APPENDIX G - DAM FAILURE AND LEVEE FAILURE PROFILES

1 Lehigh Valley Hazard Mitigation Plan

APPENDIX G - DAM FAILURE AND LEVEE FAILURE PROFILESDam Failure (p.2) Levee Failure (p.10)


4.3.16 Dam Failure4.3.16.1 Location and ExtentA dam is an artificial barrier that has the ability to store water, wastewater or liquid-borne materials for reasons that include, flood control, drinking water, water supply, energy generation, containment of mine tailings, recreation or pollution control. Many dams fulfill a combination of these stated functions (Association of State Dam Safety Officials 2013). Dam failures can result from one or a combination of the following reasons: n Overtopping caused by floods that exceed the capacity of the damn Deliberate acts of sabotagen Structural failure of materials used in dam constructionn Movement or failure of the foundation supporting the dam

n Settling and cracking of concrete or embankment damsn Piping and internal erosion of soil in embankment damsn Inadequate maintenance and upkeep (FEMA 2015)

Dam failures can cause serious downstream flooding either because of partial or complete dam collapse. Failures are usually associated with intense rainfall and prolonged flood conditions, but dam breaks may occur during dry periods as a result of progressive erosion of an embankment. The greatest threat from a dam break is to areas immediately downstream. According to the Pennsylvania Department of Environmental Protection, there are 101 dams in the Lehigh Valley as identified in Table 4.3.16.1 and shown in Figure 4.3.16.1.


Table 4.3.16.1 Dams in the Lehigh ValleyDam Name County Municipality Stream Type Class Permittee

Leaser Lake Lehigh Lynn Township Jacksonville Branch Ontelaunee Creek Earth B-1 PA Fish & Boat CommissionHosensack No 4 Lehigh Lower Milford Township Indian Creek Earth, Stone, Masonry C-1 Frank LunneyErrickson Fish Pond Lehigh Upper Saucon Township Tributary to Tumble Brook Earth C-1 Paul A BouisCedar Crest Boulevard Lehigh South Whitehall Township Jordan Creek tributary Earth C-1 South Whitehall TownshipMacArthur Towne Centre Lehigh Whitehall Township Lehigh River tributary Earth C-3 Mark Development CompanyFogelsville Pond Lehigh Upper Macungie Township Hassen Creek Masonry C-3 Upper Macungie TownshipHensingersville Lehigh Macungie Borough East Branch Swope Creek Earth, Concrete C-4 Alburtis Borough AuthorityLocust Valley Country Club Lehigh Upper Saucon Township Saucon Creek tributary Unavailable C-4 Locust Valley Country ClubLake Muhlenberg Lehigh Allentown City Cedar Creek Unavailable C-4 City of AllentownSchmidt Lehigh North Whitehall Township Unnamed Concrete, Earth C-4 Paul SchmidtPaul Krauss Lehigh Lynn Township Switzer Creek tributary Unavailable C-4 Paul KraussDetention Pond Lehigh Hanover Township Lehigh River tributary Earth C-4 Ms. Deanna L. BrandtGreen Hills Section 5 Lehigh Upper Macungie Township Iron Run tributary Earth C-4 Fred J. JaindlWest Detention Basin Lehigh Upper Macungie Township Iron Run tributary Earth C-4 Jaindl Land CompanyCoplay Creek Lehigh Whitehall Township Coplay Creek Concrete, Run of River C-4 Giant Portland Cement CompanyStabler Basin A Lehigh Upper Saucon Township Saucon Creek tributary Earth C-4 Valley Green at Stabler Center Homeowners Association Ernst Lehigh Washington Township Unnamed Earth C-4 Thomas ErnstStabler Basin 1 Lehigh Upper Saucon Township Saucon Creek tributary Earth C-4 Valley Green at Stabler Center Homeowners Association Trexler Park Pond Lehigh Allentown City Little Cedar Creek Concrete, Earth C-4 City of AllentownFurnace Street Lehigh Emmaus Borough Leibert Creek tributary Earth C-4 Borough of EmmausSchool Creek Lehigh Lynn Township School Creek Unavailable C-4 James & Pat HoffmanGiacobbe Lehigh Washington Township Mill Creek tributary Unavailable C-4 F. J. GiacobbePfeiffer Pond Lehigh Heidelberg Township Jordan Creek tributary Earth C-4 Karen PfeifferEssroc Lehigh Whitehall Township Coplay Creek C-4 Essroc Italcementi GroupSpring Mill Lehigh Whitehall Township Spring Creek Earth, Masonry, Rockfill C-4 Northampton Borough Municipal Water AuthorityBuilders Square Lehigh South Whitehall Township Cedar Creek tributary Earth C-4 Powerline Associates, L.P.Mill - Dorney Park Lehigh South Whitehall Township Cedar Creek Gravity C-4 Dorney Park/Wildwater KingdomHamilton Street Lehigh Allentown City Lehigh River Concrete, Gravity C-4 City of AllentownTrout Creek Reservoir Lehigh Heidelberg Township Trout Creek Stone, Masonry, Earth C-4 Heidelberg Game Protective AssociationMill Lehigh Allentown City Little Lehigh Creek Concrete C-4 City of AllentownMill Lehigh Lower Macungie Township Little Lehigh Creek Concrete C-4 Cordes & Kimberly K. Snyder III Mill Lehigh Lower Macungie Township Little Lehigh Creek Concrete C-4 Mark P. & Ellyn G. ElsteinMill Lehigh Lower Macungie Township Little Lehigh Creek Concrete C-4 John Gallagher And Deana ZoskyIce Lehigh Upper Milford Township Leibert Creek Concrete, Gravity C-4 David & Barbara BollingerJordan Park Lehigh Allentown City Jordan Creek Stone, Masonry, Run of River C-4 City of Allentown


Table 4.3.16.1 Dams in the Lehigh Valley

Little Lehigh Lehigh Allentown City Little Lehigh Creek Concrete C-4 City of AllentownMill Lehigh Weisenberg Township Schaefer Run Earth C-4 Sue UbbenBig Bed Slate Lehigh Washington Township Trout Creek Concrete, Gravity C-4 Penn Big Bed Slate Co.Kemmerling Lehigh Lynn Township Ontelaunee Creek Concrete, Run of River C-4 Nevin & Helen KemmerlingCrowley Lehigh Weisenberg Township Lyon Creek Concrete, Gravity C-4 Patrick Crowley, Jr.Kerns Lehigh North Whitehall Township Jordan Creek Concrete C-4 Fred JaindlNorthampton Lehigh Whitehall Township Lehigh River Concrete C-4 Whitehall Cement Manufacturing CompanyMill Lehigh North Whitehall Township Coplay Creek Concrete C-4 Terry MuthWehrs Lehigh South Whitehall Township Jordan Creek Concrete C-4 South Whitehall TownshipMinsi Lake Northampton Upper Mount Bethel Township East Branch Martins Creek Earth B-1 PA Fish & Boat CommissionMartins Creek SES Northampton Lower Mount Bethel Township Oughoughton Creek tributary Earth B-1 PPL Martins Creek, LLC Ash Basin No 4Chain Northampton Palmer Township Lehigh River Stone, Masonry B-4 PADEP Rolling Greens Northampton Bethlehem Township Nancy Run tributary Earth C-1 Bethlehem Township(Bethlehem Twp. Detention)West Side Detention Northampton Roseto Borough Martins Creek tributary Earth C-1 Borough of RosetoPalmer Park Mall Northampton Palmer Township Bushkill Creek tributary Earth C-3 Palmer Park Mall VentureQuail Hollow Northampton Bethlehem Township Lehigh River tributary Earth C-3 4-L Housing AssociatesDetention BasinEcho Lake Northampton Upper Mount Bethel Township Jacoby Creek tributary Earth, Rockfill C-3 Echo Lake Development Co. Inc. Kings Crossing Northampton Bethlehem Township Lehigh River tributary Earth C-3 Bethlehem TownshipUpper Northampton Easton City Bushkill Creek Concrete C-4 Specialty Minerals, Inc. Emery Northampton Portland Borough Jacoby Creek Masonry C-4 M.C. EmeryWagner Farms Northampton Bethlehem Township Lehigh River tributary Earth C-4 Wagner Enterprises, Ltd.Detention BasinWater Power Northampton Palmer Township Bushkill Creek Concrete C-4 Upper Mill LPHemlock Brook Northampton Upper Mount Bethel Township Hemlock Brook Earth C-4 Garofalo RealtyLappawinzo Northampton Allen Township Hokendauqua Creek Stone, Masonry, Run of River C-4 Lappawinzo Rod And Gun ClubGrays Pond Northampton Hellertown Borough Reservoir Creek Earth C-4 Hellertown Borough AuthorityInter-Club Northampton Freemansburg Borough Nancy Run Unavailable C-4 Inter-Club Canal Commission, Inc.Jacoby Creek Northampton Upper Mount Bethel Township Jacoby Creek Earth C-4 Upper Mount Bethel Development Group, Inc.Ratcliffe Northampton Washington Township Oughoughton Creek tributary Earth C-4 Ms. Sheri LobbStephen Demshock Northampton Lower Nazareth Township East Monocacy Creek tributary Earth C-4 Stephen DemshockPenns Farm Northampton Bethlehem Township Nancy Run tributary Earth C-4 Penns Farms Condominium Detention Basin AssociationCole Northampton Upper Mount Bethel Township Allegheny Creek tributary Earth C-4 Charles ColePond No 2 Northampton Hanover Township Monocacy Creek tributary Earth C-4 Pointe AssociatesLake Je-Ba-Ru Northampton Upper Mount Bethel Township Jacoby Creek Earth C-4 Stabler Development Co.

Dam Name County Municipality Stream Type Class Permittee

5 Lehigh Valley Hazard Mitigation Plan 4 Lehigh Valley Hazard Mitigation Plan

Table 4.3.16.1 Dams in the Lehigh Valley

Rouse and Associates Northampton Hanover Township Monocacy Creek tributary Earth C-4 Rouse & AssociatesSubdivision #1Rouse Detention Northampton Hanover Township Monocacy Creek tributary Earth C-4 Liberty PropertyBasin No. 2 Limited PartnershipLehigh Valley Industrial Northampton Hanover Township Monocacy Creek tributary Earth C-4 Micro Specialty SystemPark IIILehigh Valley Industrial Northampton Hanover Township Monocacy Creek tributary Earth C-4 Lehigh Valley Industrial ParkPark IVWalnut Hills Detention Northampton Bethlehem Township Lehigh River tributary Earth C-4 Sam Calantoni Delaware Trace Northampton East Allen Township Lehigh River tributary Earth C-4 Ronald And Marilyn BauerDetention BasinLaneco Plazan Northampton Lower Nazareth Township Shoeneck Creek tributary Unavailable C-4 Laneco Pad LP Detention BasinChrin Brothers Northampton Williams Township Tumble Creek Earth C-4 Chrin Brothers, Inc.Lehigh Canal Lock 41 Northampton Bethlehem City Lehigh River Canal Masonry, Timber Crib C-4 City of BethlehemSchiavone Northampton Plainfield Township Bushkill Creek tributary Rockfill C-4 Allen FloryWater Supply Northampton Northampton Borough Hokendauqua Creek Gravity C-4 Horwith Leasing Co. Inc.Walters Mill Pond Northampton Palmer Township Bushkill Creek Concrete C-4 Palmer TownshipUpper Northampton Easton City Bushkill Creek Concrete C-4 Excalibur Realty CompanyMartins Creek Ash Northampton Lower Mount Bethel Township Oughoughton Creek Other, Earth C-4 PPL Martins Creek, LLC Basin No. 1Dewalt Northampton Easton City Bushkill Creek Unavailable C-4 Scott DewaltLower Northampton Easton City Bushkill Creek Concrete C-4 Easton Municipal AuthorityLafayette College Northampton Easton City Bushkill Creek Unavailable C-4 Lafayette CollegeMill Northampton Lower Saucon Township Saucon Creek Unavailable C-4 G.A. KeckMill Northampton Hanover Township Monocacy Creek Concrete C-4 Lee & Sally SnyderMill Northampton Hanover Township Monocacy Creek Concrete C-4 St. Francis RetreatCohen Northampton Lower Saucon Township Black Creek Earth C-4 Martin & Susan CohenMill Northampton Hanover Township Monocacy Creek Concrete C-4 Leon A.C. & Beverly IsaacEaston Northampton Easton City Lehigh River Stone, Masonry C-4 PA DCNR Field Northampton Palmer Township Bushkill Creek Concrete C-4 Richard L. FieldMill Northampton Bushkill Township Bushkill Creek Concrete C-4 Mary Ann OrsingerMill Northampton Lower Mount Bethel Township Martins Creek Concrete, Masonry C-4 Dina PlebaniIce-Fish Northampton Upper Mt Bethel Township Martins Creek Earth C-4 Barbara PaulIllicks Mill Northampton Hanover Township Monocacy Creek Earth, Stone, Masonry C-4 City of BethlehemMonocacy Creek Northampton Bethlehem City Monocacy Creek Stone, Masonry C-4 City of BethlehemMinch Spring Run Northampton Upper Mount Bethel Township Minch Spring Run Stone, Masonry C-4 Portland Borough AuthorityBeersville Grove Northampton Moore Township Hokendauqua Creek tributary Concrete, Gravity C-4 Beersville Grove, Inc.Peppell Northampton Bushkill Township Bushkill Creek tributary Earth C-4 James & Virginia PeppellMill Northampton Hanover Township Monocacy Creek Concrete C-4 Eastlake Montessori Education Center, Inc.

Dam Name County Municipality Stream Type Class Permittee


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Figure 4.3.16.1 Dams in the Lehigh Valley

Source: PA DEP Dam Safety



4.3.16.2 Range of MagnitudeThe PADEP Division of Dam Safety provides for the regulation and safety of dams and reservoirs throughout the Commonwealth to protect the health, safety and welfare of its citizens and their property. This division is required to assure proper planning, design review, construction review, maintenance monitoring and

supervision of dams and reservoirs. Dams are classified by size and hazard potential as shown in Table 4.3.16.2. Hazard Category 1 and 2 dams are considerd high hazard dams. Owners of dams classified as Hazard Categories 1 or 2 are required to create an Emergency Action Plan (EAP) that describes the dam, the inundation area if the dam fails, and procedures for responding to the dam failure, such as notification to vulnerable populations.

Source: 025 Pa. Code § 105.91. http://www.pacode.com/secure/data/025/chapter105/s105.91.html

Table 4.3.16.2 Dam Classification Definitions

CategoryImpoundment Storage

(Acre feet)

Size CategoryDam Height (Feet)

A

B

C

1

2

3

4

Equal to or greater than 50,000

Less than 50,000, but greater than 1,000

Equal to or less than 1,000

Equal to or greater than 100

Less than 100, but greater than 40

Equal to or less than 40

Substantial (Numerous homes or small businesses or a large

business or school).

Few (A small number of homes or small businesses.)

None expected (no permanent structures for human habitation or

employment.)

None expected (no permanent structures for human habitation or

employment.)

Excessive such as extensive residential, commercial, or agricultural damage, or

substantial public inconvenience.

Appreciable such as limited residential, commercial, or agricultural damage, or

moderate public inconvenience.

Significant damage to private or public property and short duration public inconvenience such as

damage to storage facilities or loss of critical stream crossings.

Minimal damage to private or public property and no significant public inconvenience.

Category Population at Risk

Hazard Potential Category

Economic Loss

8 Lehigh Valley Hazard Mitigation Plan 7

Based on the PADEP classification, there are eight high hazard dams in the Lehigh Valley:n Hosensack No. 4: Permitted by a private resident and is located on Indian Creek in Lower Milford Township, Lehigh County. Classified as C-1.n Leaser Lake: Permitted by the PA Fish & Boat Commission and is located on the Jacksonville Branch of Ontelaunee Creek in Lynn Township, Lehigh County. Classified as B-1.n Cedar Crest Boulevard: Permitted by South Whitehall Township and is located on a tributary of Jordan Creek in South Whitehall Township, Lehigh County. Classified as C-1.n Errickson Fish Pond: Permitted by a private resident and is located on a tributary of Tumble Brook in Upper Saucon Township, Lehigh County. Classified as C-1.n Rolling Greens: Permitted by Bethlehem Township and is located on a tributary of Nancy Run in Bethlehem Township, Northampton County. Classified as C-1.n Martin’s Creek SES Ash Basin No. 4: Permitted by PPL Martins Creek, LLC and is located on a tributary of Oughoughton Creek in Lower Mount Bethel Township, Northampton County. Classified as B-1.n West Side Detention: Permitted by the Borough of Roseto and is located on a tributary of Martins Creek in Roseto Borough, Northampton County. Classified as C-1.n Minsi Lake: Permitted by the PA Fish & Boat Commission and is located on the East Branch

Martins Creek in Upper Mount Bethel Township, Northampton County. Classified as B-1 (PA DEP Dam Safety).

Dam failures often release the reservoir of water stored upstream of the dam, severely impacting plant and animal life dependent on the aquatic system. The subsequent rush of water downstream can rapidly increase flow rate and turbidity of streams and rivers in minor dam failures or overwhelm terrestrial habitat with floodwaters in severe dam failure events. Dam failures can often result in the release of hazardous materials, either swept up in floodwaters or in sediment that is contained behind the dam as is often the case in areas that have had mining activities take place upstream. After the floodwaters subside, contaminated and flood damaged building materials and contents must be properly disposed. Contaminated sediment must be removed from buildings, yards and properties. Environmental impacts of flooding of terrestrial habitats from dam failure are similar to other flooding events. For environmental impacts of flooding, refer to the Flood profile. Other potential secondary hazards of dam failure are landslides around the reservoir perimeter, bank erosion on the rivers and destruction of downstream habitat. 4.3.16.3 Past OccurrenceThere have been no recorded dam failures in the Lehigh Valley. However, it is noted that the Lake Minsi Dam, which is categorized as a high hazard dam in Upper Mt. Bethel Township, was deemed unsafe due to limited spillway capacity. The lake was drained in 2017 for the dam to be repaired. The lake and dam are owned by the Pennsylvania Fish and Boat Commission (Northampton County 2018).



4.3.16.4 Future OccurrenceThe likelihood of a dam failure in the Lehigh Valley is extremely difficult to predict. However, the risk of such an event increases for each dam as the dam’s age increases. Based on the Lehigh and Northampton County Emergency Management Agencies’ operational viewpoint, the probability of occurrence for dam failure events in the Lehigh Valley is considered ‘unlikely,’ as defined in Section 4.4.2. 4.3.16.5 Vulnerability AssessmentThe dam failure hazard is of significance to the Lehigh Valley because there are 101 dams across Lehigh and Northampton counties, eight of which are classified as ‘high hazard’ by the PADEP. Overall, the Lehigh Valley’s vulnerability has not changed since the 2013 Plan, and the areas of the region located in and around dams continue to be exposed and vulnerable to the dam failure hazard.Spatial dam failure inundation areas are considered sensitive information and were not used to assess risk for the 2018 Plan. Therefore, a qualitative assessment was conducted to evaluate the assets exposed and the potential impacts associated with this hazard. The direct and indirect losses associated with dam failures include injury and loss of life, damage to structures and infrastructure, agricultural losses, power outages and stress on community resources. A dam failure can also result in the displacement of those living in the inundation

area. Emergency medical care, food and temporary shelters may be required for injured or displaced persons. All people, buildings and infrastructure in a dam failure inundation zone are considered exposed and vulnerable. Of the population exposed, the most vulnerable include the economically disadvantaged and people over the age of 65. Economically disadvantaged populations are more vulnerable because they are likely to evaluate their risk and make decisions to evacuate based on the economic impact to their family. People over the age of 65 are also highly vulnerable because they are more likely to seek or need medical attention, which may not be available due to isolation during a flood event, and they may have more difficulty evacuating. There is often limited warning time for a dam failure. These events are frequently associated with other natural hazard events such as earthquakes, landslides or severe weather, which limits their predictability and compounds the hazard. Properties located closest to the dam inundation zone have the greatest potential to experience the largest, most destructive surge of water. Damage to transportation infrastructure in the dam inundation area could cut off evacuation routes, limit emergency access and create isolation issues. Utilities such as overhead power lines, and cable and phone lines could also be vulnerable. Loss of these utilities could create additional isolation issues for the inundation zones.


4.3.20 Levee Failure4.3.20.1 Location and ExtentLevees are typically barriers between floodwaters and the built landscape. They include a series of culverts, canals, ditches, storm sewers or pump stations, called “interior drainage” systems. These systems channel water from the land side of a levee over to the water side. When floodwaters exceed the height of a levee, overtopping occurs. As the water passes over the top, it can erode the levee, worsening the flooding and potentially causing an opening or breach in the levee. A levee breach occurs when part of a levee gives way, creating an opening through which floodwaters may pass. A breach can occur gradually or suddenly. The most dangerous breaches happen quickly during periods of high water. The resulting torrent can quickly swamp a large area behind the failed levee with little to no warning (American Society of Civil Engineers 2010).As per the National Committee on Levee Safety, levees,

when functioning properly, reduce the risk of flooding for communities. However, an unexpected levee breach or failure can be catastrophic, with the flooding causing loss of life, emergency evacuations and insufficient time to reduce damages to property.FEMA completed an inventory of all known levees across Pennsylvania in 2009 with an update in 2012, known as the Mid-Term Levee Inventory (MLI). The MLI contains levee data gathered primarily for structures designed to protect from the 1% annual chance flood event. The area behind a maintained and certified levee that is designed to protect from a 1% annual chance flood is called a Levee Protected Area. The MLI also frequently includes levees that were not designed to protect against this base flood, but the MLI does not include every levee in every county—especially small levees and agricultural levees not engineered or able to be accredited to the 1% annual chance event (FEMA, 2011). FEMA’s inventory was


compiled using all effective Flood Insurance Rate Maps and Flood Insurance Study reports in Pennsylvania, the US Army Corps of Engineers (USACE) levee inventory, the Pennsylvania Department of Environmental Protection (PADEP) Flood Control Project summaries, information from local governments, aerial photography, and information such as news articles and websites (PEMA 2013).There are four USACE levees or floodwalls in the Lehigh Valley: Allentown (Sewer Treatment Plant) Levee, Salisbury Levee, Allentown-Jordan Creek Floodwall and Bethlehem Levee System as shown in Figures 4.3.20.1 through 4.3.20.4, respectively (R3Levees, 2009). As presented in the FEMA Flood Insurance Studies for Lehigh and Northampton counties, there are additional

levees located in the Lehigh Valley. In the City of Allentown, there is a 750-foot low levee along the right bank of the Lehigh River, a concrete floodwall extending 204 feet upstream of the Old Hamilton Street bridge, a short levee spanning 69 feet between the abutment of the Old and New Hamilton Street bridges, a levee extending 1,125 feet connecting with Kline’s Island Levee, and a training dike approximately 1,300 feet long that was constructed around a sharp bend to reduce backwater stages in Little Lehigh Creek. A straightened and deepened main channel, extending 8,280 feet, is another local flood control project within Allentown.In Salisbury Township, a dike was built along the south side of the Lehigh River to protect the floodplain in the loop of the river (FEMA 2004).


Figure 4.3.20.1 Allentown (Sewer Treatment Plant) Levee


Figure 4.3.20.2 Salisbury Levee


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Figure 4.3.20.3 Jordan Creek Floodwall



Figure 4.3.20.4 Bethlehem Levee System


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A complete levee failure, like a dam failure, is rather infrequent and typically coincides with heavy rainfall, storm surge or hurricanes. In the event of a levee failure, floodwaters may ultimately inundate the protected land near the levee. The extent of inundation is dependent on the flooding intensity. Failure of a levee during a 1% annual chance flood will inundate the approximate 100-year floodplain previously protected by the levee. Residential and commercial buildings located nearest the levee overtopping or breach location will suffer the most damage from the initial embankment failure flood wave. Landward buildings will be damaged by inundation (FEMA 2004).Levees require maintenance to continue to provide the level of protection they were designed and built to offer. Maintenance responsibility belongs to a variety of entities including local, state and federal government, and private landowners. Well-maintained levees may obtain certification through independent inspections. Levees may not be certified for maintaining flood protection when the levee owner does not maintain the levee or pay for an independent inspection. The impacts of an uncertified levee include higher risk of levee failure. In addition, insurance rates may increase because FEMA identifies on Flood Insurance Rate Maps that the structures are not certified to protect from a 1% annual chance flood event (FEMA 2004).4.3.20.2 Range of MagnitudeFlood-related hazards due to levees range in magnitude from overtopping, to water flowing around the back of the levee outside of the edge of the levee system, to total failure as seen during Hurricane Katrina (PEMA 2013). Levees are typically designed with three feet of freeboard to prevent overtopping, but older levees were not built

to that standard. The failure of a levee or other flood protection structure could be devastating depending on the level of flooding for which the structure is designed and the amount of development present. In some instances, the magnitude of flooding could be more severe under a levee failure event compared to a normal flooding event. If an abrupt failure occurs, the rushing waters of a flood wave could result in catastrophic losses (PEMA 2013).The worst-case levee failure is one which occurs abruptly with little warning and results in deep, fast-moving flood waters through a highly-developed or highly-populated area. While any levee may be overtopped and fail, it is these levees with large protected areas that have the potential to cause the most damage (PEMA 2013). If the levee failure is caused by overtopping, the community may not be able to recognize the impending failure and evacuate. If a levee failure occurs suddenly, evacuation may not be possible.Failure of the Allentown (Sewer Treatment Plant) Levee or the Salisbury Levee would affect only the individual facilities that they protect—the Allentown Sewer Treatment Plant and the Lehigh County Men’s Community Correction Center. Flooding of the Allentown Sewer Treatment Plant would affect a large number of people in the area in and around the City of Allentown. It would likely result in widespread contamination of the floodwaters and, potentially, the drinking water supply if contamination from the sewer plant reached a drinking water system intake. The public may be advised to boil water before using it to drink or cook. Additional limitations on water usage may also be issued. Flooding of the Men’s Community Correction Center would impact the center’s population and staff. Evacuation of the facility may be necessary.


Neither the Jordan Creek Floodwall nor the Bethlehem Levee System is shown on the official Digital Flood Insurance Rate Maps (DFIRMs). That is, flood zones on the DFIRMs do not account for the levees’ existence. Therefore, if they failed during the 1% annual chance flood, the floodwaters would reach the areas shown on the DFIRMs as being within the 1% annual chance floodplain. Either of these levees failing is considered a worst-case scenario. See the Flood profile for a description of flood events in the Lehigh Valley. The environmental impacts of a levee failure include significant water quality and debris disposal issues. Flood waters will back up sanitary sewer systems and inundate wastewater treatment plants, causing raw sewage to contaminate residential and commercial buildings and the flooding waterway. The contents of unsecured containers of oil, fertilizers, pesticides and other chemicals get added to flood waters. Water supplies and wastewater treatment could be off-line for weeks. After the flood waters subside,

contaminated and flood damaged building materials and contents must be disposed of properly. Contaminated sediment must be removed from buildings, yards and properties. Levee failure can also cause landslides, bank erosion and destruction of habitat. 4.3.20.3 Past OccurrenceThere have been no levee failures in the Lehigh Valley. 4.3.20.4 Future OccurrenceBased on the Lehigh and Northampton County Emergency Management Agencies’ operational viewpoint, the probability of occurrence for levee failure events in the Lehigh Valley is considered ‘unlikely’ as defined in Section 4.4.2. 4.3.20.5 Vulnerability AssessmentThe extent of a levee failure inundation is dependent on the flooding intensity. Failure of a levee during a 1% annual chance flood will inundate the 1% annual chance


floodplain previously protected by the levee. Residential and commercial buildings located nearest the levee overtopping or breach location will suffer the greatest damage from the initial embankment failure flood wave. (PEMA, 2013). Similar to dam failures, people living in the inundation path and those living downstream of a levee are at risk and will need to evacuate in the event of a failure or breach. Areas, structures and population located downstream of a levee are vulnerable if a failure were to occur. Additionally, failure of levees during a 1% annual chancel flood event would result in flood waters reaching the areas shown on the DFIRMs. Overall, the Lehigh Valley’s vulnerability has not changed since the 2013 Plan, and the areas located around levees continue to be exposed and vulnerable to the levee failure hazard.

Levee failure inundation areas were not available to conduct a spatial assessment to estimate potential impacts for the 2018 Plan. The 2013 Pennsylvania All-Hazard Mitigation Plan identified five critical facilities in Lehigh County and two in Northampton County that are either in a levee protected area or within 2,000 feet of the levee system. Using a 2,000-foot buffer, the 2013 PA plan also estimated jurisdictional losses. For Lehigh County there are 5,686 impacted buildings with an exposure value for building and contents of about $1.4 billion, and for Northampton County there are 4,088 impacted buildings with an exposure value for building and contents of about $935 million. It is important to note that for the building and exposure analysis, only the 2,000-foot buffer was used as not all levees have Levee Protected Areas.

APPENDIX G - DAM FAILURE AND LEVEE FAILURE PROFILES

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Transcript of APPENDIX G - DAM FAILURE AND LEVEE FAILURE PROFILES