Localized flooding and autonomous adaptation in peri-urban Bangkok

Abstract

Peri-urban areas of mega-cities in lower-middle income countries face many environmental management challenges, including localized flooding caused by inefficient management and inadequate stormwater infrastructure. A case study analysis was conducted in Bangkok’s rapidly developing urban fringe, where residents have been experiencing localized flooding after normal rainfall. This paper explores the drivers of this flooding and its impacts for local communities, and explains how autonomous adaptation affects community stormwater drainage systems. The study found a mismatch between limited authority and transboundary problems of stormwater management, and calls for an integrated urban stormwater management approach. The findings imply the need to address autonomous adaptation as an integral part of adaptation measures at the broader scale of Thailand’s urban climate governance under the current threat of climate change.

I. Introduction

The extension of mega-cities beyond metropolitan boundaries in Asia has resulted in the emergence of mega-urban regions and extended metropolitan regions (EMRs), where patchworks of urban development spill haphazardly over surrounding agricultural fields on the city’s fringe.⁽¹⁾ EMRs represent a paradoxical situation: while they are the fastest-growing areas in Asia, with a significant share of GDP each year, these transition areas are poorly endowed in terms of environmental and socioeconomic services from the central government, due to overlapping jurisdictions and unclear management responsibilities.⁽²⁾ New roads and buildings from city core expansion interrupt and destroy existing hydrological networks and systems in areas once used for agriculture.⁽³⁾ Within new developments, existing waterways and natural drainage networks are incorporated into stormwater infrastructure systems or simply filled up during the construction grading process.⁽⁴⁾

Mega-cities in middle- and lower-income countries with rapid economic growth and urbanization are still struggling with basic problems of urban flooding due to inefficient drainage systems and improper solid waste management.⁽⁵⁾ There may be several reasons for urban flooding, including swollen rivers, coastal floods, pluvial and groundwater floods, and artificial system failures. Climatic conditions (e.g. extreme precipitation and flow) and anthropogenic activities (e.g. unplanned growth and development in floodplains) are considered the main drivers of urban flooding.⁽⁶⁾ In areas with poor drainage infrastructure and large areas of impervious surface, high surface runoff after normal rainfall can create localized flooding, considered a minor flood type whose impacts are confined to the affected communities.⁽⁷⁾ Localized flooding creates negative impacts for health, wellbeing and livelihoods, particularly for the peri-urban poor.⁽⁸⁾ Inefficient drainage and wastewater infrastructure systems result from inappropriate policies, poor institutional arrangements, outdated mandates, and lack of funding.⁽⁹⁾ Poor stormwater drainage management and flood control force private actors in different groups and on different scales to initiate their own flood adaptation and coping measures, which can sometimes lead to maladaptation.⁽¹⁰⁾

Several studies illustrate collective actions from autonomous adaptation in response to flooding within urban poor communities, which can reduce communities’ risk and vulnerability to climate change⁽¹¹⁾ and should not be seen as maladaptation.⁽¹²⁾ However, some studies argue that spontaneous adaptation at any scale without shared information among actors and an integrated approach may lead to maladaptation and create serious impacts for the most vulnerable groups.⁽¹³⁾ An intervention in one location or sector may increase vulnerability in another location or sector.⁽¹⁴⁾ Adaptation measures undertaken by affluent communities, such as new investment in drainage infrastructure, often aggravate flooding problems in other city areas.⁽¹⁵⁾ Thus negative externalities from autonomous adaptation in the peri-urban area deserve a closer look.

Focusing on one of the fastest-growing peri-urban areas in Bangkok, this paper explores how autonomous adaptation and coping measures in response to localized flooding can jeopardize a community’s public stormwater drainage management at local level and induce tension among stakeholders. The paper describes the drivers and impacts of localized flooding and explains how autonomous adaptation can become maladaptive.

II. The Concept of Autonomous Adaptation to Flood Risk

Autonomous adaptation refers to spontaneous acts driven by local experience to reduce risks from any specific environmental changes and enhance opportunities for wellbeing in the absence of official intervention and external support.⁽¹⁶⁾ In urban poor communities, flood adaptation and coping measures can reduce communities’ risk and vulnerability to a significant degree.⁽¹⁷⁾ However, autonomous adaptation can also cause an adverse impact when the decisions focus more on short-term outcomes than long-term threats, and this can exacerbate vulnerability to flooding.⁽¹⁸⁾ Empirical evidence indicates that autonomous adaptation undertaken independently without an inclusive decision-making process can jeopardize the most vulnerable groups.⁽¹⁹⁾

Three scales of agents involved in flood adaptation are: institutions, communities, and individual households.⁽²⁰⁾ At the institutional level, adaptation involves planning and water resource management.⁽²¹⁾ At the community and household levels, flood adaptation mainly involves modification of housing structures and the surrounding built environment to cope with floods. In terms of social measures, community members group together to share their efforts, knowledge and resources in negotiating with government agencies. Flood adaptation at community and household levels has its limitations because it can only generate minimally effective coping strategies, while the state’s central role can yield more inclusive and effective ones. It is necessary to opt for an integrative approach between the community and institutional levels.⁽²²⁾

Along with these three scales of agents, the private sector (industrial and residential business) significantly contributes to local flood adaptation. The private sector’s adaptation possesses similar characteristics to individual households that adapt for their own interest within a certain boundary. However, the private sector’s adaptation can increase risk to surrounding neighbours, especially marginalized groups.⁽²³⁾

In this paper, the concept of autonomous adaptation provides a framework for analysing physical and social responses to local flooding at the level of the individual household as well as the community, private sector, and institutions or public agencies in terms of their scale and activities. The concept also helps identify influential stakeholders in the study area’s stormwater drainage management.

III. Methodology

We selected a study area in the Pathum Thani province with a mix of farm and non-farm activities: the municipality of Lat-sawai (LSW). Within the LSW municipality, Village 5 was selected for a case study to observe localized flooding and local adaptation, and to capture the current state of stormwater drainage management at the local level of a typical peri-urban neighbourhood in Bangkok.

The study used mixed methods, with a combination of in-depth interviews, field observation and document review, to explore drivers and impacts of localized flooding and to explain how local communities adapt to it. The period covered was the rainy and flood season between May 2014 and January 2015. Purposive sampling⁽²⁴⁾ was used to select respondents who are either directly or indirectly in charge of local stormwater management (e.g. village headman, municipal engineer, irrigation officer, road engineer, provincial planners). The snowball method was used to select flood-affected households for interviews.

Two LSW municipality officers and seven civil servants at sub-regional offices (i.e. the South Rangsit Irrigation Office [SRIO] and Pathum Thani Rural Roads Office [PRRO]) were questioned to explain their responsibilities in local stormwater management and to describe how localized flooding occurred and affected the local stormwater drainage system. Eleven local residents were interviewed; they were asked to explain drivers and impacts of localized flooding, adaptation measures, and the municipality’s intervention in stormwater drainage management. The researchers also interviewed residents who had not encountered localized flooding to gain a background on LSW and past flooding incidents. Sketches and photographs from field observations were used as supporting tools during the in-depth interviews to communicate with local residents.

To triangulate the primary data collection, we reviewed documents and reports from government agencies, including Pathum Thani comprehensive planning reports, municipality and provincial development plans, and laws and regulations on the built environment (i.e. town planning acts, highway acts, land excavation and land filling acts, land allocation acts, and local ordinances).

Although this study is limited by its small sample size and single-case analysis, and cannot necessarily be generalized to other peri-urban areas with different socioeconomic and biophysical backgrounds, its scale did allow the researchers to establish a close association with the respondents and to capture the dynamic relationship between stormwater management and autonomous adaptation in a peri-urban area. Further comparative case analyses are recommended to supplement this study.

IV. Overview of the Study Area

a. Pathum Thani Province and LSW Municipality

Pathum Thani Province is one of the five provinces that comprise the Bangkok Metropolitan Region (BMR).⁽²⁵⁾ Pathum Thani is situated in the floodplain of central Thailand, directly to the north of Bangkok. The per capita income is US$ 9,823. Pathum Thani is classified as tropical savannah, and it has much less rainfall in winter than in summer. In 2011, the average temperature was 28.1º C, with average annual precipitation of 1,426 millimetres, highest in September.⁽²⁶⁾

Pathum Thani Province is bisected by the Chao Praya River, which runs north–south, dividing the province into the western and eastern parts. The eastern part is a large area of irrigated land, encompassing the four districts of Thanyaburi, Khlong Luang, Lum Luk Ka and Nong Suea. LSW is situated within the Lum Luk Ka district. The irrigation project, initiated in late 19th century by King Rama V, has resulted in a series of Khlong or canals within the area, where the main canals and lateral canals exist in a geometrical pattern.⁽²⁷⁾ In 1986, the unprecedented economic growth in Thailand transformed agricultural land use in Pathum Thani into industrial uses,⁽²⁸⁾ prompting the creation of factories and industrial estates, and accompanied by the emergence of new commercial and residential development in the existing agricultural fields.⁽²⁹⁾ Between 1952 and 2002, land use types in the province evolved from large plots of rice fields and orchards into a range of land uses including gated subdivisions, informal housing, apartments, townhouses, fishponds, wasteland, and some remaining rice fields and orchards.⁽³⁰⁾

The LSW municipality encompasses a total area of 33 square kilometres and is located within the southern area of Pathum Thani Province, a 50-minute drive from central Bangkok. In 2015, there were 58,207 people in 34,157 households residing in LSW, with a population density of 1,764 per square kilometre. Between 1997 and 2012, LSW witnessed rapid urban growth, with the highest rate of migration among all the Lum Luk Ka districts. In 2014, LSW was home to 117 small or medium-sized factories, 81 housing developments and 14 condominium projects.⁽³¹⁾ At present, there are two main roads that contribute to its urban development and transportation network. Highway 3312 runs east–west on the south side of the municipality; and the 3017 rural highway runs north–south in parallel with the Khlong 4 irrigation canal (Map 1). Around 2007, the upgrade of 3017 encouraged rapid residential development in LSW. In 2014, the Pathum Thani Rural Roads Office (PRRO) widened the 3017 road and installed an underground drainage system in response to the rapid increase in the urban built-up area in LSW.⁽³²⁾

Map 1

LSW municipality and its 11 villages

b. Village 5 case study background

Village 5, the largest of the 11 villages within LSW, had 24 per cent of LSW’s population in 2013 (Map 1), with 12,734 people and 6,613 households. For every 100 males there were 114 females.⁽³³⁾ Over the last 10 years, village 5 has experienced rapid development along the 3017 road, both residential and commercial. There are three main types of residential development: 1) subdivided land plots and shophouses, 2) old planned residential developments, and 3) new planned residential developments. We considered planned residential developments that occurred in the early 2000s as old developments, while those that occurred in the early 2010s and beyond are the new developments. These developments are situated within long and narrow land plots perpendicular to the 3017 road, a legacy of the former paddy fields.

V. Localized Flooding and Autonomous Adaptation

a. Localized flooding in Village 5 and its impacts

Within the past decade, communities and residents in Village 5 have experienced localized flooding related to rapid land development and failed drainage infrastructure. The village faces constant flooding, generally a mixture of stormwater runoff and sewage, and sometimes only sewage. Most low- and middle- income countries, including Thailand, tend to construct stormwater systems without separate provision for wastewater drainage, due to the high cost of construction. Stormwater runoff and sewage water thus travel within the same stormwater drainage system before being released into a water body without any prior treatment.⁽³⁴⁾ Localized flooding can occur over an extended period (i.e. three–six months) or many times a year, and it mostly appears as a shallow layer of standing water, enough to create difficulty in getting around and to present a hygiene concern to communities. We interviewed residents who suffered from localized flooding in the Roong-Rueng 2 housing development (RR2), Ruam-Sook subdivided land plots (RS1–RS10), and shophouses along the 3017 road (Map 2).

Map 2

Flooded area found in Village 5

Residents from these three locations have to endure stagnant floodwaters for a long period. Flooding in RR2 lasted for four months in 2014 before it was temporarily resolved by LSW. A sewage flood in RS7 and shophouse buildings was caused by failed underground piping along the 3017 road (Photo 1). Sewer floods in the dry season and combined sewer and stormwater floods in the wet season have negatively impacted residents’ wellbeing and the physical environment of Village 5. Foul-smelling stagnant floodwaters contain floating trash and quickly become pathogen-contaminated areas and mosquito breeding grounds. Local residents develop skin rashes from wading through contaminated floodwater. Children lose play areas in front of their houses. Prolonged flooding damages the road surface, causing ongoing difficulty for local residents. The study found that some residents in RR2 and RS4 had abandoned their houses, and one family in RR2 planned to move out in the near future if the problem remained unsolved.

Photo 1

Sewage flood in RS7

b. The drivers of localized flooding in Village 5

The root causes of localized flooding in the LSW municipality are intertwined. They are mainly related to arbitrary land development and institutional incapacity, where regulations are ineffective and organizational performance falls behind public expectations.

Rapid urban development

In cities with humid tropical climates and high intensities of rainfall during the rainy season, inadequate and poorly maintained drainage infrastructure can cause widespread flooding.⁽³⁵⁾ Since 2004 a large number of new housing developments have emerged in LSW,⁽³⁶⁾ most of them along the 3017 road. New urban development has caused an increase in the extent of impervious surfaces and a decrease of agricultural fields as well as diminished small water networks, leading to a large volume of surface runoff. This phenomenon has put enormous stress on poorly maintained stormwater drainage infrastructure, where it exists.

Malfunctioning or absent public road drainage infrastructure

In the past, the only public drainage network within this irrigated area was the irrigation canal system established in 1888. Later, when these irrigated fields were transformed into more urbanized areas, the roadside drainage system became an intermediate drainage network linking new urban built-up areas with the existing irrigation canal system. Roadside drainage ditches collect runoff from surrounding development areas before conveying this runoff to the irrigation canals. During rapid urban growth in LSW, new construction along the 3017 road illegally interrupted and altered the existing roadside drainage ditches. Despite the provisions of Highway Act B.E. 2535 (1992), which prohibit any transgression within the highways’ right of way, the Pathum Thani Rural Roads Office (PRRO) faces difficulties in enforcing those rules due to inadequate human resources for on-site controlling and monitoring. (See the supplementary information online for a table detailing the relevant legislation.) The transgressions can be identified as follows: replacing ditches with smaller culverts than those required, mismatching new culverts and the existing underground drainage infrastructure, and simply filling up ditches without replacing any culverts below. As a result, the 3017 road drainage system was a mixture of underground drainage pipes, often inadequate in size, and open drainage ditches, which do not work well together.

The poor maintenance of these roadside drainage ditches also contributed to occurrences of localized flooding. Some parts of the 3017 underground drainage infrastructure were damaged in Thailand’s great flood of 2011, and have not yet been properly repaired. Currently, only half an hour of normal rain can result in flooding 10–15 centimetres high in RR2, due to the combined problems of a failed drainage system within the development itself and the failed drainage system of the 3017 road in front of the development.⁽³⁷⁾ Illegal alterations to the drainage system by private actors and PRRO’s insufficient maintenance of 3017 roadside drainage ditches have interrupted the flow of water and led to localized floods on the road.

In addition to malfunctioning of public road drainage infrastructure, there are public roads within LSW built without stormwater infrastructure, which can increase risks of localized flooding when the surrounding areas are densely developed. In the rural areas of Thailand, it is normal to observe new public roads built without any provision of stormwater infrastructure, cutting through vast open fields that attract new urban developments to the area along both sides of the road. Initially these new developments do not face stormwater drainage problems, since abundant open space can absorb runoff. However, when these areas become densely developed due to urban encroachment, problems of localized flooding tend to occur. The involved agencies then start to upgrade the roads and construct stormwater infrastructure, which sometimes can create drainage conflicts between the existing drainage system in private developments and the newly installed public road drainage infrastructure. In LSW, mismatched levels between the new stormwater infrastructure of the 3017 road and existing stormwater infrastructure in private areas interrupted drainage efficiency and increased local flood risk.

Absent stormwater infrastructure in private developments

Another driver of localized flooding is the lack of stormwater drainage infrastructure on developed land. The earlier land developments in LSW, known as Ruam-Sook (RS) developments, were subdivided land plots with no infrastructure preparation. These RS developments take the form of 10 alleys located perpendicular to the 3017 road, running from the RS1 alley to the RS10 alley (Map 2). Currently four of these RS development projects have no stormwater infrastructure,⁽³⁸⁾ including RS4 and RS7 in Village 5. These RS developments always face localized flooding. This kind of subdivided land plot development without any provision for stormwater infrastructure is prohibited by the Land Subdivision Act, B.E. 2543 (2000). The planned residential developments since 2000 have been legally obligated to provide internal stormwater drainage infrastructure within the development area.

Inefficient management and irresponsible development

The sectoral approach and lack of coordination among agencies at the local, sub-regional and provincial levels are also drivers of localized flooding in LSW. The provision and maintenance of public infrastructure in LSW is the responsibility of different agencies under different ministerial lines with specific laws and regulations. The LSW municipality is responsible for the provision and maintenance of public drainage infrastructure within public properties, including local roads. PRRO is responsible for the 3017 road, including its drainage infrastructure, while SRIO supervises irrigation canals.

In addition to the fragmented responsibility and regulations, there was a problem of legal validation. The plots that were subdivided before 2000, when real estate laws and enforcement were still in their early stages, tend to face localized flooding problems due to the absence of drainage infrastructure. Although the Land Subdivision Act of 1972 was updated in 2000, land developments that occurred before 2000 did not have to comply with the act’s requirements. Localized flooding in LSW’s subdivided plots was the consequence of inadequate guidance from the old real estate laws. Currently, rules and procedures for land allocation are clear and enforced by the Provincial Land Subdivision Committee. However, the Land Excavation and Land Filling Act, B.E. 2543, issued in 2000, does not limit the height of land filling in new developments, but only requires a drainage system that does not cause flooding in adjacent areas (see the online supplement). This gap allows unrestrained land levelling in new planned residential developments to elevate the ground level of the entire property. This has the effect of placing neighbouring areas in low spots, which are prone to localized flooding instead.

The 3017 road upgrade by PRRO could also increase risks of localized flooding. Most of the land developments in LSW used the 3017 road level as their grading reference. However, this level is not stable because the whole 3017 corridor has been through several upgrades at different times. Any time 3017 was upgraded and elevated, older developments were left behind at a lower elevation. The study found a lack of communication and coordination among agencies involved in the latest upgrade of 3017 in 2015. Although PRRO is the main agency initiating redevelopment projects, three additional agencies are involved: the LSW municipality, the Provincial Waterworks Authority of Pathum Thani (PWA), and the Provincial Electricity Authority Rangsit (PEA). The municipality complained about missing information from PRRO on the new 3017 road elevation and limited opportunities to raise its concerns to PRRO.⁽³⁹⁾ PRRO also faced a problem of underground water supply pipe obstruction from PWA. Unlike PEA, which was notified early enough by PRRO to accommodate the new electricity system for the road, PWA did not get any notification and was unprepared to rearrange the water supply piping system. As a result, PRRO had to initiate an on-site construction adjustment scheme, in which the diameter of the public stormwater pipe was reduced, allowing for less stormwater volume from private developments compared to the original construction scheme.

Improper grading within planned residential developments also leads to localized flooding. In the old days, when LSW was a small sub-district with limited resources and weak enforcement, many developments took place without a proper land grading process. Developers tried to reduce costs by filling up the front of plots to match the existing road level, while leaving the back area of plots at a lower elevation (Figure 1).⁽⁴⁰⁾ When it rains, the back portion of these properties is always the first to be flooded. The national government has tightened the grip on these developments by improving the outdated law (Land Subdivision Act B.E., 2543 [2000]) and initiating a new law (Land Excavation and Land Filling Act, B.E. 2543 [2000]). As a result, LSW’s planned residential developments with an uneven land filling pattern are the remnant of irresponsible development from the past.

Figure 1

Improper grading can induce localized floods in the village

c. Actions by stakeholders that increase risks of localized flooding

Most drivers of localized flooding explained in Section Vb are the result of improper land development by private actors (land developers, community, and individual households) and improper spatial planning and infrastructure development by public agencies. Those actions of both private actors and public agencies that increase risks of localized flooding in the LSW municipality are summarized in Table 1. Localized flooding, caused by actions of various actors and poorly managed by local government, leads to autonomous adaptation undertaken by private actors, described in Section VI.

Table 1

Actions by stakeholders that increase risks of localized flooding

Affected area	Public agencies	Private actors
Irrigation canals	The South Rangsit Irrigation Office (SRIO) monitoring system is not efficient due to inadequate human resources and monitoring equipment.	Private actors illegally drain untreated wastewater into the irrigation canal.
Rural highways	The Pathum Thani Rural Roads Office (PRRO) upgraded the existing road surface and drainage system without enough coordination among involved stakeholders.	Private actors transgress roadside drainage ditches and underground drainage infrastructure when developing new construction (i.e. shophouses).
Municipality and public infrastructure	The local government is slow to initiate district-wide planning due to inadequate resources.	Although private actors follow rules and regulations, the absence of land use planning at the local level, as well as fragmented and incomprehensive rules in land use and construction guidance under different government agencies, increases gaps in stormwater drainage management and increases risks of localized flooding.
	Pathum Thani office of Public Works and Town and Country Planning (PPWTCP) has limited enforcement of land use policy against other government agencies whose activities affect land use characteristics (i.e. highway agencies, local government).
	Land Subdivision Committee of Pathum Thani (LSCP) granted permission to new planned residential developments without enough information on the existing stormwater drainage services and infrastructure. Many times, permits were granted to new developments located in areas without public stormwater drainage infrastructure.	Private developers can legitimately develop the land within an area where public stormwater infrastructure is absent if LSCP grants the permits.
	Local government faces difficulties in providing public drainage infrastructure for the public roads and the needed areas due to inadequate resources.	Private actors developed land located in areas without public stormwater infrastructure and adapted to anticipated flood risk by filling up the land at a high level or raising flood walls around the property.
	Due to the lack of planning policies and weak leadership, the LSW municipality built a new municipal road without provision of public drainage infrastructure.

The study found that both the LSW municipality and the provincial agencies in Pathum Thani were overwhelmed by the short-term coping measures to lessen localized flooding problems. At the same time, Bangkok has experienced increases in both the frequency and intensity of heavy rainfall events in recent decades, due to increased temperatures.⁽⁴¹⁾ Although climate change impacts are well recognized at the national level and by the city of Bangkok,⁽⁴²⁾ this awareness has not trickled down to the local governments in the BMR. Meanwhile, the current laws and regulations related to land use and water management under different government agencies serve only the mission of each agency under different ministerial lines of control, which do not acknowledge future threats of climate change. The LSW municipality and roads authorities have shown no recognition of future climate change scenarios. There is no evidence of a climate change agenda in any government development plans, either provincial or local, nor within the mission or vision statement of the Department of Rural Roads.

VI. Autonomous Adaptation and its Impacts

Although the negative impacts of localized flooding are obvious, the municipality’s responses have been slow and provisional. Therefore, local communities were forced to adapt by themselves (autonomous adaptation). To delineate and characterize local adaptation measures in the case study area, Table 2 summarizes the actions, outcomes and impacts of local adaptation undertaken by different types of private actors: individual households, the community, and the private sector. Individual households comprise residents of subdivided land plots, shophouses, and single houses outside planned residential developments. The community is the group of residents who reside in old planned residential developments abandoned by the developers without finishing the process of setting up the juristic person required by law. Thus, the residents have organized a housing committee to deal with localized flooding and other public facility issues. The private sector refers to developers and juristic persons whose actions affect the residents of the new planned residential developments.

Table 2

Autonomous adaptation measures undertaken by various types of private actors

Private actors	Adaptation measures	Outcomes	Impacts
			Private scale (private properties)	Public scale (public infrastructure)
Individual households	Built flood walls around the property.	Less water coming into houses. More water retained on street surfaces and drainage infrastructure.	Positive effect on individual households.	Negative effect: more runoff water flowing into the neighbouring areas that were at a lower level or did not have a flood barrier.
	Levelled the entranceways.	Less water coming into houses. More water retained on street surfaces and drainage infrastructure.	Positive effect on individual households.	Negative effect: more runoff water flowing into the neighbouring areas that were at a lower level or did not have a flood barrier.
	Dug up the public street surface to create a temporary drainage swale.	Floodwater subsided.	Positive effect on one individual but spread risks to other individuals.	Negative effect: the public road surface was damaged and interrupted the community’s mobility.
	Drained water out to an adjacent vacant plot.	Floodwater subsided. Water flowed into an adjacent vacant plot.	Positive effect on one individual but spread risks to other individuals.	No effects.
	Pumped water out of the property into public road drainage infrastructure.	Floodwater subsided. Water flowed into public drainage infrastructure.	Positive effect on individual households.	Negative effect: If this measure is widely practised at the same time, it could overload public drainage infrastructure and cause storm drains to overflow.
Community	Grouped together to file complaints with various agencies.	Government responded to the complaints by providing immediate coping measures.	Positive effect on the community.	No effects.
	Levelled the ground for the main entrance to an individual house.	Less water coming into houses. More water retained on a private street within the development.	Positive effect on one individual but spread risks of localized flooding to neighbouring areas within the same community.	No effects.
	Drained water to the adjacent property (vacant land plot, fishpond).	Floodwater subsided. Water flowed into the adjacent property.	Positive effect on one individual but spread risks to other individuals.	No effects.
	Pumped water out of the property into public road drainage infrastructure.	Floodwater subsided. Water flowed into public drainage infrastructure.	Positive effect on the community.	Negative effect: If this measure is widely practised at the same time, it could overload public road drainage infrastructure and cause storm drains to overflow.
Private sector	Levelled the land for the entire development’s property.	Less chance of flooding within the property area.	Positive effect on residents in the planned residential development.	Negative effect: this spread localized flood risks to others and could create more pressure on the public drainage system.
	Created an underground private drainage system by purchasing additional land and linking it directly with an irrigation canal.	Less chance of flooding within the property area.	Positive effect on residents in the planned residential development.	Negative effect: If this measure is widely practised at the same time, it could overload irrigation canal capacity to receive a large amount of stormwater in a short period.
	Pumped water out of the property into public road drainage infrastructure.	Floodwater subsided. Water flowed into public drainage infrastructure.	Positive effect on residents in the planned residential development.	Negative effect: If this measure is widely practised at the same time, it could overload public drainage infrastructure and cause storm drains to overflow.

Autonomous adaptations benefited those who took an active role, yet at the same time they spread risks to others. For example, in RS7 the individual household dug up the road surface to create a temporary open swale to drain floodwater into a neighbouring vacant plot (Photos 2A and 2B). This action created negative impacts at both the public and private scales. At the private scale, the adjacent vacant plot was waterlogged. At the public scale, the damaged road surface interrupted the community’s mobility and the waterlogged vacant plot could become a mosquito breeding ground, which will affect surrounding neighbours’ health.

Photos 2A and 2B

Autonomous adaptation by an individual household damaged the public road surface (A) and drained water out to an adjacent vacant plot (B)

Land developers’ land levelling in new planned residential developments can increase the risk of localized flooding in the neighbouring land areas (Figure 2). As planned residential developments in LSW continue to grow, the risk of localized flooding in old residential neighbourhoods tends to increase. With limited resources and authority, the LSW municipality could only cope and adapt to the situations with provisional measures such as filling up the flooded areas with gravel, creating an underground private drainage system, and pumping water out of property. These measures were effective within a limited area and were provisional, similar to those initiated by private actors.

Figure 2

Land filling by new developments imposes localized floods on neighbours

In term of social measures, the study found that the municipality responded to the complaints from well-organized groups of actors faster than those raised by individual households. After suffering prolonged localized flooding and filing several complaints to the municipality, with help from the village headman, the RR2 housing committee lodged a complaint with the military officer appointed by the National Council for Peace and Order (NCPO). The meeting with the deputy mayor, village headman and housing committee was held with the military officer, who acted as an intermediary. Finally, the municipality took action by initiating the temporary measures described in the previous paragraph. Unlike with the RR2 community, RS7’s filing of complaints did not lead to actions by the municipality. As a result, one individual household decided to undertake autonomous adaptation by digging up the road surface, as described earlier in this section.

The consideration of the advantages and disadvantages of autonomous adaptation depends on one’s perspective. Autonomous adaptations benefit individual households, communities, and the private sector, but they create negative impacts on public infrastructure and weaken the public stormwater system, as well as inducing tensions among actors. Some measures have already created negative effects on the environment and the community’s wellbeing, and some measures will increase the risks of local floods in the near future. Inadequate and inefficient official intervention has forced private actors to invent their own flood adaptation measures, which later could cause the entire public drainage system to fail. Autonomous adaptation at any scale tends to involve distributing risks to others, as excess water is drained outward onto public road surfaces or towards other open spaces nearby, which are likely to be developed soon. In the near future, as Village 5 reaches a mature stage of urbanization, localized flooding is to be expected.

VII. Discussion and conclusions

This paper investigates the drivers and impacts of localized flooding in the peri-urban area of a mega-city and explores how autonomous adaptation affects the local environment and community wellbeing. Localized flooding is triggered by multiple drivers associated with: rapid increase of the impervious surface within an urbanized area, malfunctioning or lacking drainage infrastructure in both private developments and public roads, irresponsible land grading in private development, and uncoordinated public infrastructure development between public agencies.

Rapid urban growth in LSW exhibits a common characteristic of EMRs: public services lagging far behind new construction.⁽⁴³⁾ New developments in LSW have occurred rapidly without sufficient guidance or enforcement. An irresponsible and haphazard development with inadequate and inefficient stormwater infrastructure have caused localized flooding. In line with previous studies of urban flooding,⁽⁴⁴⁾ drivers of localized flooding in LSW include: a rapid increase of urban built-up spaces within flood-prone areas, limited and poorly maintained drainage infrastructure, violation of laws, and weak local government. Violations of laws and regulations on land development and construction in LSW took the form of damage to public drainage infrastructure and illegal site grading. The municipality’s slow response to flooding problems and its provisional flood coping measures are examples of inept management, which can then encourage autonomous adaptation on the part of individual households, communities, and the private sector.

A lack of coordination between old and new urban development, and among different levels of governmental authority, also triggers localized flooding, as in the example of uneven grading. Fast urban expansion forces local government to provide public service immediately, without enough prior planning and guidance. The municipality’s administrative structure, which is incapable of meeting basic needs, can instigate autonomous adaptation at the local level. Development of public roads by the LSW municipality in response to rapid urban growth increases risks of localized flooding because there is no provision of public stormwater infrastructure on the road or any stormwater drainage management planning. Thus, the findings from this study are in line with the argument that weak urban governance drives individuals and businesses to develop independent responses to natural hazards and leads to maladaptation.⁽⁴⁵⁾

Adaptation measures similar to those documented in previous studies of peri-urban poor communities⁽⁴⁶⁾ were found in LSW communities, in terms of both physical and social measures. Externalities of adaptation in peri-urban poor communities are often positive. Efforts, knowledge and resources, shared among community members, encourage potential upscaling in working with local governments. However, autonomous adaptations undertaken by private actors in LSW generated tensions among stakeholders.

Autonomous adaptation by the private sector increases vulnerability of communities and individual households. This finding is in line with previous studies, which argued that flood risk reduction in one settlement can increase flood risk in others.⁽⁴⁷⁾ Any local coping and adaptation strategies that divert risks and impacts in time and space, and create severe impacts on others, are considered maladaptation.⁽⁴⁸⁾ In terms of social measures, the study found that the municipality responded to the complaints from well-organized groups of actors faster than those raised by individual households.

The findings suggest that policymakers and government agencies who work in peri-urban areas of mega-cities in low- or middle-income countries should take a closer look into the root causes of localized flooding while addressing the immediate flood threats to communities. The establishment of local planning guidance and a local drainage plan is strongly recommended. Spatial planning and stormwater drainage management, engaging different levels of agencies in charge and drawing on community perspectives, will minimize the risk of localized flooding and maladaptation. Although this research focuses on negative externalities from autonomous adaptation, it is necessary to search for an institutional mechanism that would enhance the positive side of collective adaptation and inclusive urban stormwater governance.

This local case study reflects the necessity of adaptive and responsive local governance to strengthen Thailand’s urban climate governance at regional and national scales. Further comparative case studies on different sites within Pathum Thani irrigated fields as well as other sections of the BMR, where the historical context of land use might be different, would enhance the findings. Overall, additional research on stormwater governance is necessary to achieve more sustainable stormwater management in the dynamic context of peri-urban areas in developing countries under a changing climate.