Minimizing Roadway Embankment Damage from Flooding (2016)

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14 CHAPTER THREE CASE EXAMPLES Quick action was taken to armor and protect the stretches of damaged road. FIGURE 13 Damage from Hurricane Dennis (2005) along US- 98, Franklin County, Florida (Courtesy of Florida DOT). Funding Aspect Franklin County was declared as one of 13 federal disaster areas in Florida after Hurricane Dennis hit the coast. As a result, the county could use FEMA emergency funds to restore and rebuild important public facilities. The US-98 Carrabelle Revetment project was carried out using FEMA funds. Techniques Used The repair work allowed for betterments, including armoring the embankment with sheet piling, soldier piling, articulated concrete blocks, and miscellaneous asphalt and performance turf. Figures 14 through 16 illustrate typical sections of the countermeasures adopted in this project. Figure 17 shows the construction process. Figure 18 shows a completed sec- tion of the embankment. The countermeasures were selected with consideration of the right-of-way limitations. Where a slope of 1V to 3H is possible, articulated concrete blocks were installed on the slope above an 18-in.-thick layer of bedding stones placed over filter fabric (Figure 14). Bermuda sod placed over jute and polymer were used in the finishing soil layer (Figure 15). Figure 16 shows articulated concrete blocks installed down the seaward slope until the edge INTRODUCTION This chapter presents 14 case examples gathered from the following six states: Florida, Wyoming, Minnesota, Colo- rado, Maryland, and West Virginia. To complement the information obtained through the survey, five interviews were conducted with relevant practicing DOT engineers from the aforementioned states (except Florida) who were involved in the case examples. In Florida, a major highway, US-98, suffered severe damage from coastal wave action. In Wyoming, four riverine roadway embankments suffered damage from overtopping. Four overtopping case examples were provided by Minnesota, one of which involved overtop- ping resulting from wave action. Three cases from arid can- yon environments in Colorado are discussed. These cases illustrate the challenges imposed by high-velocity streams, changes in river alignment, and steep embankment slopes. One case is included from Maryland, in which erosion of the embankment riverside slope called for construction of a stone wall to protect the embankment slopes, as explained in “Techniques Used.” Lastly, the Kimsey Run project in West Virginia represents a river relocation and stabilization case to protect the embankment from the river. The causes of damage, the protection and stabilization methods selected, and an evaluation of the systems used based on the inter- views conducted are presented. A summary of the causes of damage and the selected protection and stabilization mea- sures is included at the end of this chapter. WAVE EROSION OF A COASTAL HIGHWAY, FLORIDA The data were provided by documents received from Flor- ida DOT. This case example describes severe damage to a stretch of State Route 30 (US-98) that was caused by Hur- ricane Dennis. The cause of damage, funding aspect, repair techniques used, and damage from consequent storms are further described here. Cause of Damage State Route 30 (US-98) is a major coastal highway in Frank- lin County, Florida. When Hurricane Dennis struck in 2005, a 14.6-mi stretch of this highway suffered significant damage from wave action and overtopping mechanisms resulting in erosion. Figure 13 shows the damage on the seaward slope.

15 FIGURE 14 Typical armoring detail 1 for 1:3 slopes or flatter (Courtesy of Florida DOT). FIGURE 16 Typical armoring detail 2 for slopes steeper than 1:3 (Courtesy of Florida DOT).

16 of the pile cap. Starting from the other face of the piles (seaward face), riprap was placed over an 18-in. layer of bedding stone that was spread over filter fabric. Figures 17 and 18 show the road under construction and reconstructed, respectively. FIGURE 15 Typical vegetation section (Courtesy of Florida DOT). FIGURE 17 Construction of stabilized roadway section (Courtesy of Florida DOT). FIGURE 18 Roadway after completion of repair work (Courtesy of Florida DOT). Damage from Subsequent Storms Damage from subsequent storms was limited to loss of top- soil and reinforcement turf on the seaward slopes, shown in Figure 19. FIGURE 19 Damage limited to the removal of performance turf and topsoil after armoring (Courtesy of Florida DOT). OVERTOPPING EROSION OF A RIVERINE HIGHWAY, WYOMING The case examples discussed in this section include Childs Draw (Cheyenne), Sand Draw Highway 487, Unnamed Draw Highway 136 (Gas Hill Road near Riverton), and Rock Creek. Childs Draw, Cheyenne This newly constructed site is characterized by low fill height. This embankment was designed to sustain overtop- ping. The downstream slope was protected with gabions (wire-enclosed riprap). The site successfully withstood overtopping and no damage occurred. Sand Draw Highway 487 A severe flood resulting from rain and snow overtopped the roadway and nearly breached the embankment. Although the exact cause is unknown, overtopping could have occurred as a result of an undersized culvert (it was designed for a 25-year event) or from the culvert being blocked with ice jam. An additional culvert barrel was added to prevent over- topping. No embankment protection was installed. For the past 30 years, the site has not experienced any overtopping. Unnamed Draw Highway 136 (Gas Hill Road Near Riverton) This roadway was overtopped during severe flooding likely compounded by an undersized culvert. No embankment pro- tection was installed at the time of the initial design. The down- stream slope was repaired by installing gabions. Since then, the site has survived overtopping events without any damage. Rock Creek On June 10, 1986, this highway was overtopped because of an upstream dam breach. Overtopping led to damage and

17 the state DOT is now preparing adequate repair measures. Gabions are proposed for this site. DAMAGE RESULTING FROM OVERTOPPING AND WAVE ACTION OF RIVERINE HIGHWAYS, MINNESOTA Four case examples from Minnesota are presented herein. TH-220 north of Oslo is an example of wave action inflicting damage on the embankment slopes facing the waves. TH-1 east of Oslo, TH-9 south of Ada, and TH-200 west of Ada are examples of overtopping and associated damage. In gen- eral, failure resulting from overtopping is the most promi- nent roadway embankment problem caused by flooding in the northern Red River Valley. Other parts of Minnesota are subject to summer flash flooding and have steeper terrain and shorter flooding durations. Accordingly, flooding lasted several weeks in the Oslo case examples but only a few days in the Ada cases. TH-220 North of Oslo In this case, damage on the downstream slope was caused primarily by wave overtopping. The damage to the unpro- tected downstream slope is shown in Figure 20. In this case, paving the downstream slope of the embankment mini- mized the damage caused by wave action. Figure 21 shows the actual paving of the embankment slope, and Figure 22 shows the minimal damage sustained during a subsequent flood after the adoption of the slope paving solution. FIGURE 20 Wave damage on the downstream unprotected slope (TH-220 north of Oslo, Courtesy of Minnesota DOT). Issues related to the workability of paving slopes can limit the use of this technique in certain cases. Improper handling can affect the asphalt’s durability. Segregation and variation in density as a result of improper compaction can lead to faster crack development, which would lead to an increase in uplift potential. Nevertheless, this option is cost-effective in areas subject to slow or stagnant currents. To increase paving slopes’ durability, proper placement and adequate maintenance are important. Maintenance would include weed spraying and fog sealing (Lim and Anderson 2011). It is important to pave far down the slope, practically to the expected tailwater level. FIGURE 21 Placing pavement on the slope (TH-220 north of Oslo, Courtesy of Minnesota DOT). FIGURE 22 Wave damage after placing pavement on the downstream slope (TH-220 north of Oslo, Courtesy of Minnesota DOT). TH-1 East of Oslo During the 2011 spring flooding events, overtopping of this roadway embankment lasted for weeks. At the time of the overtopping, the downstream slopes were armored with a closed-cell articulate concrete block system. The system suc- ceeded in resisting the long-term overtopping. Prior to plac- ing the articulated concrete block system, a coarse gradation (OGAP) system was attempted but it failed in a previous 2011 flooding event. The two systems are discussed herein. Articulate Concrete Block System The system consists of blocks that are placed over a geo- textile blanket. Pavement or topsoil and turf are then

18 placed over the blocks. The system successfully with- stood the 2011 flooding forces. No damage to the down- stream slope or the pavement occurred. As shown in Figure 23, the newly installed topsoil was lost, and no turf was established at the time of the flood. Now that the turf is fully developed, it will likely perform better in future flooding events. FIGURE 23 Loss of topsoil in the 2011 event after the installation of articulated concrete blocks on the downstream slope (TH-1 east of Oslo, Courtesy of Minnesota DOT). The open-cell articulated concrete blocks were initially recommended from a design point of view. Yet the contrac- tor included pyramid solid/closed blocks in his bid, and eventually pyramid solid blocks were used. However, the spacing between the pyramid blocks did meet the criterion for open-cell system. Systems Prior to Articulate Concrete Blocks The downstream slope of TH-1 was initially designed as shown in the typical sections of Figures 24 and 25. Course gradation (OGAB) placed on top of a geotextile layer was used to enhance the resistance of the down- stream slopes against erosive forces. Yet the hydraulic forces exerted during the f lood far exceeded the granu- lar materials’ erosion resistance, and the system failed (Figure 26). FIGURE 24 Failing typical Section 1 in 2010 flood (Courtesy of Minnesota DOT). FIGURE 25 Failing typical Section 2 in 2010 flood (Courtesy of Minnesota DOT). FIGURE 26 Overtopping damage in 2009 flood (TH-1 east of Oslo, Courtesy of Minnesota DOT). TH-9 South of Ada In 2009, the TH-9 embankment was overtopped for a few days during flooding. This embankment is characterized by relatively flatter slopes; as a result, the velocities associ- ated with overtopping were relatively low. Figure 27 shows the damage inflicted on the downstream slope. Riprap was adopted as a protection measure and placed on the down- stream slope of the embankment (Figure 28). The riprap was then buried under an asphalt layer owing to such safety con- cerns as cars and snowmobiles accidentally running off the roads and hitting the riprap. The embankment resisted the 2011 flooding without any damage to the downstream slope or the pavement, as shown in Figure 28.

19 FIGURE 27 Overtopping damage in 2009 flood (TH-9 south of Ada, Courtesy of Minnesota DOT). FIGURE 28 Installation of riprap placed over geotextile and then paved over (TH-9 south of Ada, Courtesy of Minnesota DOT). FIGURE 29 Successful performance of installed riprap system and pavement placed over it post-2011 flood (TH-9 south of Ada, Courtesy of Minnesota DOT). Also shown in Figure 28, riprap was used to protect the downstream slope against anticipated overtopping. The rip- rap was then buried under an asphalt layer owing to safety concerns. Such concerns include cars accidentally running off the roads and snowmobiles. The embankment endured the 2011 flooding forces without any damage to the down- stream slope or the pavement as revealed in Figure 29. TH-200 West of Ada This case presents a failure of the pavement applied to an embankment’s downstream slope to protect against overtop- ping. The 2009 flood caused partial erosion and pavement damage on the downstream slope. The asphalt pavement was used on the downstream slope and failed, as shown in Figure 30. Thus, this technique appears to perform well to protect against wave overtopping in rivers, but not for prolonged overtopping in which higher velocities would occur. FIGURE 30 Failed downstream slopes with asphalt pavement placed on them in 2009 flood (TH-200 west of Ada, Courtesy of Minnesota DOT). Articulated concrete blocks were then constructed over the downstream slope. The system’s performance, however, has not yet been tested in this location because overtopping has not occurred since 2010. Practical and Financial Considerations Paving a slope is more difficult than paving a flat surface. Construction challenges involve aggregate segregation and difficulties compacting the asphalt on a sloping surface. Such difficulties affect durability; therefore, sloped pavements tend to deteriorate and crack faster. As a result, they may perform poorly during flooding events because water may infiltrate the cracks and contribute to lifting the pavement. In this case, erosion protection will be limited. The case example implies that paved slopes are more effective in protecting against wave action than against overtopping erosion. In terms of cost, grass is the least expensive material option, but it is limited to relatively low flow velocities and associated low hydraulic shear stresses. Grass is effective as long as the applied hydraulic shear stress does not exceed the

20 critical shear strength of the grass cover; otherwise, the cover will fail and the underlying soil will be progressively eroded. Pavement is the next least costly solution. Articulated blocks and riprap (with underlying geosynthetic fabric) are good means of preventing overtopping damage, but they are more expensive means of protecting against overtopping than pavement. Table 3 shows prices for riprap and articulate concrete blocks based on two projects in Minnesota. TABLE 3 PRICES FOR RIPRAP AND ARTICULATE BLOCK SYSTEMS IN MINNESOTA Protection System Project Year In-place Price ($ per sq. yard) Comments Riprap 2012 27.10 Class 3, 12” nominal, 18” max, including geotextile fabric Articulated Block Mat 2011 57.65 Open cell type 2 including geotextile fabric Maintenance Considerations In flood-prone areas, efforts are made to seal thermal and reflective cracks before flooding events. If left unsealed, water can infiltrate the cracks and cause internal erosion. Once flooding occurs, limited access makes sealing the cracks difficult. Another consideration is the impact of saturation on pavement strength. The potential for embankment satu- ration is generally considered when the water height on the upstream slope reaches two-thirds the height of the embankment. The long-term effect of embankment satura- tion on the pavement placed over the embankment has not been directly observed, but the following example gives a clue. The northern Red River Valley area is predominantly agricultural. Spring planting creates a flurry of heavy equipment and trucks on roadway embankments that may not yet be fully recovered from saturation caused by high water in the spring. Some premature pavement deteriora- tion has been observed as a result of increased heavy trucks and equipment. DAMAGE IN CANYON ENVIRONMENTS, COLORADO These three Colorado case examples lie in an arid canyon environment. In each case, the damage was caused by the intense prolonged rain and high-velocity runoffs caused by the September 2013 storm event. The embankments in these cases are generally characterized by steep slopes (2:1 or 1:1 slopes). The slopes were generally unprotected, but the river changed its course abruptly during the storm and eroded the roadway embankment. SH-7 MP 26.90–27.68 In this case, the Middle St. Vrain Creek changed its course, which led to damage along SH-7. The high-velocity run- off (with debris) eroded the embankment toe. Eventually, stretches of the embankment were completely eroded. The damage was located at the outer arc of the meandering bends. The failures at measuring points (MPs) 26.90, 27.68, and 27.28 are shown in Figures 31, 32, and 33, respectively. FIGURE 31 SH-7 damage at MP 26.90 (Courtesy of Colorado DOT). Emergency repair work was performed, which included the placement of rock-fill embankments (considered more resistant to erosion) and riprap on the embankment slopes in the vicinity of the creek at specified locations. US-34 MP 75.05–76.73 The damage occurred along the stretch of US-34 that runs next to Big Thompson River. The high-velocity flows eroded the embankment at the outer curve of meandering bends in the vicinity of the embankment toe. The damage was aggravated at certain locations because of the presence of drainage elements. These elements included highway cul-

21 verts under the roadways that drain mountainside runoff into the river and private access bridges (private culverts) that connect the highway to the properties on the other side of the river. Along this stretch of highway, the access bridges were severely undersized for such extreme flow rates and created intense backwater. This backwater resulted in turbu- lent flows that washed out the embankment and completely destroyed the roadway as shown in Figures 34, 35, and 36 at MPs 75.05, 76.40, and 76.73, respectively, in the vicinity of private culverts along US-34. FIGURE 32 SH-7 damage at MP 27.68 (Courtesy of Colorado DOT). FIGURE 33 SH-7 damage at MP 27.28 (Courtesy of Colorado DOT). FIGURE 34 US-34 damage at MP 75.05 (Courtesy of Colorado DOT). FIGURE 35 US-34 damage at MP 76.40 (Courtesy of Colorado DOT). Temporary repair work included placing rockfill and rip- rap at certain locations. For the permanent repair design, the impact of the access bridge locations on the overall perfor- mance of the flow and roadway embankment are currently being assessed. It is undecided whether the culvert bridges will be rebuilt with special provisions or protections to mini-

22 mize damage, or whether in the event of flooding the culvert bridges will be considered sacrificial structures, to maintain roadway embankment stability. FIGURE 36 US-34 damage at MP 76.73 (Courtesy of Colorado DOT). US-36: 7.70–8.00 In this case, the damage occurred along a stretch of highway that had been subject to realignment. The narrow channel of the Little Thompson River caused high-velocity flows at MP 7.90–8.00 and the erosion proceeded laterally as the water level rose. The riverbed was essentially at the level of the bedrock, but the steep embankment slopes failed as a result of toe ero- sion (coupled with softening and the corresponding loss of strength from the extreme amounts of rain). Portions of the road were removed by the flow. A hydraulic jump occurred downstream as the water plunged straight downwards and caused severe erosion. Two factors are likely to have contributed to this erosion damage: (1) the realignment of a river when rivers typically tend to meander, and (2) the area’s geology (rock riverbed versus relatively finer embankment material). At MP 7.70, one lane of the road was eroded most likely because the embankment material in this area was more erodible (weak point). This led to the structural failure of the overlying pavement (Figure 37). At MP 7.80, the roadway shoulder was lost (Figure 38), probably from slope failure resulting from toe erosion coupled with embankment soften- ing during heavy rain. At MP 7.90, downstream from MP 7.80, several feet of the embankment shoulder were lost. At MP 8.00, a 60-ft drop in the riverbed developed owing to the hydrau- lic jump that formed at that location. The water plunged from the bedrock bottom into the relatively softer mate- rial (Figure 39). FIGURE 37 US-36 damage at MP 7.70 (Courtesy of Colorado DOT). FIGURE 38 US-36 damage at MP 7.80 (Courtesy of Colorado DOT).

23 FIGURE 39 US-36 damage at MP 8.00 (Courtesy of Colorado DOT). Funding Agency The repair work was funded by FHWA Emergency Relief (ER). One of the key features to achieving the repair work within the assigned time and budget was the constructive collaboration between the parties involved. When disasters strike, it is not a straightforward process to allocate the funds and identify the responsible agencies while preparing for the temporary design. This process went relatively smoothly as a result of all the projected efforts of the teams involved. FHWA issued a quick release of the funds so that the repair work could be started right away. Within about 10 days, the contractors started work on a num- ber of sites. Design Methodology The design approach included one-dimensional (1-D) and two-dimensional (2-D) hydraulic modeling to identify the potential high-risk sources. The actual peak flows in the 2013 flood were estimated at several locations, and a hydro- logical study was carried out. The revised 100-year floods were calculated accordingly and will be used in the perma- nent design. Discussion of Potential Protection Systems FHWA ER funds were allocated for emergency repair of the damage caused by the September 2013 storm event. Based on FHWA funding regulations, two phases of design and construction are carried out: the emergency repair and the permanent repair. The emergency repair phase restores the highway to its initial condition, which restores normal traffic flow and ensures that travelers can reach their destinations. The adopted solutions for this stage were rockfill embankments and riprap protection for certain areas. The permanent repair (currently under preparation) con- sidered the different viable solutions throughout the project’s lifetime. The relevant design would elaborate on the type and extent of protection adequate to mitigate the risks faced by the highway. In general, minimizing damage to roadway embankments from flooding is approached through either channel restoration to enhance the structure’s performance, or embankment alteration. If overtopping is foreseen, rock-fill can be used as embankment material because it is more resistant to erosion and easier to place. The following embankment protection options are discussed further: veg- etation, gabions, riprap, paved slopes, articulated concrete blocks, and walls. Because of Colorado’s arid climate, the use of vegeta- tion is limited in some areas. The arid climate has also led Colorado DOT away from using gabions, which is now noted in the state provisions. HEC-14 recommends against using gabions in arid climate owing to the rupture of the wires of the baskets. Riprap is used to protect some slopes. The use of geotextile under riprap, however, is dependent on the type of repair (emergency versus permanent). Geotextile is gen- erally used under riprap for permanent repairs, but not for temporary repairs. Paved slopes are generally not used, due to the arid climate that causes cracks in the pavement placed on the slopes. Articulated concrete blocks, on the other hand, could be an option especially because such systems can be applied on steep slopes (2:1 or 1:1). Also, as the slopes get steeper, building walls remains an option. Wall construction to protect roadway slopes has been used since 1976. Several walls were placed on rocks (found at shallow depths) at the base of the canyons. During the floods, the walls withstood the water forces and limited erosion. The use of walls does present two relevant concerns: scour at the bottom of the wall and erosion around or in the vicinity of the wall can occur, and, depending on the flood discharge, water might get behind the wall. When the bedrock is shallow, walls can be easily used; however, for sites in which rock cannot be found even at 40-ft depths, walls are more difficult to use. MD-24 DEER CREEK STREAM STABILIZATION, MARYLAND This section presents the stabilization of MD-24 Deer Creek Stream in Maryland based on the information obtained through the interview. The cause of damage, site charac- teristics, stabilization methods, and typical sections are included herein. Cause of Damage The roadway embankment runs parallel to the stream chan- nel. When the stream water level rose, the unprotected embankment slope was eroded. The damage to the embank- ment slope accumulated from a number of flood events,

24 which required a project to stabilize the embankment run- ning along the streamside. This project was funded by the state and by FHWA. Techniques Used An implicated stone wall (Figures 40 and 41) solution was adopted to protect the roadway embankment against ero- sion. The stones were selected based on a number of con- siderations to satisfy the requirements set by several parties including the community panel established for the pur- pose of this project and relevant environmental and federal regulations. FIGURE 40 Implicated stone wall schematic drawing (Courtesy of Maryland DOT). FIGURE 41 Implicated stone wall under construction (Courtesy of Maryland DOT). The cross sections varied depending on the characteris- tics of the subsurface bearing stratigraphy (soil/rock) and the available distance to the designed stone wall. Figure 42 shows a typical retaining wall section and Figure 43 presents a reinforced wall section. FIGURE 42 Typical retaining wall section—spread footing (Courtesy of Maryland DOT). FIGURE 43 Reinforced slope section (Courtesy of Maryland DOT). KIMSEY RUN PROJECT, WEST VIRGINIA The Kimsey Run Project presents a case in which a stream jumped out of its course during a flooding event and over- topped a nearby embankment. Two flooding events caused embankment damage; thus, repair work was carried out twice: after Hurricane Isabel in 2003 and about 10 years later. After the first flooding event, the stream was shifted back and stabilized. After the second flood, the river chan- nel was reconstructed. In both cases, the repair work was carried out using state funds. The causes of damage and the techniques used in the stream stabilization are presented herein. Cause of Damage The roadway embankment initially lay in the vicinity of a river meander. During Hurricane Isabel in 2003, the river jumped out of its initial course at the location of the meander bend. As a result, the neighboring embankment was overtopped. The resulting damage included erosion of the embank- ment slope facing the stream as the water rose to the embank- ment toe (Figure 44) and pavement rafting (Figure 45). Little damage was inflicted on the other embankment slope, which was much flatter.

25 FIGURE 44 Slope erosion and pavement undermining after Hurricane Isabel in 2003 (Courtesy of WVDOT). FIGURE 45 Pavement rafting after Hurricane Isabel in 2003 (Courtesy of WVDOT). Although not verified, another factor that could have affected the stream stability was the pond that was built just downstream of the site location. This pond was built by NRCS (National Resources Conservation Service) to reduce the flooding discharge downstream. Techniques Used After the First Flood After Hurricane Isabel in 2003, surveying work was first car- ried out to map the area and its components. The river chan- nel was relocated and reconstructed further away from the roadway embankment. In-stream structures, namely cross vanes and rock vanes, were used in the channel to divert the water away from the embankment and to decrease the stream velocities at the bend location. Additionally, hardwood trees that were lost during the storms were used along the channel to strengthen the channel bank. A photograph of the com- pleted system is shown in Figure 46. This protection system functioned well for about 9 years. After that, the stream got behind the established bank protection and started to erode the bank slopes near the roadway embankment (Figure 47). This led to further reconstruction of the channel. FIGURE 46 Channel reconstruction after Hurricane Isabel in 2003 (Courtesy of WVDOT). FIGURE 47 Erosion at the bend location (Courtesy of WVDOT). Based on this project, in-stream structures worked for a while, but they were not a sustainable solution. The rocks were embedded deep enough in the stream bed to remain sta- ble. But as the water level rose, the water would go over and around the structures and eventually reach the embankments. A possible solution might have been to further increase the length of the rock veins across the flood area. The use of the tree trunks, which were supposed to strengthen the bank, resulted in more erosion around those obstructions. The effectiveness of this technique might be related to how deep the trunks are embedded in the bank. Based on this proj- ect, this solution would need further development since, instead of strengthening the stream bank, it caused more local erosion. Techniques Used After the Second Flood The second repair work included armoring the bank with larger riprap, as shown in Figure 48. No geotextile was used

26 for this purpose. The underlying materials were mostly cobbles that were considered good filter material. So far, the riprap has worked, but is not necessarily ultimately effective. In the future, protection of the embankment slopes would probably be considered as an option. FIGURE 48 Repairing bank with riprap (Courtesy of WVDOT). SUMMARY This chapter presented several case examples. It summa- rized the causes of damage and the techniques used (Table 4). The causes of damage varied among these cases, as did the protection techniques used. The direct causes of damage included wave action, overtopping, overtopping from waves, and channel migration. The repair techniques included articulated concrete blocks, gabions, riprap, stone walls, in- stream structures, vegetation, paving of slopes, and reloca- tion of streams. Based on these case examples, the success of the protection measures is found to be site and case specific. TABLE 4 SUMMARY OF THE CASE STUDIES Case Study Description Repair Techniques Used Evaluation of Techniques State Route 30 (US-98), Florida Significant damage due to coastal wave action Seaward slope protected using sheet piling, soldier piles, articulate concrete blocks, and assorted asphalt and performance turf Damage from subsequent storm was limited to loss of topsoil and turf reinforcement Childs Draw, Cheyenne, Wyoming Embankment designed for overtopping Downstream slope protected with gabions No damage Sand Draw Highway 48, Wyoming Overtopping due to undersized culvert or blockage of culvert with ice jam Additional culvert installed Site has not experienced overtopping in 30 years Unnamed Draw Highway 136, Wyoming Overtopping due to severe flooding or undersized culvert Downstream slope protected with gabions No damage Rock Creek, Wyoming Overtopping due to dam breach Gabions proposed to protect downstream slope _ TH-220 North of Oslo, Minnesota Overtopping by waves Downstream slope paved Minimal damage TH-1 East of Oslo, Minnesota Overtopping by floods in 2009 (Trial 1) and 2011 (Trial 2) Trial 1: Employed coarse gradation on downslope (OGAP) Trial 2: Used articulate concrete blocks Trial 1: Failure Trial 2: Loss of newly installed topsoil TH-9 South of Ada, Minnesota Overtopping Paved-over riprap placed on the down- stream slope No damage TH-200 West of Ada, Minnesota Overtopping Trial 1: Paved downstream slope Trial 2: Used articulate concrete blocks Trial 1: Damage to downstream slope Trial 2: No overtopping yet SH-7 MP 26.90-27.68, Colorado Severe erosion of the embankment riverside slope Aggravated erosion at relatively weaker locations and at culvert locations; slope failures due to saturation Emergency repair: Rockfill embankments and riprap placed on selected locations on the riverside slope Under study US-34 MP 75.05-76.7, Colorado US-36: 7.70-8.00, Colorado MD-24 Deer Creek Stream Stabilization, Maryland Accumulated erosion of the embank- ment riverside slope from a number of flooding events Implicated stone wall coupled with rein- forced slopes installed Under construction Kimsey Run Project, West Virginia Embankment damage due to stream changing its course in two flooding events Trial 1: Bank relocated and reconstructed using in-stream structures and tree trunks Trial 2: Bank armored with riprap Trial 1: Lasted for about 10 years Trial 2: No damage so far