{ "bbox":null, "type":"Feature", "geometry":{ "bbox":null, "type":"Point", "coordinates":[ -118.08389, 34.02028 ] }, "properties":{ "provider":"SPL", "code":"WN Rio Hondo", "slug":"wn%20rio%20hondo", "elevation":183.0, "horizontal_datum":"WGS84", "vertical_datum":"NGVD29", "state":"CA", "kind":"PROJECT", "nearest_city":"Pico Rivera", "public_name":"Whittier Narrows Dam Rio Hondo", "location_code":1064145, "nsid":null, "aliases":{ "NIDID":"CA10027" }, "timeseries":[ { "tsid":"WN Rio Hondo.Stor.Inst.~15Minutes.0.GOES-rev", "label":"Flood Storage", "base_parameter":"Stor", "parameter":"Stor", "unit":"ac-ft", "unit_long_name":"Acre-feet", "latest_time":"2026-04-14T22:30:00Z", "latest_value":5.39, "delta24h":null, "sort_order":11, "results":null }, { "tsid":"WN Rio Hondo.Flow.Inst.~15Minutes.0.GOES-rev", "label":"Outflow", "base_parameter":"Flow", "parameter":"Flow", "unit":"cfs", "unit_long_name":"Cubic feet per second", "latest_time":"2026-04-14T22:30:00Z", "latest_value":395.36, "delta24h":null, "sort_order":7, "results":null }, { "tsid":"WN Rio Hondo.Elev.Inst.~15Minutes.0.GOES-rev", "label":"Elevation", "base_parameter":"Elev", "parameter":"Elev", "unit":"ft", "unit_long_name":"Feet", "latest_time":"2026-04-14T22:30:00Z", "latest_value":185.62, "delta24h":null, "sort_order":1, "results":null }, { "tsid":"WN Rio Hondo.Precip.Inst.~15Minutes.0.GOES-rev", "label":"Precipitation", "base_parameter":"Precip", "parameter":"Precip", "unit":"in", "unit_long_name":"Inches", "latest_time":"2026-04-14T22:30:00Z", "latest_value":17.85, "delta24h":null, "sort_order":16, "results":null }, { "tsid":"WN Rio Hondo US.Flow.Ave.15Minutes.15Minutes.GOES-rev", "label":"Inflow", "base_parameter":"Flow", "parameter":"Flow", "unit":"cfs", "unit_long_name":"Cubic feet per second", "latest_time":"2026-04-14T22:30:00Z", "latest_value":394.74, "delta24h":null, "sort_order":6, "results":null } ], "name":"Whittier Narrows Dam Rio Hondo", "hasResopsAverages":"false", "nidId":"CA10027", "nidid":"", "levels":[ { "slug":"elev.bottom of flood", "label":"Bottom of Flood", "parameter":"Elev", "base_parameter":"Elev", "tsid":"WN Rio Hondo.Elev.Inst.0.Bottom of Flood", "latest_value":201.6, "units":"ft", "units_long_name":"Feet" }, { "slug":"elev.streambed", "label":"Streambed", "parameter":"Elev", "base_parameter":"Elev", "tsid":"WN Rio Hondo.Elev.Inst.0.Streambed", "latest_value":182.95, "units":"ft", "units_long_name":"Feet" }, { "slug":"elev.top of conservation", "label":"Top of Conservation", "parameter":"Elev", "base_parameter":"Elev", "tsid":"WN Rio Hondo.Elev.Inst.0.Top of Conservation", "latest_value":201.6, "units":"ft", "units_long_name":"Feet" }, { "slug":"elev.top of dam", "label":"Top of Dam", "parameter":"Elev", "base_parameter":"Elev", "tsid":"WN Rio Hondo.Elev.Inst.0.Top of Dam", "latest_value":239, "units":"ft", "units_long_name":"Feet" }, { "slug":"elev.top of flood", "label":"Top of Flood", "parameter":"Elev", "base_parameter":"Elev", "tsid":"WN Rio Hondo.Elev.Inst.0.Top of Flood", "latest_value":228.5, "units":"ft", "units_long_name":"Feet" }, { "slug":"stor.bottom of flood", "label":"Bottom of Flood", "parameter":"Stor", "base_parameter":"Stor", "tsid":"WN Rio Hondo.Stor.Inst.0.Bottom of Flood", "latest_value":2410, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.streambed", "label":"Streambed", "parameter":"Stor", "base_parameter":"Stor", "tsid":"WN Rio Hondo.Stor.Inst.0.Streambed", "latest_value":0, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.top of conservation", "label":"Top of Conservation", "parameter":"Stor", "base_parameter":"Stor", "tsid":"WN Rio Hondo.Stor.Inst.0.Top of Conservation", "latest_value":2410, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.top of dam", "label":"Top of Dam", "parameter":"Stor", "base_parameter":"Stor", "tsid":"WN Rio Hondo.Stor.Inst.0.Top of Dam", "latest_value":59674, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.top of flood", "label":"Top of Flood", "parameter":"Stor", "base_parameter":"Stor", "tsid":"WN Rio Hondo.Stor.Inst.0.Top of Flood", "latest_value":32217, "units":"ac-ft", "units_long_name":"Acre-feet" } ], "id":549751, "associatedStructuresCount":0, "conditionAssessDate":null, "conditionAssessDetail":null, "conditionAssessId":6, "damHeight":56, "damLength":16960, "distance":null, "drainageArea":554, "eapId":1, "dsacAssignedDate":"2016-05-24T12:00:00.000Z", "eapMeetsGuidelinesId":1, "emergencyContactsUpdated":"2025-04-22T12:00:00.000Z", "eapLastRevDate":"2019-10-31T12:00:00.000Z", "enforcementAuthorityId":0, "federalId":"CA10027", "oldFederalId":"CA10027", "hazardId":4, "hydraulicHeight":56, "inspectionAuthorityId":0, "inspectionDate":"2022-07-07T12:00:00.000Z", "inspectionFrequency":5, "jurisdictionAuthorityId":0, "latitude":34.0208974300001, "lengthOfLocks":0, "secondaryLengthOfLocks":null, "longitude":-118.054965372, "maxDischarge":307900, "maxStorage":66702, "nidHeight":56, "nidStorage":66702, "normalStorage":0, "numberOfLocks":0, "operationalStatusDate":"2016-05-24T12:00:00.000Z", "operationalStatusId":3, "originalDesignerName":null, "otherStructureId":null, "permittingAuthorityId":0, "politicalPartyId":null, "privateDamId":null, "projectDescription":"The U.S. Army Corps of Engineers Los Angeles District completed constructed Whittier Narrows Dam in 1957 by the spanning the San Gabriel River and Rio Hondo, near the cities of Pico Rivera and Montebello in Los Angeles County, California. The dam\u2019s primary purpose is to reduce the risk of flooding to more than 1 million people and an estimated $18 billion in property. In addition to flood risk management, Whittier Narrows Reservoir is used for recreation and water conservation in partnership with local agencies. Whittier Narrows Dam is made of compacted soil and rock. Overall, it is more than three miles long, and the top of the dam is about 55 feet above the Rio Hondo streambed. The reservoir is normally dry most of the year, but it is designed to capture water from storm events, which tend to be of short duration and high intensity. Whittier Narrows Dam is part of a complex waterway system that consists of several dams, levees and channels from the San Gabriel Mountains to the Pacific Ocean. Water flows along the San Gabriel River into the Whittier Narrows reservoir and exits into two rivers, the San Gabriel River and the Rio Hondo. Controlled releases are normally routed through the Rio Hondo\u2019s four outlet gates, and as needed, through the San Gabriel River Spillway gates, with only the amount of water the downstream channels can hold. The spillway structure is located to the east, on the San Gabriel River, and consists of nine large gates, which were designed to automatically operate in order to protect the dam from overtopping. This operation is needed to protect the earthen embankment of the dam from failure during extreme storm events, when the reservoir has the potential for filling up beyond its capacity.", "riskCharSummary":"In August 2019, USACE completed a safety study of Whittier Narrows Dam and classified the risk as extremely high. Although unlikely, a couple of dam failure scenarios triggered by rare, extremely high rainfall events, could lead to significant downstream flooding. These scenarios could occur when water exceeds the capacity of the reservoir and flows over the top of the dam, eroding it, or when water flows through the foundation beneath the dam, eroding it. If a dam failure were to occur, a wall of water would flood downstream areas, including many major roadways and highways that are considered evacuation routes. If the people downstream are unable to respond quickly and appropriately, they could be swept away by fast-moving water, which is forceful and deep enough to move vehicles within the flood area.\n\nWhen heavy rain occurs, Whittier Narrows Dam is designed to store excess rainfall runoff in the basin and then release the water to give swollen streams and rivers below the dam a chance to recede. Like all dams, Whittier Narrows Dam can only store so much water; the flood space is not infinite. Extreme weather can result in flood waters that can exceed the capacity of what the dam and basin are designed to retain. When this happens, water flows uncontrolled over the spillway to prevent a more destructive breach of the structure. When more water enters the basin than can be released from the dam, water could back up, exceed the basin\u2019s storage capacity and potentially result in flooding outside of the basin. Also, water could flow over the top of the dam, potentially resulting in a breach of the dam\u2019s earthen embankment, flooding downstream communities. These extreme weather events can potentially cause a significant threat to millions of people and billions of dollars in property damage, both downstream and upstream of the dam.", "riskManagementMeasures":"USACE is continually taking significant steps to reduce the risk to the public. This includes working closely with local emergency managers, regularly updating the Emergency Action Plan, and conducting emergency exercises with state and local response teams. All dam safety staff are regularly trained to monitor and evaluate the condition of the dam based on key risk components. USACE regularly inspects and monitors instruments to check the health of the dam and increase the frequency of this monitoring during lake levels rises, earthquake events, or other signs of distress. This ensures that the structure is performing as designed and could help detect any areas of potential concern. Regular maintenance and repairs are performed as needed to keep the dam functioning properly. Design of a long-term solution to address the concerns identified through the most recent risk assessment are currently under design. The USACE continues to inspect and monitor the dam while also evaluating potential interim risk reduction measures to reduce risk as low as possible until the design and construction are complete.", "riverName":"SAN GABRIEL RIVER", "separateStructuresCount":0, "sourceAgency":"US Army Corps of Engineers", "spillwayTypeId":1, "spillwayWidth":450, "stateFedId":"CA10027", "stateRegulatoryAgency":null, "stateRegulatedId":0, "structuralHeight":null, "submitDate":"2023-02-16T17:25:40.912Z", "surfaceArea":1, "volume":0, "widthOfLocks":0, "secondaryWidthOfLocks":null, "yearCompleted":1957, "congDist":"Congressional District 38, California", "city":"WHITTIER", "county":"Los Angeles", "aiannh":null, "websiteUrl":"https://www.spl.usace.army.mil/Missions/Asset-Management/Whittier-Narrows-Dam/", "coreTypeIds":null, "damTypeIds":"8", "fedConstructionIds":"1", "fedDesignIds":"1", "fedFundingIds":"1", "fedInspectionIds":"1", "fedOperationIds":"1", "fedOtherIds":"1", "fedOwnerIds":"1", "fedRegulatoryIds":"1", "formerNames":null, "foundationTypeIds":null, "nonFederalDamOnFederalId":0, "designerNames":"CESPL", "otherNames":"Whittier Narrows Reservoir", "ownerNames":"USACE - Los Angeles District", "ownerTypeIds":"3", "primaryDamTypeId":8, "primaryOwnerTypeId":3, "primaryPurposeId":9, "purposeIds":"9;5;8", "dsacId":1, "femaRegion":"9", "lastEapExcerDate":"2024-04-02T12:00:00.000Z", "dataUpdated":"2025-04-23T12:00:00.000Z", "usaceDistrict":"Los Angeles District", "noConsequencesId":0, "secretaryAgricultureBuiltId":null, "nrcsWatershedAuthorizationId":null, "isAssociatedStructureId":"No", "fedRegulatedId":"Yes", "inundationNidAddedId":1, "damStatusId":2, "huc06":"180701", "doi_region":"LCB", "doi_region_name":"Lower Colorado Basin", "doi_region_number":8 }, "id":1064145, "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/1064145?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/1064145?f=jsonld" }, { "rel":"alternate", "type":"text/html", "title":"This document as HTML", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/1064145?f=html" }, { "rel":"collection", "type":"application/json", "title":"USACE Access2Water API", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr" } ] }