In exercise of the powers conferred by sub section 1, read with clause b of sub section 2 of section 54 of the Dam Safety Act

EXTRAORDINARY PART III—Section 4 PUBLISHED BY AUTHORITY No. 9 96] NEW DELHI, TUESDAY , DECEMBER 17, 2024 /AGRAHAYAN 26, 194 6 CG-DL-E-17122024-259484 (m/s) Tier 1 - • • • • • • • • Tier 2 - 10 THE GAZ ETTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] Tier 3 - (2) (3) 14 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] = 1200/40*0.386 = 11.5 महीने (4) (5) )6) 16 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] (8) (m/s) 18 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] (9) 20 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] उपयोग IIC 10- 70 H3 – H6 (11) 22 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] (12) 24 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] 26 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] 28 THE GAZE TTE OF INDIA : EXTRAORDINARY [PART III—SEC.4] NATIONAL DAM SAFETY AUTHORITY NOTIFICATION New Delhi, the 5th December , 2024 F. No. TE -32/2/2023 -NDSA -MOWR .—In exercise of the powers conferred by sub -section (1), read with clause ( b) of sub -section (2) of section 54 of the Dam Safety Act, 2021 (41 of 2021), the National Dam Safety Authority, on the recommendations of the National Committee on Dam Safety, hereby makes the following regulations, namely: - 1. Short title and c ommencement . – (1) This regulation may be called the Vulnerability and Hazard Classifications of Dams Regulations, 2024. (2) This shall come into force on the date of its publication in the Official Gazette. 2. Definitions. - (1) In this regulation , unless the context otherwise requires, - (a) “Act” means the Dam Safety Act, 2021(41 of 2021); (b) “Authority” means the National Dam Safety Authority established under section 8 of the Act; (c) “hazard” means a dangerous condition or event, that threat or have the potential for causing injury to life or damage to the property or the environment ; (d) “ hazard potential” means the downstream damage that may result if the dam were to fail ; (e) “risk” means a measure of the likelihood and severity of adverse consequence, which is estimated by the mathematical expectations of the consequence of an adverse event occurring i.e. the product of the probability of occurrence and consequence; (f) “section” means a section of the Act. (g) “vulnerability” means the relative risk associated with the dams, on the basis of their condition, location and damage ; (2) Words and expressions used herein and not defined in these regulations but defined in the Act , shall have the meanings respectively , assigned to them in the Act. 3. Criteria for vulnerability and hazard classification of a dam - (1) The State Dam Safety Organization shall classify each dam under their jurisdiction as per the following, namely: - (i) Category -I: Deficiencies in dams which, if left unattended, may lead to failure. (ii) Category -II: Major deficiencies requiring prompt remedial me asures. (iii) Category -III: None or minor deficiencies which are rectifiable. (2) The v ulnerability classification shall be carried out in accordance with sub-para (c) of Part 2 of Schedule -I of the Inspection, Instrumentation, Seismic Data, Risk Assessment and Evaluation of Specified Dam Regulation, 2024 . (3) The c riteria of hazard classification shall be as following, namely: - (i) Dam hazard classification shall be based on an “additive weighting” and “point index ” and aggregates the assessment of the consequences in four major categories that is the capital value of the project, potential for loss of life, the potential for property damage and Potential for Environmental and Cultural impact. (ii) hazard potential is categorized into four classes as specified in the Table-1 below based on the consequences category: Table 1 - Consequences Categories in the Dam Classification Hazard Potential Class Consequences Categories Capital Value of Project Potential for Loss of Life Potential for Property Damage Potential for Environmental and Cultural Impact Class I Low None. Occasional or no incremental population at risk, no potential loss of life is expected. No inhabited structures. Minimal. Limited economic and agricultural development. None Class II Average Minimal or low population at risk. No potential loss of life is expected even during the worst - case scenario of emergency management . Notable agriculture or economic activities. States h ighways and rail lines. Minimal incremental damage. Short -Term or reversible impact (less than 2 years) . Class III Significant Considerable. Several inhabited developments. Potential for loss of life highly dependent of the adequacy of warning and rescue operations. Significant industry, commercial and economic developments. National and state highways and rail lines. Limited. Impact have a mid-term d uration (less than 10 years) with high probability of total recovery after mitigation measures . Class IV Critical Extreme. High density populated areas. Potential for loss of life is too high even during the best scenario of emergency management . Highly developed area in terms of industry, property, transportation and lifeline features . Severe. Long -term impact/effects in the protected areas or cultural heritage sites with low probability of recovery. 4. Failure Scenario for the Dam Hazard Classification - (1) The hazard potential classification assigned to a dam is based on consideration of the effects of failure or mis -operation during both normal and flood flow conditions. (2) The classification assigned sh all be based on the worst -case scenario of failure or m is-operation of the dam, i.e., the assigned classification sh all be based on incremental failure consequences that will result in the assignment of the highest hazard potential classification of all probable failure and mis operation scenarios. (3) Each e lement of a project shall be evaluated to determine the proper hazard potential classification for the project. (4) O nly one hazard potential classification shall be assigned to the entire project and i ndividual elements are not assigned separate classific ations. 5. Vulnerability or severity assessment . – (1) The degree of hazard shall vary with the severity of flooding and is affected by the flood and its hydraulic behaviour (extent, depth, velocity, duration and rate of rising of the floodwaters), the topography, population at risk and emergency management. (2) Once the flood hazard of the dam event (failure scenarios) has been quantified, the potential of the flood flows to cause damage or danger shall be indexed against vulnerability curves linked to meaningful hazard thresholds. (3) The vulnerability of the d ownstream community and its assets shall be described by using thresholds related to the stability of people as they walk or drive through flood waters, or shelter in a building during a flood. (4) The vulnerability to hazard shall also be influenced by the primary consideration of strategic land -use planning, which is aimed at ensuring land use is compatible with the flood risk or assessing development proposals or emergency management planning, which is aimed at addressing residual flood risks. (5) A flood severity assessment conducted as part of a dam hazard classification process shall provide information to identify those consequences with the highest significance among the entire floodplain. (6) A combined set of hazard curves (vulnerabilit y of people, vehicles and buildings) are given at Table 2 and Figure 1 below: - Table 2 - Vulnerability thresholds classification limits a Hazard Vulnerability Classification Description Classification Limit (Depth * Velocity) Limiting Water Depth (m) Limiting Velocity (m/s) H1 Generally safe for vehicles, people and buildings. D*V < 0.3 0.3 2.0 H2 Unsafe for small vehicles. D*V < 0.6 0.5 2.0 H3 Unsafe for vehicles, children and the elderly. D*V < 0.6 1.2 2.0 H4 Unsafe for vehicles and people. D*V < 1.0 2.0 2.0 H5 Unsafe for vehicles and people. All buildings are vulnerable to structural damage. Some less robust buildings subject to failure. D*V < 4.0 4.0 4.0 H6 Unsafe for vehicles and people. All building types considered vulnerable to failure. D*V > 4.0 - - a Combined Hazard – Vulnerability Classification (Smith et al., 2014) Figure 1 - Flood Hazard Vulnerability Curves (Smith et al. 2014) 6. Limits of the Study Area . – (1) In order to establish the limits of the study area for a consequences assessment the following aspects shall be considered and verified in the dam break analysis, which may help to delimit the boundaries of the model . - (a) no downstream presence of dwellings, services and other infrastructures ; (b) no future developments are expected downstream of the boundaries of the model ; (c) full attenuation of the breach outflow hydrograph along the main river ; (d) channel -conveyance capacity of the mainstream (within the riverbanks) receiving the total outflow in the downstream end of the model ; (e) The existence of a downstream dam having a reservoir that lies within the downstream limits of the hydraulic model of the upstream dam, which is either able or unable to absorb the total outflow hydrograph due to the dam breach upstream and in case the reservoir located downstream is not able to absorb the entire volume received from the upstream dam’s breach flood, a cascade failure effect sh all be scrutinized and i f a high likelih ood of failure is corroborated for the downstream dam the downstream limits shall be extended ; (2) The i nvestigation of the impact of failure or mis -operation of a dam on downstream human life, property damage, lifeline disruption, and environmental concer ns shall be sufficient to determine the appropriate hazard potential classification : Provided that if failure or mis -operation of a dam leads to the failure of a downstream dam , the hazard potential classification of the dam sh all be at least as high as the classification of the downstream dam and sh all consider the adverse incremental conse quences of the domino failures. 7. Data requirement s. – (1) The a ssessment of consequences requires information on the effects of a potential dam break, to provide the basis for the level as considered appropriate which includes data on dam and reservoir, topography , flood characteristics and inundation maps, information about the community residing in the downstream area, implications for service and business, and implications to objects of strategic or national importance. (2) Dam and reservoir data shall include information on dam type, dimensions of the dam such as height, width, and length, spillway characteristics including gates and secondary spillways, relationship showing the reservoir elevation versus storage volume, together with spillway discharge capacity up to the dam crest and comments on design, foundations and unusual conditions as well as available repor ts on the design, construction, and management of the dam and information on past incidents . (3) (i) Topographic data shall cover the river sections where the depth and velocities of the flow may cause harm to life or damage the property and the information sh all indicate the shape and slope of the valley and, when possible, the structures or surfaces influencing on the downstream flow (e.g., culverts, weirs, bridges, levees, embankments, temporary storage, floodplains, vegetation and other objec ts affecting the water surface elevations) ; (ii) Topographic data shall also determine the boundary limits of the hydraulic model of the dam break analysis which is enough to represent the entire downstream consequences and shall also include the location of major downstream tributaries that may cause concurrent flooding ; (iii) Channel cross -sections sh all be taken at regular intervals along the flood channel and a dditional sections may be obtained for areas with a change in the channel profile such as restriction in section profile, like a bridge, confluence of tributaries to the main channel and places with a significant change in the grade or cross -section of the channel ; (iv) For the dam classification process, the level of detail s of the to pography or corresponding digital elevation model (DEM) sh all be consistent, as a minimum, to a tier -I assessment. (4) Information on flood characteristics and inundation maps shall include details about historical flood levels and flood studies based on hydrographic data, as well as results from rainfall run -off modelling pertaining to different return periods which also contain results of dam -break flooding under overtopping and non -overtopping conditions and shall include travel times of flood waves to downstream locations of habitations . (5) Information about the community residing in the downstream area shall include .- (i) location, size and type of areas with human settlements within the possible area of inundation, the vulnerability of various elements of the downstream community and the warning time available ; (ii) details about awareness and flood preparedness of the downstream community and their temporal variation pattern concerning days of the week and months and seasons ; (iii) description of the areas identified for future development along with the land use classes and areas with toxic substances, and the information on the infrastructure that may be affected (e.g., transport, power lines, water supply and sewerage lines, gas pipes etc.). (6) Implications of the dam break consequences for service and business shall include the importance of the water storage to the business (e.g., municipal water supply, irrigation or hydropower generation), financial overburden , to meet the costs of failure and the value of water in the storage reservoir. (7) Implications to objects of strategic or national importance include inundations of areas which shall have consequences of national significance like an inundation of a nuclear power plan t or a thermal power plant, or places which if inundated will pose a threat to the national security , and may also include important historical structures or biodiversity reserves or both. 8. Tiered assessment of Inundated Area and Flood Water Levels. - (1) With due considerations of the time requirement and cost of detailed studies required to delineate areas which shall be inundated by a dam breach f lood, tiered approach shall be taken to produce dam-breach inundation zone maps. (2) The level of analysis for the tiered approach shall correlate with the sophistication and accuracy of the analys is with the scale and complexity of the dam and downstream area under investigation, as per Table 3 . (3) For Dam Hazard Classification process , a Tier -I analysis as specified in Table 3 shall be considered and adopted in the following cases, namely: - (a) dams which, due to their particular location and own characteristics, m ay be directly inferred as “low hazard” and a Tier - I analysis sh all confirm the “low hazard” hypothesis ; (b) as the first estimation for any high hazard dam under analysis and i f the results obtained through a Tier-I analysis are enough to classify the specified dam under the highest hazard class, no further refinement would be required in the classification process ; (c) for any specified dam, irrespective of its “hazard”, only if the results from a Tier -I analysis ar e reliable enough to conclude that further refinements shall not introduce changes in the hazard classification. (4) A higher level of complexity in the consequence’s estimation (i.e. Tier – II and III) shall be introduced for the classification process i n the following cases , namely: - (a) consequences index (scoring points) obtained through a Tier -I analysis set the Hazard Class near the boundary or threshold of a higher or lower hazard category ; (b) better estimate in the population at risk assessment shall be ensured since it is considered as the critical indicator in the hazard classification process of the specified dam ; (c) clearer estimates in the flood severity assessment are desired for the consequences’ evaluation, which shall make the use of a two -dimensional model . 9. Estimating population at risk. – (1) The population at risk shall include persons directly exposed to flood waters if they are not evacuated , and a fter the delineation of the area inundated due to dam breach, estimation of the population at risk may be carried out. (2) It sh all be estimated using demographic data with occupancy rates for residences, number of students at schools, number of persons in industrial, hospital, commercial and retail areas. (3) The population at risk estimates may vary according to the time of day, the day of the week and month or season and it is necessary to prepare more than one estimate and select the highest of these for determination of the consequence category of the dam. (4) It is important to consider the visitors to the recreational sports, camps, concert halls, parks and gardens as also those who are driving through the roads or taking a railroad journey which gets inundated due to a dam break flood. (5) The incremental analysis shall be taken into consideration for the estimation of population at risk and the rest of the consequen ces. 10. Assessing potential damages and losses . – (1) The potential damages and losses due to a dam break may be grouped into classes, including consequences of similar nature for the purpose of risk assessment which includes total infrastructure costs, losses accrued due to the dam not being able to serve the purposes it is meant to, health and social impacts, and the environmental impacts. (2) Damages and losses may be classified as direct or indirect and d irect damages and losses comprise , those losses , which result from contact with the floodwaters and i ndirect damages and losses encompass all other damages and losses. (3) The severity of each of these damages and losses may be either minor, medium, major or catastrophic which may be established for each group of damage or loss, and summarised to the overall level of severity, with due consideration to the regional or national economic perspective. 11. Assessment of health and social impacts . – The assessment of health and social impact shall be assessed on the following parameters , namely : - (a) the effects of dam break on health and social affairs shall depend on the nature, location, and extent of the area affected by the dam failure, with regards to the distribution of the human habita tion; (b) consumption of polluted drinking wate r or food due to contamination of the source or supply network which may be due to failure or shortage of water, sewage, power supplies and u ncontrolled release of sewage, industrial or toxic waste as a result of a dam break which may lead to widespread contamination ; (c) social impacts of dam break shall depend on demographic characteristics, social and community values, needs and networks, the extent of community support services, the capacity of respondin g institutions as well as the degree of disaster preparedness and warning time available. 12. Consideration of Future Developments. - The consequence classification for a dam shall reflect the current downstream development as well as the future developmen t plans. Table 3 - Tiered approach to dam breach inundation mapping Tier Level Applications Topography /Bathymetry Breach Parameter Prediction Handling of the Dam Breach Parameters’ Uncertainty Peak Breach Discharge Prediction Downstream Routing of Breach Outflow Hydrograph Downstream Risk Evaluation Tier 1 – Basic level screening and simple analysis • Hazard Classification Process • First level screening for significant or high hazard dams • Low hazard potential dams Low resolution terrain data (e.g., SRTM, ASTER, or ALOS), with maximum 30 m resolution. No bathymetry required Empirical formulae • Engineering Judgmen t • Reasonableness of the peak breach discharge and velocities Empirical formulae if inflow design flood hydrograph is not available, otherwise unsteady flow routing through modelled reach HEC -RAS, MIKE or similar one dimensional (1D) or two dimensional (2D) unsteady flow numerical models Peak discharge, water surface elevation, depth*velocity and flood wave travel time Tier 2 – Intermediate level of analysis • Large significant hazard dams • All high hazard dams Medium resolution terrain data (e.g., 10 - 15 m resolution, CartoDEM1) and elevations adjusted through ground control points (GCPs). Bathymetry required Empirical formulae • Reasonableness of the peak breach discharge • Sensitivity analysis Unsteady flow routing through modelled breach HEC -RAS, MIKE or similar two dimensional (2D) unsteady flow numerical models considering the bathymetry Peak discharge, water surface elevation, depth*velocity, flood wave travel time, and approximate PAR assessment Tier 3 – Advanced level of analysis • Significant hazard dams with complex downstream flooding • High hazard dams with large population at risk (PAR) High resolution terrain data (Lidar, ALSO enhanced) minimum 5 m resolution. Ground control points (GCPs) required. Bathymetry required Empirical equations, physically based models (one or two dimensional) • Probabilistic Analysis (Monte Carlo simulations or similar methods) Unsteady flow routing through modelled breach Coupled one -two dimensional (1D - 2D) unsteady flow numerical model. Bathymetry also considered Peak discharge, water surface elevation, depth*velocity, flood wave travel time, and detailed PAR assessment 13. Hazard Classification for dams. – (1) Hazard classification aggregates the assessment of the consequences in following major categories, namely: - (a) the capital value of project shall include the capital value of the project’s elements which may be destroyed or damaged, and the loss of benefits, services, revenues provided by the dam project. (b) the potential for loss of life be estimated indirectly through the estimation of the total population at risk in the downstream areas and this category shall also consider the severity of the breach or failure flood if the quality or type of modelling meets some standards, and the approximate arrival time of the flood wave (to the closest and affected populated area), which is an indirect measur e of the available warning time; (c) the p otential for property damage shall include the amount of damage to residential and commercial property, agricultural lands, transportation facilities such as roads and bridges, damage and disruption of lifeline and community service facilities ; (d) the potential for enviro nmental and cultural impact shall i nclude the amount of damage to protected areas in the country (wildlife sanctuaries, forest reserves, etc.) as well as potential impact to infrastructures of cultural heritage or national importance. (2) The detailed desc ription s of all categories for each of the four hazard classes are specified in Table 4. (3) ( a) the additive weighting or point index scheme employs numerical ratings of the consequences which reflect the relative importance of each consequence and the range of severity of the impacts ; (b) the summation of the rating points from each consequence shall be used to establish the characteristics of the consequences of failure of a given dam ; (c) the overall categories and indicators used in the hazard potential classification for dams are specified in Table 5. Table 4: Dam Classification based on the Additive weighting Scheme (Potential Consequences Index) Hazard Potential Class Potential Conseque nces Index (PCI)* Consequences Categories Capital Value of Project Potential for Loss of Life Potential for Property Damage Potential for Environmental and Cultural Impact Class I < 300 Low None. Occasional or no incremental population at risk, no potential loss of life is expected. No inhabited structures. Minimal. Limited economic and agricultural development. None Class II < 300 Average Minimal or low population at risk. No potential loss of life is expected even during the worst -case scenario of emergency management Notable agricult ure or economic activities. States highways and/or rail lines. Minimal incremental damage. Short -Term or reversible impact (less than 2 years) Class III 300 < P CI < 600 Significant Considerable. several inhabited developments. Potential for loss of life highly dependent of the adequacy of warning and rescue operations. Significant industry, commercial and economic developments. National and state highways and rail lines. Limited. Impact have a mid-term d uration (less than 10 years) with high probability of total recovery after mitigation measures Class IV > 600 Critical Extreme. High density populated areas. Potential for loss of life is too high even during the best scenario of emergency management Highly developed area in terms of industry, property, transportation and lifeline features Severe. long -term impact/effects in the protected areas or cultural heritage sites with low probability of recovery. * Disclaimer: Dams with total consequences index near the boundaries between two classes (+/ - 50 points) warrant a comprehensive assessment and additional engineering judgment to determine t he actual hazard classification Table 5 - Numerical Rating Points a nd Categories for Assessing Consequences Consequences Category Indicator Parameter Consequences Rating Points (min - max) Considerations Capital Value of Project Dam Height 20 -100 Revenue Generation or Value of Reservoir Content depending upon the reservoir purpose (water supply, irrigation, hydropower, etc.) Project Benefits 0-300 Potential for Loss of Life Population at Risk 20-600 Incremental Population at Risk under higher flood severity areas. Minimum arrival of the breach/flood wave to the nearest populated area downstream of the dam Critical Arrival Time 0- 100 Potential for Property Damage Infrastructures Damaged 0- 330 Residential and Commercial Properties Roads, Bridges, Transportation Facilities Lifeline Facilities and Community Services Services Disrupted 0-185 Potential for Environmental impact Environmental Impact 0 - 200 Protected Areas and Cultural infrastructures of National importance under higher flood severity areas Cultural Heritage 0 - 140 (a) Capital Value of Project (1) It shall include the capital value of the project’s elements which shall be destroyed or damaged, and the loss of benefits, services, revenues provided by the dam project . (2) The two parameters namely: - Dam Height Index and Project Benefits Index shall be used for assessment of capital value of project ,- A. Dam height index (i) Dam height may be considered as indicative of the capital value of a dam. (ii) Consequence rating points corresponding to dam height index shall be calculated by the utility curve as specified in Figure 2. Figure 2 - Consequences Rating Points for Dam Height Index (I DH) Alternatively, the index can be computed numerically according to the following formula: 𝑰𝑫𝑯 { 𝟐𝟎,(𝒇𝒐𝒓 𝒉≤𝟓) 𝟏𝟓.𝟕+ 𝟏.𝟏𝟐∗[𝑳𝑵(𝒉)]𝟐.𝟖𝟐𝟗𝟐,(𝒇𝒐𝒓 𝟓<ℎ<𝟏𝟎𝟎) (1) 𝟏𝟎𝟎 ,(𝒇𝒐𝒓 𝒉 ≥𝟏𝟎𝟎) Where ,- IDH : Dam height index points, and h : is the height of the dam in meters B. Project benefits index. - (i) Project benefits index (I PB) shall be estimated us ing the following subcategories , namely :- reservoir content or water supply index (I RES), irrigation index (I I), hydropower generation index (I HP), and industrial use index (I IU), and accordingly the total project benefits index can be calculated as follows: IPB=IRES+II+IHP+IIU (2) (ii) in case the cascade failure effect in a dam series is ascertained, the rating points sh all consider all the affected dams in the system, regardless of the potential dams’ ownership conflicts or administrative jurisdiction differences. (iii) the following procedure shall be followed to estimate the rating points for each of the sub - categories : - (I) Reservoir contents or water supply index(𝐈𝐑𝐄𝐒): The value of the reservoir contents shall be calculated as a function of the time that it w ould take to fill the reservoir and t he time is computed in months, by dividing the reservoir volume in million cubic metre ( Mm3) by the average river flow in m3/s (average of daily means, not daily peaks), and converting the resulting number into months by multiplying it by 0. 386. Example; - If there is a reservoir with volume of 1200 Mm3, and an average flow of 40 m3/s, the time to fill the reservoir with the average river flow shall then be: TF=VQ⁄∗0.386 (3) Where, TF = Time to fill the reservoir in months V = Volume of the reservoir in Mm3 Q = Average river flow in m3/s 020406080100120 1 10 100Points (IDH) Dam Height (m) Applying the equation to the values in the example, we get TF= 1200/40*0.386 = 11.5 months The time to fill is entered into Figure 3 , and for the 11.4 months, shall be read as 23.7 points , and a n alternative way to compute the number of points is by using the following formula ; namely; - IRES{5024⁄∗TF ,(for TF<24) 100 ,(for TF≥24) (4) Where, IRES = Reservoir Content or water supply Index Figure 3 - Consequences Rating Points for Reservoir Content Index (I RES) (II) Irrigation land index(𝐈𝐈): Consequences rating points for irrigated land index shall be calculated as specified in Figure 4 . The number of points for irrigated land is also computed as: II{area ,(for area <100) 100 ,(for area ≥100) (5) Where, 𝒂𝒓𝒆𝒂 = irrigated area in 1,000 ha. 𝑰𝑰 = irrigated land index (III) Hydropower generation index(𝐈𝐇𝐏): Consequences rating points for hydropower generation index shall be calculated as specified in Figure 5. The hydropower generation index can also be computed by: IHP{P10⁄ ,(for P <1000) 100 ,(for P ≥1000) (6) Where, P = installed capacity in MW. IHP = Hydropower index Figure 4 - Consequences Rating Points for Irrigated Land Index (I I) Figure 5 - Consequences Rating Points for Hydropower Generation Index (I HP) (IV) Industrial use index (𝐈𝐈𝐔): The corresponding rating points shall be calculated using the same methodology as explained for waters supply index and specified in Figure 3 and equation (3). (b) Potential for loss of life . – (1) The potential for loss of life shall be estimated indirectly through the estimation of the total population at risk in the downstream areas and this category shall consider the severity of the breach or failure flood, and the approximate arrival time of the flood wave, which shall be an indi rect measure of the available warning time. (2) In this category, as in the project benefits index (I PB), the evaluation of failure consequences of a dam in a cascade system shall include the failure consequences of dams located downstream if such failure be caused by the dam under scrutiny and if that failure shall not otherwise have occurred in the scenario under study. (3) The rating points sh all consider the consequences of all dams involved, regardless of the potential dams’ ownership conflicts or administrative jurisdiction differences. (4) In cases where the failure of the downstream dam is ascertained, the highest hazard category m ay be adopted without the need for further justifications. A. Incremental population at risk index (IPAR). – (i) An envelope curve for estimating the potential loss of life (PLL) when there is great er than five minutes of warning, but less than ninety minutes, may be expressed as a function of the population at risk (PAR) as PLL = PAR0.6 (7) Equation ( 7) has been used to establish the general shape of the utility curve for the PAR ( Figure 6 ). Equation (8) below can also be used for numerical calculation IPAR{20∗PAR0.2954,(for PAR<100,000) 600 ,(for PAR ≥100,000) (8) Where, PAR = incremental population at risk (ii) As the equation (8) specifie s, the incremental population at risk sh all be used in this approach by subtracting from the consequences of the dam failure , the ones that would have happened by the natural flow anyway, that is, even if the dam had not failed , provided , for a sunny -day failure scenario (normal operation), incr emental and total consequences are to be considered equal. Table 6 - Highest Severity Categories1 used to estimate Population at Ris Hazard Vulnerability Classification1 Description Classification Limit (Depth * Velocity) Limiting Water Depth (m) Limiting Velocity (m/s) H3 Unsafe for children, elderly and vehicles D*V <0.6 1.2 2.0 H4 Unsafe for vehicles and people. D*V < 1.0 2.0 2.0 H5 Unsafe for vehicles and people. All buildings vulnerable to structural damage. Some less robust buildings subject to failure. D*V < 4.0 4.0 4.0 Table 6 - Highest Severity Categories1 used to estimate Population at Risk H6 Unsafe for vehicles and people. All building types considered vulnerable to failure. D*V > 4.0 - - Notes: 1Complete Categories are shown in Figure 1 and Table 2 Figure 6 - Consequences Rating Points for Incremental Population at Risk (I PAR) (iii) The population at risk shall be estimated using the vulnerability approach specified in regulation 5. Only the population exposed to the highest hydraulic conditions (classes H3 to H 6, Table 6), shall be considered as at risk, and shall be counted in the index calculation and t o obtain a full advantage or benefit of the flood severity analysis, the use of a two -dimensional depth -averaged (2DH) hydraulic model is recommended. (iv) The adequacy of warning to the downstream population has not been considered for the index estimation of this category. (v) The population at risk estimation and index sh all reflect the current downstream development and the future development plans, especially for dams in planning or under construction stage. B. Critical arrival time index (IAT): The factors or conditions to be considered for critical arrival time index shall include the following, namely: - (i) the effectiveness of the warning and evacuation process ; (ii) successful evacuation depend s on the time available until the arrival of the floodwater in an area and the time required for evacuation and the following t wo elements determine the time available for evacuation: (a) The time available between the first s igns and the initiation of the flood, i.e. the breach ; and (b) The time available between the breach initiation and the arrival of the floodwaters at a certain location (called arrival time). (iii) the time lag between first signs and the in itiation of a flood depends on the (threatening) types of flood and the availability of warning systems. The “critical” arrival time calculation is recommended , understanding as “critical” the minimum wave arrival time computed in the nearest populated area downstream the dam (i.e. town, city, village). This value can be easily obtained after the dam break analysis study is carried out ; (iv) Researches by the U nited States Bureau of Reclamation (Graham, 1999) on the field of the potential loss of life, found that with 90 minutes or more of warning time the toll of victims was considerably lower even in cases where thousands had to be evacuated ; (v) The utility curve for the arri val time index was developed (Figure 7) assigning the highest rating points (100 points) to those cases with less than ninety minutes between the breach initiation process and the moment the nearest population start to be inundated. After ninety minutes, the rating or penalty points are exponentially reduced until a minimum of zero points, when a minimum of 12 hours of arrival time is computed ; (vi) If a numerical estimation of the critical arrival index is preferred, equation (9) below may be used 𝑰𝑨𝑻 { 𝟏𝟎𝟎,(𝒇𝒐𝒓 𝑨𝑻≤𝟏.𝟓 𝐡𝐫𝐬) 𝟏𝟒𝟑.𝟐𝟖∗(𝟎.𝟕𝟖𝟔𝟖)𝑨𝑻,(𝒇𝒐𝒓 𝟏.𝟓<𝐴𝑇<48) 𝟎,(𝒇𝒐𝒓 𝑨𝑻≥𝟒𝟖 𝐡𝐫𝐬)(9) Where, 𝑨𝑻 = critical arrival time in hours 𝑰𝑨𝑻 = critical arrival time index Figure 7 - Consequences Rating Points for Critical Arrival Time Index (I AT) (c) Potential for property damage . – (1) Property damage category shall include damage to inhabited dwellings, commercial and industrial developments, agricultural lands and crops, roads, highways and utilities and the associated economic losses both permanent and temporary and shall include damages to lifeline facilities and economic disruption. (2) The indexes specified in this category, are meant to identify the relative magnitude of losses against a broad scale of values and n o attempt shall be made to assess actual market value or actual Indian rupees losses. A total of ten sub-indexes were developed to estimate the potential damage to properties is specified in Table 7. (3) The range of consequences rating points listed in Table 7 reflect both the importance of a facility and the relative magnitude of expected dam ages based on the hydraulic conditions of the flood (severity). The final value for each index shall be selected within the range depending upon the flood severity class obtained from the inundation maps results and the total area affected. Table 7 specifi es the general guidance in the severity classes to be considered in each case. If any item is located out of those classes, the final index should be considered as zero. (4) Utility curves serve as a guide in the calculation of rating points of each type of property. A larger or smaller value may be selected depending on the need for conservatism in protecting the facility or area that could be damaged. Practical illustration in how to use the utility curves is specified in Schedule A. (5) The final property dama ge index is given by the sum of all the rating points as follows: 𝑰𝑷𝑫=𝑰𝑵𝑯+𝑰𝑺𝑯+𝑰𝑹+𝑰𝑰𝑪+𝑰𝑨𝑨+𝑰𝑹𝑨𝑹+𝑰𝑹𝑨𝑼+𝑰𝑾𝑺+𝑰𝑬𝑹+𝑰𝑬𝑷 (10) Where, 𝑰𝑷𝑫 = Property Damage Index. 𝑰𝑵𝑯 = National Highways index 𝑰𝑺𝑯 = State Highways index 𝑰𝑹 = Railroads index 𝑰𝑰𝑪 = Industrial and Commercial use Index 𝑰𝑨𝑨 = Agricultural/Aquaculture use Index 𝑰𝑹𝑨𝑹 = Residential Areas (Rural) Index 𝑰𝑹𝑨𝑼 = Residential Areas (Urban) Index 𝑰𝑾𝑺 = Water Supply/Treatment Facilities index 𝑰𝑬𝑹 = Emergency Response Facilities index 𝑰𝑬𝑷 = Electric Power Facilities Table 7 - Consequences Indexes for Potential Property Damage Category (d) Potential for Environmental Damage (1) This component of the hazard potential assessment takes into consideration the impact over the environment and cultural heritage sites, specifically to those considered as protected areas in the country. (2) Conservation or Protected Areas are defined as areas of notable environmental or historical interest or importance which are protected by law against undesirable changes. These areas are conserved by varying levels of legal protection which are given by the policies formulated by the government of India or global conve ntions. Notes: 1 Rating points per area/length affected. If there is no item/facility affected within the severity classes zero points should be used 2 Flood Severity Categories to be considered to estimate final rating points along with relative importance of the item/fa cility and the extents of the impact (3) The proposed indexes to evaluate the impact under this category are specified in Table 8. Potential Environment and Cultural index (I ECI) can be calculated as follows: 𝑰𝑬𝑪𝑰=𝑰𝑷𝑨+𝑰𝑪𝑯 (11) Where, 𝑰𝑬𝑪𝑰 = Environmental and Cultural Index. 𝑰𝑷𝑨 = Protected Areas Index 𝑰𝑪𝑯 = Cultural Heritage Index Table 8- Consequences Indexes for Potential Environment and Cultural impact Indicator Parameter Type of Property Index Rating Points1 Flood Severity Class2 Protected Areas National Parks, Wildlife Sanctuary, Community Reserve, Conservation Reserve IPA 5 - 50 H3 – H6 Cultural Heritage World and National heritage sites (temples, monuments, caves) ICH 5 - 50 H5 – H6 Notes: 1 Rating points per item/site affected. If there is no item/site affected within the severity classes, zero points should be used 2 Severity Categories to be considered to estimate final rating points along with relative importance of the site 14. Dam Classification and the Potential Consequences Index (P CI). - (1) As part of the final step in the additive weighting scheme specified in sub -regulation (3) of regulation 13 , the final hazard potential classification shall be obtained after adding up all the index values (rating points) for each of the categories. For that purpose, equation (12) may be used: 𝑷𝑪𝑰=𝑰𝑫𝑯+𝑰𝑷𝑩+𝑰𝑷𝑨𝑹+𝑰𝑨𝑻+𝑰𝑷𝑫+𝑰𝑬𝑪𝑰 (12) Where, 𝑷𝑪𝑰 = Potential Consequences Index. 𝑰𝑫𝑯 = Dam Height index 𝑰𝑷𝑩 = Project Benefits index 𝑰𝑷𝑨𝑹 = Population at Risk Index 𝑰𝑨𝑻 = Critical Arrival time Index 𝑰𝑷𝑫 = Property Damage Index 𝑰𝑬𝑪𝑰 = Environmental and Cultural Index (2) The final hazard potential class will be a function of the total rating points, i.e. the value of the Potential Consequences Index ( PCI) and Table 4 describes the relationship of the consequence’s categories with the final hazard class . (3) Dams with total consequences index near the boundaries between two classes (+/ - 50 points) shall be comprehensively assessed and additional engineering judgment shall be used to determine the actual hazard classificatio n. ANIL JAIN , Chairman [ADVT. -III/4/Exty./ 766/2024 -25] SCHEDULE A Summary of Utility Curves for Points Score Estimation (Property Damage and Environmental/Cultural Impact) Figure C. 1 - Utility Curves for Point Score Estimation of National Highways Figure C. 2 - Utility Curves for Point Score Estimation of State Highways Figure C. 3 - Utility Curves for Point Score Estimation of Railways Figure C. 4 - Utility Curves for Point Score Estimation of Industrial & Commercial Land Use Figure C. 5 - Utility Curves for Point Score Estimation of Agricultural Land Use Figure C.6 - Utility Curves for Point Score Estimation of Built -up Urban Land Use Figure C. 7 - Utility Curves for Point Score Estimation of Built -up Rural Land Use Figure C. 8 - Utility Curves for Point Score Estimation of Water Supply/Treatment Facilities Figure C. 9 -Utility Cu rves for Point Score Estimation of Emergency Response Facilities Figure C. 10 - Utility Curves for Point Score Estimation of Electric Power Facilities Figure C. 11 - Utility Curves for Point Score Estimation of Protected Areas Figure C. 12 - Utility Curves for Point Score Estimation of Cultural Heritage Sites Uploaded by Dte. of Printing at Government of India Press, Ring Road, M ayapuri, New Delhi -110064 and Published by the Controller of Publications, Delhi -110054.