Spatial Assessment of 2014-ood Disaster and Extent of Associated Damages in Lower Chenab Basin, Upper Indus Plain, Pakistan

This study is an effort of spatial assessment of 2014-ood and associated damages in Upper Indus Plain (UIP). Community Based Disaster Risk Management (CBDRM) approach in integration to geo-spatial techniques is implemented to assess the nature and damages as well as community perception in reducing oods. In this regard, a semi-structured questionnaire was designed for micro-level detail investigation. A total of 422 households were surveyed in 22 ood affected villages in eight districts forms the lower Chenab Basin using random sampling techniques. Secondary data regarding river discharge is collected from Regional Meteorological Centre, Lahore. Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM) having 30m spatial resolution and Landsat satellite image of September 2014 with same resoluation is acquired from open source geo-database of United States Geological Survey (USGS). Landsat satellite image is processes to extract the spatial extent of inundation. Watershed modelling approach is utilized to demarcate Chenab River Basin in GIS environment. Buffer analysis and Inverse Desistance Weighted (IDW) technique of spatial interpolation are used to geo-visualize the spatial extent and depth of ood based on community perception. Analysis reveals that ood is one of the recurring phenomena in Chenab Basin. The upper catchment areas of Chenab Basin are dominated by ash oods and low-lying areas are prone to riverine oods. The 2014-ood has caused estimated economic damage of 1409.295 million Pakistani Rupees (mPKR). Housing sector suffered the major losses of more than 1000mPKR followed by agricultural sector. Based on spatial extent, vertical prole and damages the study region is categorised into upper and lower zones. The lower zone is most affected in terms of extent, depth and damages. This study can assist the decision makers and disaster managers in designing location specic ood risk reduction.


Introduction
Worldwide, ood is one of the worst hydro-meteorological disasters causing socio-economic, environmental and physical damages (Rahman & Khan 2011;. Commonly, heavy rainfall accompanies by melting of snow and glaciers leading to oods. Its further development is in uenced by intensity of rainfall, hydrological response and geo-morphometric character of the basin . Meteorologically, rising intensities of heavy rainfall events are increasing the frequency and magnitude of oods (Booij 2005). Similarly, excessively melting of snow and glaciers due to rising global temperature (Kosaka & Xie 2013) and clearing of green cover further intensi ed the phenomena (Gholami et al. 2009;Rahmen & Khan 2013).
The risk of climate change has increase the ood risk (Hirabayashi et al. 2013). It is also clear from the recent scienti c literature that the frequently occurring extreme precipitation episodes will increase the devastating oods . The rainfall directly contributes water to the drainage system in basin (Dawood et al. 2020). In this perspective, trend in rainfall has signi cant impact on genesis of oods (Beyene et al. 2010). The current climate change exacerbation has been a major concern due to its projected impacts on socio-economic and physio-ecological system (Vetter et al. 2017). However, number of anthropogenic activities turn the oods more destructive (Dong et al. 2009). The impacts of oods on a global scale are enormous (Jonkman et al. 2008). Annually, ood disaster is resulting in over 20000 life loss and re ective property loss (Mahmood & Razia 2018).
During the 20th century, oods have taken lives of 8 million people (Jonkman 2005). The ten disastrous oods from 1980 to 2010 has caused 13393 fatalities and 149600 million US$ losses (Mahmood et al. 2016a).
In Pakistan, high magnitude oods were more frequent particularly in the last two decades due to diversity in hydro-meteorological and geographical conditions (Mahmood et al. 2016b; Mahmood et al. 2019a,b). The heavy Monsoon rainfall and melting of snow/glaciers in the mountainous north generate oods (Shamshad 2011;Houze et al. 2011). The Monsoon contributes about 60-70% in total rainfall (Kakar 2010;Wang et al. 2011;Hashmi et al. 2012;Hussain & Lee 2014). Temporally, this season extends from June to September with maximum rainfall in July and August resulting in damaging oods (Rahman and Shah 2012). The extraordinary activity of Monsoon, poor preparedness and lack of suitable ood mitigation structural measures in the Indus Plain are leading to devastating oods (Zaman & Afzal 2013;Khan et al. 2014;. Consequently, the individual, household and community vulnerabilities have been grown (Ouma and Tateishi 2014). The varying demographic conditions, socio-economic status and human economic activities in the proximity of active ood plain have further intensi ed vulnerability to oods leading to high risk (Aggarwal 2016;Mahmood and Hamayon 2021).
In the year 2010, a disastrous ood hit the country and anthropogenic activities over the past years in Indus Plain further strengthen the damaging charater of ood and caused human life losses, damages to buildings, infrastructure and agricultural sector with huge economic loss (Hauze et al., 2011;Mahmood et al., 2016a,b). More than 1850 people lost their precious lives, tens of billions US$ economic loss occurred, affected above 20 percent of the total land area and about 15 million people (Mahmood 2019). The spatial extent, depth and duration of ood with direct effect was uneven because of spatial variation in landscape, land use/Land cover and population density . Likewise, in the year 2014, extraordinary activity of late Monsoon (September) caused massive ood in upper Indus Plain particularly in lower Chenab Basin. The recorded peak was 0.45 million cusecs with physical and economic damages. These were the most destructive oods in Pakistan (Mahmood and Razai 2018). The surface hydrology of Indus Basin, spatial extent of 2010-ood, damages and causative factors of ooding have already been published and discussed by number of researchers few are (Gaurav et al. 2011;Manzoor et al., 2013;Syvitski and Brakenridge 2013;Arslan et al. 2013;Khan et al. 2014). Hashmi et. al. (2012 carryout a detail study on carring capacity of rivers and barrages in Pakistan. He also nout the role barrages and inundation canals in ood mitigation.  assessed the 2010-ood causative factors and spatial extent of damages in central Indus Basin.  also assessed the cause and damages of the 2010-ood disaster in Central Indus Basin. In this study, 2014-ood ood disaster and the extent of associated damages in upper Indus Plain are spatially assessed using integrated geo-spatial techniques and Community Based Disaster Risk Management (CBDRM) approach. Place-based concept of vulnerability is used to investigate the nature of past oods as suggested by (Mahmood and Hamayon 2021). For detail micro-level analysis, 22 ood affected villages were randomly selected from eight districts located spatially distributed over the right and left banks of Chenab River in 8Km buffer zone.
Based on community perception, ood depth, its spatial extent and socio-economic conditions were analysed.
Alongside, hydrological behaviour of the river during ood is visualized. The integrated approach of Geographic Information System (GIS), satellite data, Global Positioning System (GPS) and eld surveys are used as monitoring tools in the process of spatial assessment for gei-visualization of ood and associated damages.

The Study Region
Geographically the Lower Chenab Basin extends from 30°36' 7.2"N to 32°49'40.8"N latitude and 73°43'40.8"E to 74°57'3.6"E longitude. Administratively, the study region includes the districts of Gujrat, Sailkot, Gujranwala, Mandibahudin, Sarghodha, Ha zabad, Chinot and Jhang. The research of Chenab River extends from Head Marala is located in the north to Head Trimmu in the south (Fig. 1). Chenab River is one of the main eastern tributaries of Indus River System which undergoes intensive inundation almost every year during the late monsoon period (Ali, 2013). The length of Chenab River is 274Km in Pakaistan. The total catchment area Chenab Basin is 41656Km² out of which 27195Km² is mountainous catchment area in upstream of Head Marala which is dominated by ash oods and lowlying areas are characterised by riverine oods. It enters Pakistan at Marala Headwork with annual average discharge of 26.7 million acre feet (MAF). The mean monthly water discharge is above 62000 cusecs in July and August while in September is less than 50000 cusecs (Mahmood and Razia, 2018 ).
The Upper Indus Palin is a fertile land that supports the livelihood of millions of people. They are engaged in variety of economic activities particularly agriculture. Agricultural activities are successful with maximum production because of the availability of fertile alluvium and canal irrigation system. Therefore most of the local residents have their source of revenue from agricultural activities. The major cultivated crops are rice, sugarcane, maize, cotton, fodder and beans. Mostly, people are living in bricks and mud houses which are non-resilient to ood. The housing condition and lower per month income has made the exposed communities susceptibility to oods.

Data Acquisition And Analysis
Community Based Disaster Risk Managemnt (CBDRM) approach in integration with Geo-spatial techniques is implemented to spatially assess the 2014-ood disaster and associated damages. In this regard, a semi-structured questionnaire was designed for micro-level detail investigation of socio-economic conditions of the residents in ood zone, nature of ood and community perception regarding ood risk reduction in order to minimize future damages. The respondents were asked regarding the socio-economic effects of oods. Consent of every respondent was taken prior to questions. Before the detail eld investigations a preliminary survey was conducted in the study region to determined the spatial extent of ood and check the validity of questionnaire. There is nothing related to bioethics therefore ethical approval is not applicable for this study.
Based on preliminary survey results sample villages were selected randomly in de ne spatial extent (8Km buffer zone) of ood based on community perception. The sample villages were randomly selected from eight (100%) ood effected districts in lower Chenab Basin (Fig. 1). The sample villages are spatially distributed along River Chenab over left and right banks from Head Marala to Head Trimmu. A total of 422 households were surveyed by simple random sampling technique in the 22 ood effected villages in 8Km buffer zone. During questionnaire survey the respondents were asked regarding the socio-economic conditions, nature and damages of ood. The socio-economic conditions included age, family size, income and expenditure. Nature of ood included depth, frequency, spatial extent and duration of ood. Damages included damages to houses, standing crops, loss of livestock and agricultural equipments. The respondents were also asked about the estimated rehabilitation cost of damages to determine the total economic loss. The respondents were also asked regarding the ood risk reduction strategies using CBDRM approach.
Secondary data is collected from concerned government departments. Historical record of river discharge is collected from Regional Meteorological Centre, Lahore. The data about affected population, human casualties, livestock casualties, houses damages and crops affected were obtained from Punjab Provincial Disaster Management Authority (PPDMA).
Watershed modelling approach is utilized to delineate Chenab watershed in GIS environment by using SRTM spatial data as input layer. Buffer analysis technique and CBDRM approach is applied in integration to delineate the spatial extent of ood. Similarly, Inverse Distance Weighted (IDW) technique of spatial interpolation is applied in integration with community perception to model ood depth in de ned spatial extent. Descriptive statistical technique is used to process and analyze damages data. Average rehabilitation cost in every sector for one unit is calculated. Then total estimated economic loss is calculated by adding damages in all sectors in million Pakistani Rupees (mPKR). Flood extent was extracted from Landsat satellite image by maximum likelihood image classi cation technique in GIS environment. The results are presented in the form of maps, tables and graphs.

Results And Analysis
Riverine oods are more destructive over the Indus Plain because of the fairly at surface, high population density and dense human economic activities particularly agriculture (Tariq and Giesen 2012). The frequency of extream rainfall events with 150mm/day or higher presented a signi cant positive tendency indicating high risk of potential oods (Ahmad et al. 2015). The study region is also the part of UIP where the spatial assessments of 2014 ood disaster and its associated damages have been made. The details are given in the following sections.

Socio-economic status of the Surveyed Households
The total population of the surveyed households was counted as 3749 persons. Family size of the households is separated into three categories; small, medium and large. The family comprised of parents (father and mother), their kids, niece, nephews, grandfather and grandmother. Medium size families (6 to 10 persons) were around 55.6 percent, while small (less than 6 persons) and large size families (more than 10 persons) were 18.4 percent and 26 percent, respectively. The average family size of the surveyed households was 9 persons with a standard deviation of 5. Likewise, the monthly income of the surveyed households was categorized into three classes i.e. "low income class" <15,000 Pakistani Rupees (PKR), "middle income class" ranging from 15,000-25,000 PKR, and "high income class" >25,000 PKR. Out of the total surveyed households 58.3 percent were belong to low income class, around 22.9 percent were of middle income and 18.8 percent were in high income class. More than 90 percent of the respondents were living in mud houses. These non-resilient houses were constructed in ood zone.

Genesis of 2014 Flood Disaster
The spatial pattern of Monsoon rainfall varies across the country from August to September. The Chenab Basin is spatially located in zone having daily average rainfall of 3mm per day. But in the year 2014, the extra ordinary activity of the late ( rst week of September) Monsoon rainfall particularly over the upper catchment areas of Chenab Basin ( Figure 2C) generated high surface runoff and high discharge in rivers. Rain-water together with melt-water in the eastern rivers of Indus System, particularly in Chenab River, resulted in massive ood at Head Marala extraordinary scale, both in terms of magnitude and spatial extent. Along with this heavy runoff, India also released 0.2million cusecs in the upper catchment area of Chenab River which has caused massive inundation in Lower Chenab Basin (Head Marala to Head Trimmu) with devastating effects. The out ow from Head Marala coupled with runoff from local Nullahs (streams) heightened the ood peak upto 0.95million Cusecs. This unexpected peak hit the Khanki Barrage (designed capacity of 0.8million cusecs) on 7th of September, 2014 early morning. The Punjab Irrigation Department (PID) took a decision to breach the bund (embankment) in order to reduce the risk barrage outburst because the ood peak was high than its capacity. The breaching decision was effective because ood water re-entered the river channel without life loss and damages. The ood peak of 0.95million Cusecs was owing downstream and hit Head Qadirabad (designed capacity of 0.8million cusecs) at 11:00am on same day. The Trimmu Headworks (designed capacity of 0.645million cusecs) received ood peak of around 0.703million cusecs on 10th of September at 07:00pm. The planned breaching segment in Right Marginal Bund (RMB) was activated on 10th of September at 10:00am as per policy. The Jhang Flood Protection Bund situated along left bank of Chenab River was burst by the hydraulic pressure of ood peak over two spots resulting in around 0.07 to 0.075million cusecs ood ow to passed through the breached segments. Finally, high ood stage of 0.455million cusecs was documented in Chenab River at Panjnad on 16th of September (Figure 3). The runoff in ordinary oods remains less than 0.1million cusecs whereas above 0.6million cusecs are unusually high ood. The highest runoff in River Chenab at Head Marala was 0.543million cusecs, at Head Qadirabad 0.556million cusecs and at Head Khanki 0.66million cusecs. Therefore, ood in 2014 was announced as high ood stage in lower Chenab Basin.
Consequently, this high ood has damaged standing crops, lifeline infrastructure and villages in the ood zone affecting national economy directly and indirectly badly. Based on the accessible data and estimations, the 2014ood affected approximately 2.6million people, completely or partially damaged 1.3million houses and took 387 precious human lives in Chenab Basin. In agricultural sector, about 0.25million farmers were affected, more than one million acres of cropland with standing cash crops and fodder crops were severely damaged from north (Marala Headworks) to south (Trimmu Headworks) in lower Chenab Basin.

Spatial Extent and Depth Level of 2014-Flood
The spatial extent of 2014-ood was variable from Marala Headworks to Trimmu Headworks in the lower Chenab Basin. The extent of ood increases downstream from Sialkot to Jhang (Fig. 2). The northern region comprised of Gujrat, Sialkot, Gujranwala and Mandi Bahauddin districts with spatial extent of ood ranging from 0.4 to 0.7km.
The southern region includes districts of Ha zabad, Chinot and Jhang. The spatial extent in Ha zabad was 4.2Km and Jhang 4km. In Jhang, the estimated spatial extent is on left bank is 3.4km while over the right bank 1.2km. In Sarghodha, extent is minimum (Figure 3).
The spatial variation in ood depth level is also an essential output of the hydrological modelling approach. The vertical pro le is important in determining vulnerability to ood. It depends on uvial morphology and hydraulics of the river channel. In general, the ood depth level is higher in the active channel and lowers towards the banks.
The ood depths futher decreases in the inundated areas on both sides depending on the local landscapes. In the selected reach of Chenab River in lower Indus Plain, the vertical pro le of the ood is minimum (less than 1.5m) in the northern section of the reach because of low discharge. In the middle section, depth level is variable because of wetted width of active channel and variation in morphology of the channel bed where depth is ranging from 1.5m to 3m. The southern section has maximum ood depth ranging from 3m to 4m and above. Spatially, ood depth is minimum in Sialkot and Gujrat and maximum in Chinot (3m-4m) and Jhang (4.2m; Figure 4). GIS base ood depth mapping provides a clear picture across and along the river channel. Figure 5a,b is visualizing the pre and post ood conditions of the study region. It is evident from the satellite image that the spatial extent of ood is expanding towards south.

Extent of Associated Damages
The spatial extent, depth and duration of ood have affected communities in the hazard zone. Life losses, damages to human settlements, agricultural sector in the proximity of river were more drastic. The ood damages have been spatially assessed through GPS based questionnaire survey, observations and interviews in the eight selected sample districts. In the entire study region, ood has affected population from north to south. Although the number of affected people directly or indirectly varies. In Sarghodha, affected population is less than 10000. In Gujrat, Sialkot and Gujranwala the affected population is ranging from 10000-20000 whereas in Jhang more than 40000 people is affected by ood ( Figure 5).
Flood has also caused fatalities in the entire study region from north to south. In Gujranwala, Mandi Bahauddin and Sarghodha human losses were minimum whereas in Sialkot it is maximum ( Figure 6). In Chinot and Jhang ijuries are maximum due to the maximum spatial extent and depth of ood. Damages to houses are also more because more than 95% are mud houses which are non-resilient to ood. The spatial extent and depth of ood has affected human settlements badly (Fig. 7). It has damaged houses completely as well as partially. In Jhang (456), Chinot (426) and Ha zabad (393) the completely damaged houses are more whereas partially damaged are also high in Chinot (1531) and Jhang (1620).
In the study region agriculture is main economic activity of the people due the availability of fertile soil and irrigation facility. The 2014-ood has badly affected agriculture sector. During ood, standing crops particularly cotton, rice and sugarcane were prepared to yield. These ready to harvest crops were severely damaged by disastrous inundation. Widespread damages (> 40mPKR) to agricultural sector were reported in the districts of Jhang, Gujrat, Chinot and Ha zabad (Table 1) because crops were inundated by ood and damaged it completely. Damages to standing crops badly affected the farmer's income level as well as having negative consequences on overall agricultural production. Mahmood and Razia (2018) also narrated that 2014-ood has caused reduction in crop production mainly in rice and sugarcane by 0.217million ton and 0.726million tons respectively. Similarly huge quantity of cotton bales was lost. Beside this, damages to agricultural equipment and loss of stored seeds affected the sector. Likewise, irrigation channels were breached by ood or blocked by siltation which has further affected the agriculture sector.
In the entire study region, livestock is a source of income as well as accomplish the food and nutrition needs of the households. The livestock sector was also severely affected by ood due to signi cant losses. On the whole, more than 2000 small and large livestock were lost due to ash oods in the upstream areas whereas in lower Chenab Basin ood has caused loss of Buffalos (332), cows (156) and goats (170).

Sector Wise Estimated Economic Loss
The disastrous ood of 2014 has caused damages to human life, structures and properties. The total estimated rehabilitation cost was 1409.295 mPKR. Sector wise detail of the ood damages are given in table 1, which shows that that housing sector suffered the major losses of more than 1000mPKR followed by agricultural sector with maximum losses to standing crops. Similarly, according to NDMA (2014) ood has caused damages of 180.52 mPKR to disaster resilience infrastructure (Table 1).

Community Based Flood Risk Management
The Community Based Disaster Risk Management (CBDRM) Approach is applied for possible ood risk reduction strategies. In this regard, response of the community was healthy. The community perception regarding ood risk reduction was valuable because of indigenous knowledge. Out of the total respondents, 46% suggested that embankments at suitable location will reduce the risk of ood in the study region (Table 2). Both constructions of embankments and digging of inundation canals have been suggested by 19% of the surveyed households. 12.5% respondents were of view that construction of multipurpose barrages will reduce the risk of ood as well as store water during ood season. Widening and deepening of existing canals is suggested by 7.5% respondents.
Plantation in upper catchment areas and along river and canals is suggested by 11%.

Discussion
Analysis revealed that Pakistan is prone to hydro-meteorological disasters particularly oods (Mahmood 2019). The 2014-ood is generated by the extraordinary late Monsoon activity over the Chenab Basin with rainfall intensity of 18mm per day during wet spell which is much higher than the daily average (3mm per day) of the 46 years for the September. Floods have been common and devastating causing damages to lives, properties, standing crops, infrastructure and services (Rahman & Khan 2011;Mahmood et al. 2016a). So far, 25 major oods have occurred in Pakistan since 1950 whereas in the past two decades the frequency of high ooding events has been increased (Hashmi et al. 2012;Mahmood and Rahman 2019). As a result, individual, household and community vulnerabilitiy have been heightened (Aggarwal 2016). The changing demographic conditions, socioeconomic status and human economic activities in the ood zone have further intensi ed the vulnerability to oods (Ouma and Tateishi 2014). So, the rising magnitude of ood hazard and socio-economic, physical and attitudinal vulnerabilities has uplifted the ood risk . Heavy rainfall in monsoon season and melting of snow/glaciers in northern Pakistan (mountainous north) are ood generating factors (Khan 2005;Houze et al. 2011;Shamshad 2011) whereas the poor preparedness and location speci c standard structural measures in Indus Basin compel the ood dealing authorities to breach the emabankement in order to protect barrages and main cities .
Analysis also revealed that on average the monthly income of the household is less than 20000PKR. More than half of the households have monthly income less than 15000PKR. Similarly, about 18.4 percent of the households have small family size. More than 90 percent of the houses are made of mud which is not resilient to ood. The social vulnerable groups based on gender and age constitute of more than 60 percent. The estimated female population is 49 percent. Less than 10 years age group and above 50 years age group people are 12 and 9 percent, respectively. This situation has further increased the vulnerability of the exposed communities to ood. The high vulnerabilities of exposed communities have further heightened the ood risk. The number of affected population is directly linked to the spatial extent of ood. As the spatial extent and depth of ood is increasing downstream in the same manner affected population is increasing. Jhang is most affected district followed by Ha zabad.
Structural measures are highly needed in the entire lower Chenab Basin. Similarly, inundation canals will rechange the ground water level and reduce the ood rsik.
Analysis further revealed that infrastructure was badly affected by 2014-ood in the entire study region. It has undercut foundation of the non-resilient buildings and damaged hundreds of buildings in the entire region. The irrigation canals were breached by high discharge as well as roads and irrigation channels. More than 95percent of the affected villages are located on both sides of Chenab River where majority of the people are living in nonresilient mud or mud-break (Kacha) houses. The exposed and non-resilient houses were completly damaged by ood. Spatially, these houses are located in ood zone. Still the risk of potential damages is prevailing because the affected population has built their houses again over the same location. The spatial extent and depth of the ood are main characters in the destruction of houses and standing crops. The damages were maximum in Ha zabad, Chinot and Jhang with estimated economic loss of 271.8, 315 and 343 mPKR, respectively. The spatial extent, depth and magnitude of ood were variable from Head Marala to Head Trimmu in the study region. The extent and depth is increasing from north to south. Similarly, the extent of damages to human life, houses, agriculture sector is increasing towards south. Ha zabad, Chinot and Jhang are the most affected districts in the south of the study region. Agriculture and housing are the most affected sectors because the amin economic activitiy of the local residents is agricultural activitiy due to the availability of fertilte land and water. The houses are made of nonresilient material in the ood zone and esily get damaged by ood.
Analysis further revealed that the ood forecasting and zonation of ood risk zones using probabilistic and spatial hydrological approaches will identify the exposed, susceptible and vulnerable communities ). Riverine oods often burst the river banks and take away huge farmland and damage vulnerable houses and structures. However, deposition of silt and clay which may increase crop fertility but the deposition of sand completely destroys farmland. The Chenab ood plain is formed by the sediment yield deposited by the river. But ood has damaged the crop land by depositing sand on the land. On average, about 2.8feet thick layer of sand was observed over the farmland in Ha zabad and more than 3.5feet in the Chinot and Jhang. The recovering of fertile land from such sand needs time and nancial resources. GIS and Remote Sensing are the effective geospatial tools for analysis and management.
In short, exposure and vulnerability to oods is very high because population clusters are located in high-risk areas, where the individuals, households and community vulnerabilities are high. Similarly, construction in ood zone, low literacy level, high poverty, lack of social cohesion, and awareness further growing vulnerability of the exposed communities lead to high risk. Forecasting the magnitude of 100years, 125years and 150years extreme rainfall events, surface runoff and oods, delineation of high risk zone, identi cation communities and structures exposed to potential damages are important non-structural measures to reduce ood risk. Similarly, high resolution Digital Elevation Model (DEM) will help to identify suitable locations for inundation canals. These canals will not only reduce the ood risk but also recharge the groundwater level.

Conclusions
It is concluded from the analysis that ood is one of the recurrent hydrological hazards in Chenab Basin. The 2014-ood was generated by extraordinary late Monsoon activity over the upper catchment areas of Chenab Basin having intensity of 16mm/day during wet spell which is much higher than the daily average (2.8mm per day) of the past 40 years normal for the September. Flash ood dominates the upper reches while in the lower reaches riverine ooding is common. The spatial extent, depth and damages of 2014-ood the lower Chanab Basin forms two distinct zones. The ood overtopped the banks and caused damages to fully grown standing crops, infrastructure, sources of livelihood and human life losses. Based on spatial extent the study region is delineated into upper and lower zone. The upper zone comprised of districts of Gujrat, Gujranwala, Sialkot, Mandi Bahaudin and Sarghodha where the average spatial extent of ood is 0.92Km with average depth is 1.2m and estimated economic loss is approximately 92mPKR. The lower zone comprised of districts of Ha zabad, Chinot and Jhang where the average spatial extent of ood is 3.4Km with average depth is 2.8m and estimated economic loss is over 300mPKR. Greater the spatial extent and more depth leads to more damages.
It is also concluded from the analysis that heavy and prolong rainfall in summer is a major factor responsible for the genesis of ood disaster. In addition to this, excessive melting of snow and glacier, cloud bursting and deposition of silt, clay and sand in river channels are the major physical factors responsible for generation of oods. The spatial extent of aggressive weather events have also been grown during the last two decades. The signi cant increase in extream rainfall events and excessive melting of snow caps and glaciers in the headwater region, anthropogenic activities on the active ood plain and breaching of embankments have further increased the risk ood and potential damages.
There are some human ood intensifying factors including human encroachments onto the active flood plain, bursting of temporary dams behind the bridges, clearing of forests for infrastructure development, increasing exposure of impermeable soil are some of the key anthropogenic factors. These factors have also grown the extent of damages. Therefore, there is a need of policy response for the land use regulation to check encroachments onto the channel and watershed management as a ood abatement measure to reduce the risk of future mega ood events. The analysis further indicates that there is a constant uctuation in both the rainfall and river runoff, which is a clear signal of climate change.
Flood risk reduction plan based on hydro-meteorological conditions, geo-morphometric characteristics, hydrological reactions of the basin to rainfall event and community perception is highly recommended. The installation of sensor based hydro-gauging stations, automatic weather stations and Doppler weathers radar for effective ood forecasting and early warning system is also the need of such basin located in the Monsoon regime. Similarly, geo-spatial assessment of ood risk using high resolution spatial data is needed for ood risk zonation and as strategy for ood risk reduction. Disaster preparedness and resilience activities speci c to ood risk zones are also suggested as ood risk reduction strategies. Increasing retention capability of the basin by plantation in the upper catchment area is needed on emergency basis. Similarly, check dams are also important ood risk eduction strategy in upper reaches. Identi cation of suitable site for construction multi-purpose barrage and inundation canals are utmost important. This will not only reduce the risk of ood but also recharge the groundwater.

Declarations Authors Contributions
Mahmood, S and Rani, R has contributed equally in this research work.

No funding Competing Interests
No competing interest Availability of data and materials Data is available in the manuscript in the form of maps, tables and graphs. The data will also be made available on request.

Figure 1
Location of the study area and sample sites