Quantifying the Spatiotemporal Pattern of Urban Expansion and Hazard and Risk Area Identification in the Kaski District of Nepal

Rimal, Bhagawat; Zhang, Lifu; Keshtkar, Hamidreza; Sun, Xuejian; Rijal, Sushila

doi:10.3390/land7010037

Cited by 49 publications

(44 citation statements)

References 61 publications

(106 reference statements)

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“…On-ground field assessment to monitor and model LULC change in large areas is often not practical, whereas the use of remote sensing and GIS tools can be quite effective [40,41]. Spatio-temporal observations using remote sensing and GIS techniques [42] allow researchers to obtain time-sensitive data to analyze LULC change in urbanizing contexts [43] and project future land-use change [44,45].…”

Section: Methodsmentioning

confidence: 99%

“…All Landsat scenes were obtained from the United States Geological Survey (USGS) website (https://earthexplorer.usgs.gov) ( Table 1). Landsat SR data underwent post-production processing entailing geometric rectification, atmospheric correction and other processing (for more details, http://landsat.usgs.gov/CDR_LSR.php), rendering data suitable for scientific analysis [29,40,46,47] The SR data product includes quality assessment (QA) bands used here to identify and omit pixels with snow, clouds and cloud shadows. Geometric accuracy was verified for all satellite images, which were projected to the UTM projection (datum WGS 1984).…”

Section: Data Processing and Analysismentioning

confidence: 99%

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Urban Expansion Occurred at the Expense of Agricultural Lands in the Tarai Region of Nepal from 1989 to 2016

et al. 2018

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Recent rapid urbanization in developing countries presents challenges for sustainable environmental planning and peri-urban cropland management. An improved understanding of the timing and pattern of urbanization is needed to determine how to better plan urbanization for the near future. Here, we describe the spatio-temporal patterns of urbanization and related land-use/land-cover (LULC) changes in the Tarai region of Nepal, as well as discuss the factors underlying its rapid urban expansion. Analyses are based on regional time-series Landsat 5, 7 and 8 image classifications for six years between 1989 and 2016, representing the first long-term observations of their kind for Nepal. During this 27-year period, gains in urban cover and losses of cultivated lands occurred widely. Urban cover occupied 221.1 km 2 in 1989 and increased 320% by 2016 to a total 930.22 km 2 . Cultivated land was the primary source of new urban cover. Of the new urban cover added since 1989, 93% was formerly cultivated. Urban expansion occurred at moderately exponential rates over consecutive observation periods, with nearly half of all urban expansion occurring during 2006-2011 (305 km 2 ). The annual rate of urban growth during 1989-1996 averaged 3.3% but reached as high as 8. 09% and 12.61% during 1996-2001 and 2011-2016, respectively. At the district level, the rate of urban growth and, by extension, agricultural loss, were weakly related to total population growth. Variability in this relationship suggests that concerted urban-growth management may reduce losses of agricultural lands relative to historic trends despite further population growth and urbanization. Urbanization and LULC change in the Tarai region are attributable to significant inter-regional migration in a context of poor urban planning and lax policies controlling the conversion and fragmentation of peri-urban cultivated lands. Urban expansion and farmland loss are expected to continue in the future.

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Section: Methodsmentioning

confidence: 99%

Section: Data Processing and Analysismentioning

confidence: 99%

Urban Expansion Occurred at the Expense of Agricultural Lands in the Tarai Region of Nepal from 1989 to 2016

et al. 2018

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“…They are effectively used for the LULC analyses [4,[30][31][32][33][34], and flood area mapping. The Birendranagar city spans Nepal's sub-Himalayan and lesser-Himalayan zones, which are characterized by a warm-moist temperate, hot-dry sub-tropical, warm-dry sub-tropical, and cool-moist temperate climates, with annual temperatures ranging from 10 • C to 30 • C [22].…”

Section: Extraction Of Lulc Changementioning

confidence: 99%

“…Floods are the most common and devastating natural hazards [6] on a global scale and have been increasingly frequent and devastating since the mid-20th century [4]. Of all flood events recorded between 1950 and 2011, most have occurred during recent decades.…”

Section: Introductionmentioning

confidence: 99%

“…Here, urbanization is understood as processes leading toward increased population density, socioeconomic activities, and expanded built up areas and associated infrastructures [2]. Natural hazards and urbanization can interact to amplify land-use change, such as that negatively affecting agricultural areas [3,4]. In hazardous areas, including newly formed urban areas, land management and planning that would enhance resilience depend therefore on an understanding of those land-use/land-cover change (LULC) patterns that accentuate latent hazards [5].…”

Section: Introductionmentioning

confidence: 99%

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Flood Hazard Mapping of a Rapidly Urbanizing City in the Foothills (Birendranagar, Surkhet) of Nepal

Rijal

Rimal

Sloan

2018

Land

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Flooding in the rapidly urbanizing city of Birendranagar, Nepal has been intensifying, culminating in massive loss of life and property during July and August 2014. No previous studies have monitored underlying land-cover dynamics and flood hazards for the area. This study described spatiotemporal urbanization dynamics and associated land-use/land-cover (LULC) changes of the city using Landsat imagery classifications for five periods between 1989 and 2016 (1989-1996, 1996-2001, 2001-2011, 2011-2016). Areas with high flood-hazard risk were also identified on the basis of field surveys, literature, and the Landsat analysis. The major LULC changes observed were the rapid expansion of urban cover and the gradual decline of cultivated lands. The urban area expanded nearly by 700%, from 85 ha in 1989 to 656 ha in 2016, with an average annual growth rate of 23.99%. Cultivated land declined simultaneously by 12%, from 7005 ha to 6205 ha. The loss of forest cover also contributed significantly to increased flood hazard. Steep topography, excessive land utilization, fragile physiographic structure, and intense monsoonal precipitation aggravate hazards locally. As in Nepal generally, the sustainable development of the Birendranagar area has been jeopardized by a disregard for integrated flood-hazard mapping, accounting for historical land-cover changes. This study provides essential input information for improved urban-area planning in this regard.

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Himalayan hazard cascades – modern and medieval outburst floods in Pokhara, Nepal

Fischer

Lehnigk

Lützow

et al. 2023

Earth Surf Processes Landf

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In May 2012, a sediment‐laden flood along the Seti Khola (= river) caused 72 fatalities and widespread devastation for > 40 km in Pokhara, Nepal's second largest city. The flood was the terminal phase of a hazard cascade that likely began with a major rock‐slope collapse in the Annapurna Massif upstream, followed by intermittent ponding of meltwater and subsequent outburst flooding. Similar hazard cascades have been reported in other mountain belts, but peak discharges for these events have rarely been quantified. We use two hydrodynamic models to simulate the extent and geomorphic impacts of the 2012 flood and attempt to reconstruct the likely water discharge linked to even larger medieval sediment pulses. The latter are reported to have deposited several cubic kilometres of sediment in the Pokhara Valley. The process behind these sediment pulses is debated. We traced evidence of aggradation along the Seti Khola during field surveys and from RapidEye satellite images. We use two steady‐state flood models, HEC‐RAS and ANUGA, and high‐resolution topographic data, to constrain the initial flood discharge with the lowest mismatch between observed and predicted flood extents. We explore the physically plausible range of simplified flood scenarios, from meteorological (1000 m3 s−1) to cataclysmic outburst floods (600,000 m3 s−1). We find that the 2012 flood most likely had a peak discharge of 3700 m3 s−1 in the upper Seti Khola and attenuated to 500 m3 s−1 when arriving in Pokhara city. Simulations of larger outburst floods produce extensive backwater effects in tributary valleys that match with the locations of upstream‐dipping medieval‐age slackwater sediments in several tributaries of the Seti Khola. Our findings are consistent with the notion that the medieval sediment pulses were linked to outburst floods with peak discharges of >50,000 m3 s−1, though discharge may have been an order of magnitude higher.

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Quantifying the Spatiotemporal Pattern of Urban Expansion and Hazard and Risk Area Identification in the Kaski District of Nepal

Cited by 49 publications

References 61 publications

Urban Expansion Occurred at the Expense of Agricultural Lands in the Tarai Region of Nepal from 1989 to 2016

Urban Expansion Occurred at the Expense of Agricultural Lands in the Tarai Region of Nepal from 1989 to 2016

Flood Hazard Mapping of a Rapidly Urbanizing City in the Foothills (Birendranagar, Surkhet) of Nepal

Himalayan hazard cascades – modern and medieval outburst floods in Pokhara, Nepal

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