale resettlement of riverside households (Desai, 2012). In Bengaluru, Unnikrishnan and Nagendra (2015) compared lakes managed through public–private partnerships with publicly managed lakes and found that the latter supported a wider range of traditional livelihoods and cultural uses, concluding that privatised management may deepen inequities of access. Restoration, these studies suggest, can produce a water edge that is cleaner and less public at the same time.

Where restoration has created public edges, the gains appear to concentrate where people can get in. Kang and Cervero's (2009) hedonic analysis of Seoul's Cheonggyecheon found land-value premiums for non-residential parcels near the restored stream that were notably higher within walking distance of its entrance points than near the former freeway ramps. Yet a systematic review of stream daylighting finds the literature thin on built form and urban design, inclusive planning and Global South cases (Khirfan et al., 2020); the urban-design canon fills part of that gap. The principle that public fronts should face public space while private backs face each other is long established in perimeter-block theory (Bentley et al., 1985); Jacobs (1961) warned that single-use edges become "border vacuums"; and Gehl (2010) shows how soft, permeable ground-floor edges sustain staying activities. A nala lined by plot backs is a border vacuum by construction.

Indian guidance has begun to absorb these ideas. The national Urban River Management Plan framework defines a nala as a local natural stream that may carry water or wastewater, observes that the connection between citizens and rivers has weakened, and recommends a riparian buffer that is ideally continuous and 12–15 m wide, counting only buffers wider than 7.5 m in its indicators; it also notes that small parks, ghats and urban forests can be as effective as continuous promenades (National Mission for Clean Ganga & National Institute of Urban Affairs [NMCG & NIUA], 2020). Maharashtra's unified regulations require a 6 m margin from the edge of a notified nallah, of which a 3 m strip is to be available as a public cycle track kept outside compound walls, with development rights offered in return (Government of Maharashtra, 2020). In Bengaluru, the Supreme Court set aside the National Green Tribunal's wider general buffers and restored those of the city's 2015 master plan, which for drains run to 50, 25 and 15 m by drain order (Mantri Techzone v. Forward Foundation, 2019). Mathur and da Cunha's (2009) SOAK offers the design counter-argument to all of them: that monsoon cities should hold rain in gradients rather than train it between walls.

Method and sources

The analysis combines a review of peer-reviewed research, national guidance, state regulations and court records with original measurements on OpenStreetMap (OSM) data for two windows: old Pune around the Nagzari and Manik streams, and the K100 primary drain through Koramangala and Ejipura in Bengaluru. Each open channel was sampled every 4 m. From each bank a perpendicular ray of 22 m recorded whether it met a public street or path running roughly parallel to the channel before any building ("public edge"), a building first ("back turned"), or neither ("open or unmapped"). Public entries were counted as street crossings and street ends within 15 m of the channel. OSM building coverage is incomplete in both windows, so "open" overstates true open bank; figures are reported as mapped. Sections are indicative, not surveyed or hydraulically modelled.

Analysis

Bearing: the bank as the back of the plot

Figure 1 shows the result for Pune. Along the 1.45 km of the Nagzari open in the frame, a public street or path comes before the first building on only about 19% of bank length; on 27% a building comes first, and most of the remainder is open or unmapped ground behind plots. The Manik's open upstream reach performs only slightly better, at about 25% public edge. Downstream, the Manik disappears: it is mapped as culvert for roughly 1.7 km in the frame, against 1.1 km open, running under streets and plots before it reaches the river. The unrolled bank strips beneath the map make the rhythm visible. Public edges arrive in short bursts where a street happens to run alongside; between them, the bank belongs to whoever owns the plot.

Figure 1. Backs to the nala: bank-by-bank bearing of the Nagzari and Manik streams in old Pune, as mapped in OpenStreetMap, with the same banks unrolled below.
Source: Author's drawing and measurement based on OpenStreetMap data (© OpenStreetMap contributors, ODbL), 2026.

Figure 2 explains why. It draws the same 25 m between building lines twice. In the upper section the plots run to the drain: compound walls take the bank, a shed is built on the wall line, rear pipes discharge into a lined box, and street life faces the outer streets on either side. None of it needs a single bad actor. In the lower section the buildings are turned round. A 6 m margin of the kind Maharashtra's regulations already require holds a 3 m public track at the water and a front zone where an otla and shopfront can face the stream; the bank is planted rather than walled. The plot area lost is modest. What changes is the bearing of the building and the ownership of the edge.

Figure 2. Turn the building round: the same corridor with plots backing onto a lined drain (A) and fronting a planted bank with a public track (B).
Source: Author's indicative sections, 2026; margin after Government of Maharashtra (2020), Reg. 3.13.2.

Access: water you can see but not reach

A stream can be overlooked from rear windows and still be unreachable on foot. Figure 3 measures access on the K100 drain in Bengaluru, a primary rajakaluve that is the subject of the city's "Citizens' Waterway" project (Rajagopal, 2021). In the 1.1 km mapped open in the frame there are about eight public entries per kilometre, but only two are street crossings; the rest are street ends that stop at the edge. Buildings come first on about 47% of bank length. Combining the two measures, roughly 45% of the open channel has neither a public bank on either side nor an entry within 25 m. The comparison strips show a similar picture on the Nagzari (about 42%) and a better one on the Manik's open reach (about 29%), where crossings are more frequent.

Figure 3. Few ways to the water: public entries and unreachable reaches along the K100 rajakaluve, Bengaluru, compared with two Pune nalas at the same scale.
Source: Author's drawing and measurement based on OpenStreetMap data (© OpenStreetMap contributors, ODbL), 2026.

Entry frequency deserves to be a design criterion: value and use appear to gather where people can step in (Kang & Cervero, 2009), and a nala reached only every few hundred metres has lost most of its lateral connectivity, whatever its water quality (Kondolf & Pinto, 2017).

Buffer and room for water: the section decides

National guidance asks for a riparian buffer of 12–15 m, ideally unbroken (NMCG & NIUA, 2020). On the K100, a building stands within 12 m of the mapped centreline along about 35% of bank length, and for a primary drain several metres wide that leaves little room for any planted strip; in Pune the corresponding shares are lower, about 14–19%, though largely because many buildings near the water are not mapped.

Figure 4 sets two sections on a single datum. On the left, an 8 m lined box occupies the whole corridor between plots. On the right, a corridor of about 22 m is shaped as a two-stage channel: a low-flow channel that keeps water moving in the dry months, planted shelves that flood for a few days in a heavy monsoon, and sloped banks with trees and a path. The dashed water levels run across both halves. For a similar flow area, the lined box overtops into plinths and the street while the two-stage channel holds the same flood below the bank. Though indicative, the drawing makes Walsh et al.'s (2005) argument visible at street scale: the lined channel can only hurry water; the shaped corridor stores it, and its shelf is public ground for most of the year.

Figure 4. Room for the monsoon: a lined drain and a two-stage channel on one datum, with water levels running across both.
Source: Author's indicative section, 2026; not surveyed or hydraulically modelled.

Regulation is ambivalent here. Maharashtra's rules permit an owner to canalise a minor watercourse that lacks well-defined banks within the same land and then measure margins from the trained channel (Government of Maharashtra, 2020), which in effect allows the buffer to be shifted by first straightening the stream. Bengaluru's restored buffers are measured, in the judgment's account, from the middle of the drain (Mantri Techzone v. Forward Foundation, 2019), so a widened channel consumes its own buffer. Both details reward the lined box.

Stewardship: who holds the edge

The fifth question cannot be answered from a map. Bengaluru's K100 project set out to reframe the drain as an ecological corridor with pedestrian infrastructure, divided into roughly 1 km stretches, and acknowledged from the start that trunk sewers lie within or beside the drain and that illegal inlets feed it (Rajagopal, 2021). In April 2026, after a ₹179 crore programme had missed its January 2025 opening, residents along the route were reported to be complaining of stench and mosquitoes as sewage continued to enter the channel, while agencies disagreed over responsibility (Yacoob, 2026). A designed edge is necessary but not sufficient. Stewardship means a named custodian for the bank, sewage cut off upstream, free and unfenced entry, and a maintenance budget that outlasts the opening. The Bengaluru lake evidence suggests that the custodian matters as much as the design: public management appears to keep more kinds of user at the water (Unnikrishnan & Nagendra, 2015).

BANKS-5 as a field diagnostic

Figure 5 assembles the five questions on one reach of the Nagzari and Manik, drawn five times. Each plane isolates one axis, and each is paired with a measure that can be taken from open map data before a site visit and then corrected on foot: public-edge share for Bearing; entries per kilometre and unreachable share for Access; share of bank with a building inside the buffer for Natural buffer; culverted and lined share for Keeping room for water; and a short audit at each entry for Stewardship, asking who holds the key, whether there is a fence or a fee, and whether sewage still arrives. The readouts are prompts, not standards; their value lies in comparison under the same rules.

Figure 5. BANKS-5: five questions to ask of any urban nala edge, drawn on one reach of the Nagzari and Manik streams in old Pune.
Source: Author's diagram based on OpenStreetMap data (© OpenStreetMap contributors, ODbL), 2026.

Figure 6 shows what a passing score might look like on the most back-turned 300 m of the Nagzari. The first panel is a conjectural stream before the plots, with paths down to the water. The second is the reach as mapped today. The third is a proposal: a 12 m margin cleared of structures on each bank, a public track at the water, a few crossings and a planted bank. It uses only instruments already in Indian guidance and regulation, applied to the whole reach rather than plot by plot.

Figure 6. Stream, drain, edge: one reach of the Nagzari in three states, with matching indicative sections.
Source: Author's drawing based on OpenStreetMap data (© OpenStreetMap contributors, ODbL), 2026; stage 1 conjectural, stage 3 a proposal.

Discussion

Three limits deserve emphasis. First, the measurements depend on OSM: building coverage is partial, informal settlements along nalas are especially under-mapped, and private gates or informal steps are invisible, so the shares are indicative and comparable only under identical rules. Second, the regulatory instruments discussed are uneven. Maharashtra's 6 m margin and public strip apply only where a nallah has been notified and are not enforced where existing development makes them impossible (Government of Maharashtra, 2020), and Bengaluru's buffers have been contested in court. A diagnostic cannot substitute for that legal work, but it can show where it matters most.

Third, transfer from elsewhere is limited. Cheonggyecheon involved removing a freeway in a capital city with strong state capacity, and its land-value gains raise the question of who benefits (Kang & Cervero, 2009). Indian riverfront experience suggests that public edges created through clearance can reduce access for the poorest users even as they improve the look of the water (Dempsey et al., 2018; Desai, 2012). Any repair of nala edges has to deal with the households already living on them, and the BANKS-5 axes should be read as tests of a public edge, not as licence to clear one. Nor does the design argument replace the ecological one: a fronted, reachable bank above a sewer remains a sewer, and edge design must proceed with catchment-scale stormwater and sewage management (Walsh et al., 2005).

Conclusion / Implications for practice

This article has argued that the persistent failure of India's small streams is one of edge design: they are lined by plot backs, reached at long intervals, stripped of buffers, squeezed into lined boxes and kept by no one in particular. The measurements are modest and as mapped, but they point one way. On the reaches studied, between roughly a quarter and a half of open channel has no public bank and no nearby entry, and the public edge accounts for a quarter of bank length or less.

Several implications follow for practice. Development plans could map every nala reach with the five BANKS-5 measures and publish them alongside flood maps. Building permissions along notified nalas could require the public strip to be fronted, not merely left over, so that doors, otlas and windows face the track. Margins could be measured from a surveyed bank line rather than a trained channel or a centreline, so that canalisation does not consume the buffer. Drainage projects could be designed and costed as corridors with floodable shelves and entries at least every 100–150 m, an indicative spacing that the longest gaps measured here, about 240–270 m, plainly exceed. And every restored edge could carry a named public custodian and a maintenance budget from day one. None of these steps is exotic. Together they would begin to turn the nala from the back of the city to one of its fronts.

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Notes

Data. Figure-ground drawings and measurements use OpenStreetMap building, highway and waterway extracts (© OpenStreetMap contributors, ODbL), retrieved through an Overpass mirror and redrawn by the author, 2026. Measurement scripts and outputs are archived with the article's figure package. Sections and the framework diagram are indicative analytical drawings, not surveyed or hydraulically modelled designs.

Interests. No competing interests.

Preparation note. Regulatory provisions are summarised from the published texts cited and are not legal advice; readers should consult the current notified versions.

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