{ "bbox":null, "type":"Feature", "geometry":{ "bbox":null, "type":"Point", "coordinates":[ -93.71528, 34.14861 ] }, "properties":{ "provider":"MVK", "code":"Narrows Dam", "slug":"narrows%20dam", "elevation":0.0, "horizontal_datum":"NAD27", "vertical_datum":"NGVD29", "state":"AR", "kind":"PROJECT", "nearest_city":"Arkadelphia", "public_name":"Narrows Dam (Lake Greeson)", "location_code":11164013, "nsid":null, "aliases":{ "NIDID":"AR00154", "SHEF Location ID":"CE40B280", "DCP Platform ID":"CE40B280", "CWMS Legacy Naming":"Narrows Dam", "CWMS Standard Naming":"Narrows Dam" }, "timeseries":[ { "tsid":"Narrows Dam.%.Inst.1Hour.0.Percent Full", "label":"Percent Flood Pool", "base_parameter":"%", "parameter":"%", "unit":"%", "unit_long_name":"Percent", "latest_time":"2026-08-25T21:00:00Z", "latest_value":0.0, "delta24h":null, "sort_order":12, "results":null }, { "tsid":"Narrows Dam.Precip.Inst.1Hour.0.DCP-rev", "label":"Precipitation", "base_parameter":"Precip", "parameter":"Precip", "unit":"in", "unit_long_name":"Inches", "latest_time":"2026-08-25T21:00:00Z", "latest_value":21.23, "delta24h":null, "sort_order":16, "results":null }, { "tsid":"Narrows Dam.Elev.Inst.1Hour.0.DCP-rev", "label":"Elevation", "base_parameter":"Elev", "parameter":"Elev", "unit":"ft", "unit_long_name":"Feet", "latest_time":"2026-08-25T21:00:00Z", "latest_value":539.84, "delta24h":null, "sort_order":1, "results":null } ], "name":"Narrows Dam (Lake Greeson)", "hasResopsAverages":"true", "nidId":"AR00154", "nidid":"", "levels":[ { "slug":"elev.streambed", "label":"Streambed", "parameter":"Elev", "base_parameter":"Elev", "tsid":"Narrows Dam.Elev.Inst.0.Streambed", "latest_value":350, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"elev.top of conservation", "label":"Top of Conservation", "parameter":"Elev", "base_parameter":"Elev", "tsid":"Narrows Dam.Elev.Inst.0.Top of Conservation", "latest_value":548, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"elev.top of dam", "label":"Top of Dam", "parameter":"Elev", "base_parameter":"Elev", "tsid":"Narrows Dam.Elev.Inst.0.Top of Dam", "latest_value":581, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"elev.top of flood control", "label":"Top of Flood Control", "parameter":"Elev", "base_parameter":"Elev", "tsid":"Narrows Dam.Elev.Inst.0.Top of Flood Control", "latest_value":563, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"elev.top of power", "label":"Top of Power", "parameter":"Elev", "base_parameter":"Elev", "tsid":"Narrows Dam.Elev.Inst.0.Top of Power", "latest_value":548, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"elev.top of surcharge", "label":"Top of Surcharge", "parameter":"Elev", "base_parameter":"Elev", "tsid":"Narrows Dam.Elev.Inst.0.Top of Surcharge", "latest_value":580.2, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"stor.top of conservation", "label":"Top of Conservation", "parameter":"Stor", "base_parameter":"Stor", "tsid":"Narrows Dam.Stor.Inst.0.Top of Conservation", "latest_value":77600, "units":"ac-ft", "units_long_name":"Acre-feet", "type":"CONSTANT" }, { "slug":"stor.top of flood control", "label":"Top of Flood Control", "parameter":"Stor", "base_parameter":"Stor", "tsid":"Narrows Dam.Stor.Inst.0.Top of Flood Control", "latest_value":407900, "units":"ac-ft", "units_long_name":"Acre-feet", "type":"CONSTANT" }, { "slug":"stor.top of power", "label":"Top of Power", "parameter":"Stor", "base_parameter":"Stor", "tsid":"Narrows Dam.Stor.Inst.0.Top of Power", "latest_value":279700, "units":"ac-ft", "units_long_name":"Acre-feet", "type":"CONSTANT" }, { "slug":"stor.top of surcharge", "label":"Top of Surcharge", "parameter":"Stor", "base_parameter":"Stor", "tsid":"Narrows Dam.Stor.Inst.0.Top of Surcharge", "latest_value":320900, "units":"ac-ft", "units_long_name":"Acre-feet", "type":"CONSTANT" } ], "id":549792, "associatedStructuresCount":0, "conditionAssessDate":null, "conditionAssessDetail":null, "conditionAssessId":6, "damHeight":183, "damLength":940, "distance":5, "drainageArea":237, "eapId":1, "dsacAssignedDate":"2008-12-01T12:00:00.000Z", "eapMeetsGuidelinesId":0, "emergencyContactsUpdated":"2025-04-23T12:00:00.000Z", "eapLastRevDate":"1987-10-30T12:00:00.000Z", "enforcementAuthorityId":0, "federalId":"AR00154", "oldFederalId":"AR00154", "hazardId":4, "hydraulicHeight":187, "inspectionAuthorityId":0, "inspectionDate":"2020-07-09T12:00:00.000Z", "inspectionFrequency":5, "jurisdictionAuthorityId":0, "latitude":34.14859978, "lengthOfLocks":0, "secondaryLengthOfLocks":null, "longitude":-93.715643266, "maxDischarge":42300, "maxStorage":600600, "nidHeight":196, "nidStorage":600600, "normalStorage":279700, "numberOfLocks":0, "operationalStatusDate":"2008-12-01T12:00:00.000Z", "operationalStatusId":1, "originalDesignerName":null, "otherStructureId":null, "permittingAuthorityId":0, "politicalPartyId":null, "privateDamId":null, "projectDescription":"The U.S. Army Corps of Engineers (USACE) completed Narrows Dam in 1950 and continues to own, operate, and maintain the structure today. Located on the Little Missouri River in Pike County, Arkansas\u2014about 6 miles north of Murfreesboro\u2014the dam serves two primary purposes: flood control and hydroelectric power generation. The dam stands 183 feet tall and spans 928 feet in length, with a concrete gravity design. It impounds Lake Greeson and manages runoff from a drainage area of 237 square miles.\n\nNarrows Dam contains five structural sections: east and west bulkhead sections, a spillway section, a flood control section with Howell-Bunger valves, and a power section equipped with three 8,500-kW generating units. Together, these features allow USACE to control flows for downstream flood risk reduction while supplying renewable energy. The dam is also a popular site for outdoor recreation, including boating, fishing, and camping.\nWater stored in Lake Greeson is managed year-round to balance flood control storage, conservation pool levels for hydropower, and recreational needs. The flood control section is used periodically for managed releases through two conduits, controlled by Howell-Bunger valves. The power section discharges water through penstocks into a tailrace, generating an average of 158 million kilowatt-hours per year, which is enough to power 28,000 homes per year.\n\nThe foundation of Narrows Dam rests on the Jackfork sandstone formation, a strong bedrock unit typical of the Ouachita Mountains. A grout curtain, foundation drains, and monolith drains were incorporated into the design to control seepage. Monitoring instrumentation, including piezometers and settlement markers, continues to provide data on the dam\u2019s performance.", "riskCharSummary":"Narrows Dam is currently classified as a Dam Safety Action Classification (DSAC) 4 structure, meaning it has low urgency but requires continued maintenance and monitoring due to aging infrastructure and identified deficiencies. While the dam has performed reliably for more than 70 years, risk assessments conducted by USACE identified potential vulnerabilities. The most significant life safety risk-driver is: Global instability of a monolith at an intermediate lift joint during extreme pool loading, potentially leading to dam breach and uncontrolled release of water downstream. Additional potential failure modes relate to economic impacts, such as: Trash rack guide failure due to corrosion, allowing debris into turbines and causing costly outages, and Tailrace scour undermining structural integrity of retaining walls.\n\nStructural cracking, undercut riprap downstream, leaking joints, and spalled concrete have all been documented in recent inspections. Some instruments used to monitor performance, such as piezometers and joint reference markers, are outdated or insufficient. While seepage and leakage are currently manageable, their persistence underscores the importance of annual drain maintenance and continued surveillance.\nThe likelihood of dam failure remains remote, but consequences of breach would be significant. A failure could result in downstream flooding along the Little Missouri River, threatening lives, homes, highways, and power infrastructure. Although such an event is unlikely, dam breach flooding would occur rapidly and with limited warning.", "riskManagementMeasures":"To manage the risks associated with Narrows Dam, the U.S. Army Corps of Engineers (USACE) employs a comprehensive dam safety program that includes routine inspections, periodic assessments, performance monitoring through instrumentation, and close coordination with emergency management personnel. Although Narrows Dam has performed reliably since its construction in 1950, its age, structural complexity, and importance for both flood control and hydropower production necessitate proactive risk reduction efforts to ensure long-term safety and performance.\n\nTo address the risks identified at Narrows Dam, USACE has completed several critical actions and developed a forward-looking plan to reduce dam safety risk. Recent efforts include the investigation of a newly discovered concrete spall beneath a powerhouse beam, which was determined to be superficial. In addition, the Howell-Bunger valves underwent non-destructive testing, and the flood control stilling basin was dewatered and thoroughly inspected.\nPlanned improvements include upgrades to the dam\u2019s instrumentation network. This involves installing reference markers on the spillway weir to monitor for structural movement and replacing degraded tubing in the piezometer system. Rising head tests will help verify the accuracy of these devices. These instrumentation enhancements will strengthen the dam\u2019s ability to detect early signs of stress, seepage, or structural displacement.\nStructural integrity will be further assessed through a detailed crack mapping effort and a finite element analysis (FEA) focused on the upper inspection gallery. This analysis will simulate the dam\u2019s behavior under varying conditions, including seismic loads, to evaluate the potential for monolith instability and recommend mitigation strategies where needed.\nHydraulic infrastructure maintenance also plays a key role in risk management. Planned work includes video inspection and cleaning of the trash racks and tunnels in the power section. Damaged or missing trash rack guides will be replaced to prevent debris-related turbine issues. Known joint leaks behind the powerhouse and within the monoliths will be grouted and sealed, while new surface drainage features will redirect runoff away from critical areas of the powerhouse\nFoundation performance is managed through flushing of the monolith and foundation drains. Seepage at known leakage points will be addressed with grout or joint filler, and all surface drains will be cleaned to minimize the risk of erosion. In the tailrace, specialized camera inspections will examine potential undercutting of grouted riprap, which could impact structural stability if left unaddressed.", "riverName":"LITTLE MISSOURI RIVER", "separateStructuresCount":0, "sourceAgency":"US Army Corps of Engineers", "spillwayTypeId":3, "spillwayWidth":150, "stateFedId":"AR00154", "stateRegulatoryAgency":null, "stateRegulatedId":0, "structuralHeight":196, "submitDate":"2023-09-10T18:31:58.191Z", "surfaceArea":7200, "volume":300000, "widthOfLocks":0, "secondaryWidthOfLocks":null, "yearCompleted":1950, "congDist":"Congressional District 04, Arkansas", "city":"MURFREESBORO", "county":"Pike", "aiannh":null, "websiteUrl":"https://www.usace.army.mil/Missions/Civil-Works/Dam-Safety-Program/Article/2870967/dam-safety-program/", "coreTypeIds":"2", "damTypeIds":"9", "fedConstructionIds":"1", "fedDesignIds":"1", "fedFundingIds":"1", "fedInspectionIds":"1", "fedOperationIds":"1", "fedOtherIds":"1", "fedOwnerIds":"1", "fedRegulatoryIds":"1", "formerNames":null, "foundationTypeIds":"1", "nonFederalDamOnFederalId":0, "designerNames":"CEMVK", "otherNames":"Lake Greeson", "ownerNames":"USACE - Vicksburg District", "ownerTypeIds":"3", "primaryDamTypeId":9, "primaryOwnerTypeId":3, "primaryPurposeId":9, "purposeIds":"9;5;6", "dsacId":4, "femaRegion":"6", "lastEapExcerDate":"2015-05-28T12:00:00.000Z", "dataUpdated":"2025-07-01T12:00:00.000Z", "usaceDistrict":"Vicksburg District", "noConsequencesId":0, "secretaryAgricultureBuiltId":null, "nrcsWatershedAuthorizationId":null, "isAssociatedStructureId":"No", "fedRegulatedId":"Yes", "inundationNidAddedId":1, "damStatusId":2, "huc06":"080401", "doi_region":null, "doi_region_name":"Mississippi Basin", "doi_region_number":4, "thirtyYearAverage":704.9007, "tenthPercentile":666.5926, "ninetiethPercentile":760.1104 }, "id":11164013, "links":[ { "type":"application/json", "rel":"root", "title":"The landing page of this server as JSON", "href":"https://api.wwdh.internetofwater.app?f=json" }, { "type":"text/html", "rel":"root", "title":"The landing page of this server as HTML", "href":"https://api.wwdh.internetofwater.app?f=html" }, { "rel":"self", "type":"application/geo+json", "title":"This document as JSON", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/11164013?f=json" }, { "rel":"alternate", "type":"application/ld+json", "title":"This document as RDF (JSON-LD)", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/11164013?f=jsonld" }, { "rel":"alternate", "type":"text/html", "title":"This document as HTML", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/11164013?f=html" }, { "rel":"collection", "type":"application/json", "title":"USACE Access2Water API", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr" } ] }