{"id":119128,"date":"2021-10-12T16:46:58","date_gmt":"2021-10-12T23:46:58","guid":{"rendered":"http:\/\/www.lankaweb.com\/news\/items\/?p=119128"},"modified":"2021-10-12T16:46:58","modified_gmt":"2021-10-12T23:46:58","slug":"save-parakrama-samudraya","status":"publish","type":"post","link":"https:\/\/www.lankaweb.com\/news\/items\/2021\/10\/12\/save-parakrama-samudraya\/","title":{"rendered":"Save Parakrama Samudraya"},"content":{"rendered":"

Bandula Kendaragama, Dam Safety Consultant, Melbourne, Australia<\/em><\/span><\/h2>\n\n\n

This\narticle is written based on information collated through consultations that\nwere recently submitted as a technical report to His Excellency Gotabhaya\nRajapaksaand other relevant government authorities. The consultations\nwere among those who had been interested in dam safety and were directly\ninvolved in managing the Narrowly-Missed\u201d breach and in the reconstruction of\nthe Parakrama Samudraya bund after the Cyclone in 1978. They considered it\nappropriate to share their concerns and acquired knowledge with the public at\nthis crucial juncture of decision-making on the safety of the aging irrigation\ninfrastructures in Sri Lanka.<\/p>\n\n\n\n

The Parakrama Samudra Reservoir was built by King Parakrama\nBahu the Great, during his reign from 1153 to 1186 AD. It has a reservoir\ncapacity of 116,000 acre-feet, feeding approximately 25,000 acres of paddy\ncultivation. This reservoir has a bund 52 feet high and 10 miles long.  <\/p>\n\n\n\n

The\nstudy on Parakrama Samudra bund was undertaken due to information and misinformation\nthat had been widely shared and debated in the formal media, and especially on\nsocial media, concerning Parakrama Samudra bund being proposed as a site to\nconstruct an 8 feet wide walking path. Furthermore, it is noted that similar walking\npaths will be constructed on bunds of other reservoirs, such as Kanthale, Udukirala\nWewa etc.,<\/p>\n\n\n\n

Cyclone\nin 1978<\/strong><\/p>\n\n\n\n

The\n1978 Cyclone started with the onset of the storm formed on 20 November 1978 over\nthe southwest Bay of Bengal.  It\nintensified gradually, reaching Super Cyclonic Storm Status Category 4 Cyclone\non 23 November with a gusty wind speed of 220 kmph. The 1978\nCyclone was the second strongest Super Cyclonic Storm to strike Sri\nLanka\u2019s Eastern Province since modern records began. The cyclone\nattained peak intensity on 23 November, before making landfall in Batticaloa.  The Eastern Province was heavily affected by\nthe cyclone.  <\/sup><\/sup><\/p>\n\n\n\n

The cyclone had devastating impacts in Sri Lanka, killing approximately 915\npeople and an unaccounted number of cattle and other animals. It is estimated\nthat more than one million people were affected, with over 250,000 buildings\ndamaged, and one-fifth of Batticaloa’s fishing fleet destroyed. Nine of the\neleven paddy stores were destroyed and 90 % of the coconut plantation (about 28,000\nacres) in the Batticaloa district were destroyed. Also, in the Polonnaruwa\nDistrict, the public and private infrastructure, paddy and rice stored in food commissioners\nand cooperatives, coconut cultivation etc., were devastated.<\/p>\n\n\n\n

Cyclone and Parakrama Samudra<\/strong><\/p>\n\n\n\n

The Cyclone reached the Parakrama\nSamudra bund at approximately 6:30 pm on 23 November and lasted until approximately\n4:00 am on 24 November. According to eyewitnesses, the height of the waves was\n10 to 12 feet. Knowing the imminent catastrophic danger of overtopping\nleading to a breach of the bund, Mr. A. D. S. Gunawardana (the Irrigation\nEngineer in charge of Polonnaruwa), Mr. Austin Fernando (the Government Agent of\nPolonnaruwa) and several other officials on duty were on standby with\nbulldozers at strategic locations (such as the sluice and spillway) to breach\nthe bund if required. <\/p>\n\n\n\n

The\nidea behind this decision was if the predicted overnight\nrainfall <\/a>occurred and the anticipated inflow to Parakrama Samudra did eventuate,\nthe inflow would have been greater than the outflow with all 10 radial gates and\nthe sluice gates kept open. There was a risk of overtopping and breaching the\nbund. Hence, an artificially introduced breach of the bund to discharge floods\nalong the existing channels would prevent a haphazard catastrophic breach at an\nunknown and unwanted location, which could inundate the heavily populated downstream\nareas. Such an emergency rapid drawdown is the standard practice to prevent a dam\nbreach. Fortunately, predicted overnight rainfall was low, however the drawdown\nof the reservoir continued overnight.<\/p>\n\n\n\n

Following\nthe overnight drawdown, about 2\/3 of the 12 feet wide bund top road and a large\nportion of the upstream shoulder were found to have slipped into the reservoir,\nleaving only about 1\/3 of the bund top road intact. There were widespread slips\nalong the full length of the bund. The damaged areas were repaired with\nearthfill and Ralapanawa was reinstated as a short-term risk reduction measure.\nThe upstream face of the Ralapanawa was not flattened to improve the safety margin\n(i.e., Factor of Safety) of the bund in case of future similar drawdowns, as it\nwas a long-term risk reduction measure to be implemented by the Government\nAuthorities.  Therefore, consideration\nshould be given to implementing appropriate long-term risk reduction measures.<\/p>\n\n\n\n

Walking\nTrack Proposal<\/strong><\/p>\n\n\n\n

Based\non the information available to date, the proposed walking path will be\nconstructed on the upstream side of the bitumen surfaced bund top road where\nthere was a sliding failure during the 1978 cyclone and floods (see figure 1).  <\/p>\n\n\n\n

\"\"\/<\/figure>\n\n\n\n

Figure <\/a>1 \u2013 Typical section of the crest of the dam or bund showing the proposed walking\npath found in the social media, presented during the webinar organised by the\nInstitute of Engineers (Sri Lanka) and shown on Sri Lankan TV.<\/p>\n\n\n\n

Several long tension cracks,\nsealed with tar, are present on the bitumen surfaced bund top road, as seen in\nvideos by Sri Lankan media. Most of them are located along (parallel to) the\nbund top road, thus increasing the risk of sliding failures similar to those that\noccurred during the 1978 floods. Additional loads due to the construction of a\nwalking path would widen and deepen those tension cracks, compromising the\nsafety of the bund, which is not known. \n<\/p>\n\n\n\n

Therefore,\nit is the considered view that additional loading on top of the 1978 sliding\nmass for construction of the walking path would increase the risk of\nreactivating the 1978 slides during a future rapid drawdown, similar to the\nincident in 1978. <\/p>\n\n\n\n

It is understood and\nappreciated that the Irrigation Department is currently undertaking\ngeotechnical investigations to assess the safety margin of the bund.<\/p>\n\n\n\n

The highest concern is dam safety<\/strong><\/p>\n\n\n\n

Based on the information available, it is understood\nthat there is a period of 741 years (i.e. from 1159 to 1900), where the\nperformance of the bund is not documented and unknown. However, it is reported\nthat the bund was totally breached during the colonial era. According to R. L.\nBrohier, the bund and the reservoir were abandoned for more than a century. <\/p>\n\n\n\n

Given\nthat the population at risk in case of a dam break is extremely high<\/strong>, it\nappears that the consequence category of this bund is Extreme\u201d<\/strong> as\nper the current international dam safety guidelines.  Therefore, the proposed walking path at\nParakrama Samudra cannot be compared to that of the Kurunegala Wewa,\nBoralesgamuwa Lake etc., constructed along the reservoir rim, and the walking\npaths constructed around water bodies in the suburbs of Colombo. <\/p>\n\n\n\n

It is understood that\nthe Parakrama Samudra is formed by combining three reservoirs of unknown\nhistory. Therefore, the bund may have been raised in several stages during the\n741 years associated with unknown performance. It is not known whether dam\nsafety-related defects of the bund, such as slips or slides, cracks, animal\nburrows, sinkholes, soft areas, root bowls, zones of desiccation cracking,\nzones of residual shear strength due to historical failures etc., were repaired\nto satisfactory standards, or not. <\/p>\n\n\n\n

The aging of dams constructed of earth and\nrockfill material is due to time-related changes in the properties of the\nmaterials of the structure and its foundation<\/a>.  As reported in a technical paper published in\nMay 2010 by the United States Society of Dams, the aging or deterioration of\nembankment dams and their foundations are of concern. These concerns extend\nthroughout the entire life of the dam until safe abandonment or demolition. <\/p>\n\n\n\n

Recent interventions on dam safety<\/strong><\/p>\n\n\n\n

Given the dam safety issues associated\nwith this <\/a>controversial walking path project, the\nWater Forum of the Institute of Engineers in Sri Lanka conducted a webinar on 9\nSeptember 2021 on Usage of\nInland Water Bodies for Recreation\u201d. More than 280\npersonnel, mainly engineers, participated in this webinar and raised over 100\nquestions related to the safety of the bund. Several questions were raised on\nfundamental errors and potential failure modes associated with the proposed walking\npath. It appears that ad hoc decisions have been taken for reasons unknown. The\nlack\nof laws and dam safety regulations in Sri Lanka could be one of the reasons for\nsuch ad hoc decisions taken by various individuals and organizations. <\/p>\n\n\n\n

As far as dam safety\nregulations are concerned, India is well ahead of Sri Lanka. Even Ghana in\nAfrica has introduced Dam Safety Regulations to ensure the safe design,\nconstruction, operation, and maintenance as well as decommissioning of dams. <\/p>\n\n\n\n

Based on statistics of\nembankment dam failures and accidents, 48% of dam failures are related to\novertopping and failures of appurtenant structures, and 46.5% are due to\ninternal erosion.  Due to the absence of\nan internal filter system in this bund, it is not only the slope instability,\nbut also the internal erosion that is likely to be a prominent potential\nfailure mode. <\/p>\n\n\n\n

It is understood that planning is underway to\nconstruct several <\/a>fast-food\noutlets and toilet facilities (including a changing room\u201d) <\/a>at the toe of the bund, i.e., within the reservation area of the bund located\nimmediately downstream of it. It is to be stressed that this stretch of land\nalong the bund is a critical area to ensure the safety of the bund<\/strong>.\nIdentification of dam safety features in this area such as heaving the ground, cracks,\nwet areas, springs, seepage locations etc., is critical.  Digging of\nlavatory pits, trenches etc., could intercept permeable layers in the\nfoundation and may trigger backward erosion tunnels\u201d leading to piping, which\nis a major failure mode in embankment dams (or, bunds). Excavations in this\narea could lead to sides of the downstream face of the bund, compromising its safety\nmargin.  <\/p>\n\n\n\n

Should there be a need to improve the safety margin\nof the bund, additional stabilizing fills are to be constructed in this area\nover the downstream face of the existing bund.  An access road along the\ndownstream toe of the bund is an essential item for repairs and routine\nmaintenance of the bund.  Given the proximity to the dam, this reservation\narea should be used to stockpile materials to be used during dam emergencies\nsuch as filter sand, crushed rock, rockfill etc., and movement of construction\nmachinery for maintenance and repairs. This area is an integral part of the\nbund and should not be used for either permanent or temporary constructions<\/strong>.\nTherefore, consideration should be given to providing these facilities at an\nalternate suitable location, perhaps close to the Government Agent\u2019s residence,\nor thereabouts.<\/p>\n\n\n\n

Recommendations\nto maintain dam safety<\/strong><\/p>\n\n\n\n

Based\non dam safety concerns and consequences discussed, it is recommended that:<\/p>\n\n\n\n

  1. the crest of\nthe bund is reserved for routine maintenance, including replacement of\ndisplaced Ralapanawa if necessary, placement of additional boulders if required,\nand for construction of temporary overtopping protection bund using \u2018Sandbags\u201d,\nas and when required.<\/li><\/ol>\n\n\n\n
    • the stretch\nbetween the Ralapanawa and bitumen road be reserved for the construction of a\nwave wall to meet the dam safety requirements of future hydrological reviews to\nbe undertaken during the service life of the reservoir and bund.<\/li><\/ul>\n\n\n\n
      • a safe Load\nCapacity\u201d be imposed on the bund top road, and arrangements are made to stop\nall heavy trucks plying on the bund top road as the bund has not been designed\nfor such traffic loads.<\/li><\/ul>\n\n\n\n
        • the bund top\nroad is completely closed for all traffic (e.g., from 5:30 am to 7:30 am and\nfrom 6:00 pm to 9:00 pm, or as agreed by local authorities), in the\npreferred  2km long stretch, and then the\nexisting bitumen surfaced bund top road to be used as the walking path (alternatively,\nonly the upstream-half of the bitumen surfaced bund top road to be used as the\nwalking path while the downstream-half of the bitumen surfaced bund top road to\nbe kept open for one-way light traffic only, subject to nominated maximum speed\nto ensure the safety of people using the walking path).<\/li><\/ul>\n\n\n\n
          • an alternative\nwalking path (e.g., in the reservoir rim) be investigated, which will not compromise\nthe safety of the dam.<\/li><\/ul>\n\n\n\n
            • the\nreservation area located immediately downstream of the bund is not used for\ndevelopments that are been planned by the Urban Development Authority as this\narea is very sensitive to dam safety issues.<\/li><\/ul>\n\n\n\n
              • the\nreservation area located immediately downstream of the bund, which is an\nintegral component of the dam, be a property of the Irrigation Department for\ninspection and monitoring of critical dam safety features, construction of a\ntoe access road, construction of stabilising fills if required, stockpiling of\nconstruction materials required during dam emergencies etc.<\/li><\/ul>\n\n\n\n
                • a potential\nfailure modes analysis and Risk Assessment be undertaken in accordance with\ninternational dam safety standards.<\/li><\/ul>\n\n\n\n
                  • a Design and Safety\nReview of the dam and appurtenant structures be undertaken in accordance with\nthe international dam safety standards incorporating review of geotechnical\nparameters of the bund and foundation, hydrology, wave run-up, seismicity,\nflood handling capacity, reliability of gates and instrumentation etc.<\/li><\/ul>\n\n\n\n
                    1. sufficient\nfunds must be allocated to undertake Design and Safety Reviews of all Extreme\u201d\nconsequence category dams in Sri Lanka.<\/li><\/ol>\n\n\n\n
                      1. sufficient\nfunds must be allocated to routine maintenance of dams (note: depending on their nature, some maintenance items, if not addressed in a\nsystematic and timely manner, may eventually become dam safety issues,\neventually leading to failure of dams).<\/li><\/ol>\n\n\n\n
                        1. early arrangements\nmust be made to implement the recommendations of the Cabinet Memorandum No.\n11-2020 dated 26 October 2020 on the Establishment of a Dam Safety Consultation\nCentre and a Dam Safety Regulatory Mechanism.<\/li><\/ol>\n","protected":false},"excerpt":{"rendered":"

                          Bandula Kendaragama, Dam Safety Consultant, Melbourne, Australia This article is written based on information collated through consultations that were recently submitted as a technical report to His Excellency Gotabhaya Rajapaksaand other relevant government authorities. The consultations were among those who had been interested in dam safety and were directly involved in managing the Narrowly-Missed\u201d breach […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":true,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,158],"tags":[],"class_list":["post-119128","post","type-post","status-publish","format-standard","hentry","category-politics","category-technology"],"_links":{"self":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts\/119128","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/comments?post=119128"}],"version-history":[{"count":0,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/posts\/119128\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/media?parent=119128"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/categories?post=119128"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lankaweb.com\/news\/items\/wp-json\/wp\/v2\/tags?post=119128"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}