[From the U.S. Government Printing Office, www.gpo.gov]
.~~~~ ~~~O ~~~~ >~~~~~~~l ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ vl N V '~~~~~~~~~~~~~~~~~~~~~~\ '~~~~~~~~~~~~~W N~~~~~~~~~~\ TD~~~~ 665 ~~L3 1982~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~V 2234 SL SERVICES CENTER LAnD Kff1 UnOrf (ONTtOL CHARLESTON SC 29405-2413 a guidance publication of the Waccamaw Regional Planning and Development Council "O�PertY of CeC a t I 1 - C9 ~Z' p O~~:CZ Waccamaw Regional Planning and Development Council Leslie Mclver, Chairman Kenneth C. "Ken" Thompson, Executive Director William J. "Bill" Schwartzkopf, Director of Planning Larry Schwartz, Project Director City of Myrtle Beach Erick B. Ficken, Mayor Carey F. Smith, City Manager Wilson Cain, Councillor Ted Collins, Councillor H.E. Pearce, Councillor Marjorie Stonebrook, Councillor E.A Thomas, Councillor James F. Futrell, Councillor Roy Mann Associates, Inc. Landscape Architects and Environmental Planners Museum Wharf Boston, Massachusetts The preparation of this report was made possible through a grant from -- the U.S. Environmental Protection Agency under Section 208 of the Federal Water Pollution Control Act of 1972, as Amended (Public Law 92-500) April, 1982 contents Introduction 1 4 What the Property Owner Can Do 30 The growth of Myrtle Beach as a resort city Introduction The Myrtle Beach urban stormwater runoff control study Permeable pavings Improved grading U 1 The Influence of Nature and Man on Beach Infiltration structures and Water Quality Median strips The influence of coastal topography on storm runoff Roadside drainageways * ~~~~~~~~~~~~~~~~~~~~~~~~~~Perimeter ditches dune encroachment, surface runoff, and beach damage Deter ds Detention ponds Taking stock of the beachfront: classification and analysis Landscaping Fold-out map: Beach analysis Locating pools, patios, and parking at a safe setback Mounding 2 A Strategy for Oceanfront Revitalization 16 Swales Four Zones: Defending against runoff erosion and water Controlled roof drainage quality degradation Dune walkover structures Design objectives for a low-cost beach Revetments, seawalls, bulkheads, and improvement program acceptable alternatives Fold-out map: Unified concept plan 3 What the Public Can Do 22 Introduction Conclusions Street end resurfacing and redevelopment Parking facility relocation For Further Assistance 42 Street storm drain system improvements Park development and public access Fold-out map: Public access Beach scraping and maintenance Acknowledgements and Credits 43 Dune and swale reconstruction and maintenance Dune walk-over structures introduction The City of Myrtle Beach, located in Horry County, South I Carolina, is one of the most popular resort cities of the Atlantic coast. Its wide quartz sand beaches, sunny climate, family- ; : id + oriented amusements, golf courses, moderate hotel room rates, and ease of access by automobile from eastern and midwestern states have sustained the city's attractiveness over the years. Together with these positive qualities and the continuing i- .. l, 4 A growth of the greater Myrtle Beach region today, however, U stand several problems that threaten to undermine the ap- ~'~-~ ,~ b Adpeal of the city's central, older beaches: erosion by the sea, overbuilding within the dune zone, the aesthetic impair- ment brought on by the construction of seawalls and bulk- heads to protect beachside buildings from sea erosion, and erosion and pollution from urban stormwater runoff, a which typically cascades onto the beach from the ends of storm drains, gullying the beach and degrading its quality. The purpose of this report is to suggest measures that may be easily undertaken by both public and private owners in Myrtle Beach to deal with the last-mentioned issue: erosion of the beach by urban stormwater runoff. The report also describes measures that can be applied to the problems of beach ero- sion by the sea and of dune zone overbuilding and seawall construction, although these latter issues lie outside the main area of the guidebook and are more fully addressed else- where. A list of titles for recommended reading and contacts for further assistance on all three areas of concern are given on the end papers of this guidebook. The reader is encouraged to review and consider the mea- sures presented on the following pages. Before actual con- a struction of any recommended technique, the owner should obtain the assistance of a registered landscape architect or site engineer and apply for any required permits. the growth of myrtle beach as a resort city Myrtle Beach, situated on the "Grand Strand" of northern South Carolina, has been popular oas a resort city ever since guest houses and hotels were erected to accommo- date summering vacationers in the early part of the twenti- eth century. At that time, most of the land on which the city stands was in the ownership of Myrtle Beach Farms and the first visitor accommodations enjoyed a distinctly rural flavor. Houses and inns were of one or two stories, widely spaced along the beach, and set respectfully back of the low dunes that stretched up and down the coast. Walks to the wide beach passed fragrant back-dune thickets of the wax myrtle for which the city is named. Many homes and inns had wood plank walks and dune cross-overs to allow tant as protectors of the backshore properties as well as at- - tractive features in their own right. Many walks had gazebos or other kinds of seating structures astride them at the dune crest. Some of these structures persist today in the older areas of Myrtle Beach and several modern day motels have built sun shelters in this old style. During the 1950's Myrtle Beach grew rapidly, accommodat- ing the post-war desire for vacationing and offering a medley of amusements and entertainment that complemented the beach as attractions for families with children of all ages. In � the 1960s and 1970s, the city grew yet further as the develop- ment of the nation's interstate highway system, economic air travel, Myrtle Beach golf courses and winter golfing, and other factors created good conditions for hotel construction and expansion. In the surge of growth, the old beneficial relationships between buildings and the beach-dune vegetation system y were ignored. Dunes and their mantles of stabilizing vegeta- . tion, including the back-dune myrtle, were leveled to make way for patios, swimming pools, parking lots. Some buildings were built on the dune line itself. To protect the new hotels and their outdoor features, seawalls and bulkheads began to 9:," ' spring up, since the old dune system that had performed the-V, same role previously was now gone where new construction - encroached on the beach. To drain rainfall from the pave- , ; ments and other hard surfaces of the motels, drainpipes were installed, leading to the beach itself. With the series of assaults from the sea that have oc- curred over the last decade, including Hurricanes David and Frederick, and winter storms, some beach has been lost and several seaside structures, including seawalls, I bulkheads, and parking lots, have been damaged as the result of increased exposure to storm waves. The urban storm runoff, too, has done its part to erode the beach and | leave pools of polluted water beneath the drain outlets. Recently, however, the city of Myrtle Beach has taken steps to ensure better protection of the beach and more effec- tive measures to deal with erosion through the adoption of zoning and ordinances to control development. Will the private owners, though, do their share to remedy the damage to water quality and the physical condition of the beach and dunes? Fortunately, many beachfront owners have expressed a willingness to take action, in pursuit of the finer quality beach landscape on which the city's tourism industry is de- pendent to a large degree. This report has been prepared to help them be of help. the myrtle beach urban storwater runoff control study The first comprehensive studies of the stormwater runoff prob- lem in Myrtle Beach were the 1978 Waccamaw Regional 208 Areawide Water Quality Management Plan* that was con- ducted under a grant by the Environmental Protection Agency. This area was later designated as one of the "Nation- wide Urban Runoff Program Demonstration Areas." These U studies identified surf water quality impairment resulting from stormwater runoff, and the 1980 Final Evaluation of Storm- water Runoff Control Alternatives. * The latter study examined both "structural" and "non-structural" control alternative solu- I approaches that would employ the construction of conduits to contain and carry runoff to outlet points other than the U beach and foreshore, were stormwater discharge to the Intra- * See Suggested Reading List I coastal Waterway, control of flow in Withers Swash, and This report is a follow-up to the final Evaluation report's exami- ocean discharge. nation of non-structural alternatives. The extent that property Beas*ftecs fsc ontuto,$0t 5 ilo owners can undertake the measures recommended here will any progress in controlling runoff through non-structural alter'-eemn hte oe ral ftecsl xedtrso natives would constitute savings in capital expenditures to the the structural alternatives can be avoided. But there are other C ity of Myrtle Beach. Among the non-structural alternatives advantages as well. The greater use of landscaped features, * studied were source controls, such as the use of porous pave- the avoidance of bulkheads along the beach and their pos- men, wichpermits infiltration of rainfall into the soil to reduce sible replacement one day with man-made dunes, and the ruof nlminatinocubadgter, which prisremoval of the myriad drainpipes that clutter and blight the stetrunoff to be shed into grassed and other earth or sand tebeach toa anprduc backshrea landsthetic improvement ina areas. In addition, on-site detention techniques were studied. tebahadbcsoelnsae nipoeetta * These included such alternatives as detention ponds, land- would have great potential value to Myrtle Beach's tourism * scape design, infiltration trenches, and dry wells, all having and vacation industry. the potential to detain runoff. ~~~~~~~~~4 I I I I I 'N' 4N'N 'N" I a I NN 'N'N<* ""4 N ' ('>4' "'.4"" N A' '' I \ .Nt \NN V<N N "9 'k >('>4 I 'N N, "'NN' 44' 1 N N nto, it ' 2 the influence of nature and man on beach and water quality the influence of coastal topography on storm runoff Because of low topography and frequently occurring water- are carried from streets and parking areas. The sand flushed ways that break through the beach ridges at right angles to from the beach through gully erosion ends up, in part, lost to the sea, municipal storm drains and other man-made systems the longshore currents that carry the drifting materials to other in much of Myrtle Beach carry runoff inland to Withers Swash, portions of the coast. the Atlantic Intracoastal Waterway (AIW), or other backshore Draining storm runoff inland to Withers Swash and the AIW is .aterways, .hile .treet .nd private storm drains onDraining storm runoff inland to Withers Swash and the AIW is waterways, while street and private storm drains on the not without its own problems. Since natural gradients, or the narrow ocean-fronting slope of the strand carry runoff directly grad t o he seaward through the mouths of numerous culverts and drain- slope of the land, are so shallow, it is difficult to move large seiawars ontoug the moutbeach iofnumerousculvtsandelfdrai- quantities of rain water quickly and effectively to waterways pipes onto the beach itself. through storm drains, swales, and ditches. It is the latter pattern that creates the ugly and damaging gullying of the beach face of Myrtle Beach during storms. In The extensiveness of paved and other impervious surfaces- gu llying of th e beach face of Myrtle Beach during storms. In streets, parking lots, rooftops - forces large quantities of i three and a half miles of central Myrtle Beach, 151 drains dis- water that would otherwise fall on the porous sands of the gorge runoff openly onto the beach today. The spouting Strand to shed into storm drain systems. Rainfall is thus carried runoff not only creates the gullies that last until the tides re- swiftly to he beach or to the backshor draingeways, with move their traces, but leaves pools of polluted water, collec- s tions of the litter, automotive leakages, and other matter that an intensity that is proportional to the intensity of the storm. WEainenLy that isBpropLt PiensiE s i I, ~, 1, I~ I ......... I - rIa rT 7 With continuing urban development in Myrtle Beach, the ex- erosion on the ocean side and the exceeding of drainage- tent of paved surfaces will grow, and with this growth the way capacities on the inland side could be alleviated. area of sands and soils left open and capable of absorbing There are ways to achieve greater infiltration and reduce rainfall will decrease. piped runoff. This report explains what they are and how pri- Unless counter-measures are taken to promote infiltration, yet vate owners and public agencies can take steps to imple- more runoff will occur and will tend to increase the intensity of ment them. The techniques recommended will not solve flow at beachface and backshore outlet points. flooding and erosion problems associated with major storms * ~~~~~~~~~~~~~~~~~~but can be effective in dealing with the frequently occurring If ways could be found to increase infiltration of rainfall into but and effecte inengith the, frement the andsand oil nd tereb redce te amunt f ruoffrainfalls of light and moderate inensity, and this improvement the sands and soil and thereby reduce the amount of runoff aoecudaheeavsl mrvdiaefrMrl collected and moved across paved surfaces and through Beach. conduits, the problems of beach disfiguring, pollution, and :4~~77~~Xf77"_~ : - ,, Ii~i~;~!~iz ! !4":::: . -,. OF" dune encroachment, surface runoff, and beach damage problems Beach erosion at Myrtle Beach is the result of a complex of A... _>... .... , ,, �v+| ft<x ae.~.~ ......................... factors: long-term geological processes (the high-water mark c~...."'~. - _ i=! � ._____has been moving inland generally on this section of the ' ,i".4 l | Icoast), the nearshore bottom patterns that refract (divert and C concentrate the energies of) incoming waves, the direction, intensity, and duration of on-shore storms, and other causes. Not the least of these other causes is the erosion caused by ....., .. urban storm runoff and the actual displacement of sand .....~~~~~ !..:E . dunes by urban construction. ",, Do*'-4"'e~ bdune encroachment * building, patio, pool, and parking construction When hotels or other urban development encroach on the dune ridge that lies at the back of the beach, not only is the natural protection afforded by the dunes removed, but a por- -,'~ ~ ~tion of the sand supply needed for natural renourishment of the beach is lost. Without the sand supply of the dunes, which provide sand to the beach when damaged by storms, the beach must rely alone on sand transported in from nearshore berms and terraces during the spring and summer "beach build-up" season. (The storm-damaged dunes are themselves rebuilt effectively only if a sufficiently broad beach can offer .-~,~,,~- ~ --reg- *.ioP sand driven by winds from the beach to the dune scarp, or v-r ~L, d-- rO VatN , front edge.) * seawalls and bulkheads I .. , These protective structures themselves encroach on the ~x. dunes as well as on the beach face itself. Although sand may ir '�~be backfilled directly behind them, it is really cut off from the "sand budget" on which the dynamics of beach and dune rebuilding relies. Seawalls and bulkheads are also aesthetically a problem. I I- . E..PL.EP~ $; Many beach visitors consider them a detriment rather than a ~.~.~�=rBYv f3J~.t ace> contribution to the beach experience. This poor image is - 1.O.~~- Ha- � e worsened when seawalls and bulkheads are damaged by storms or crack because of undercutting and settlement problems. o beach damage ~iS 6- T-�4~~6 I As a result of the drainage and impervious surface problems A11A1 5fl~F F,,zg~ described above, significant amounts of runoff are stopped from infiltrating into the ground and are forced to shed off I through street storm drains and private property drainpipes onto the beach itself. Gullying and stagnant pools result. In 1~-40FJ addition, where runoff sheets over uncurbed surfaces to the T9MAI * beach line, the flow of water leads to erosion of the top edge .~A~LI4 * of the built surface or the lawn edge. Where seawalls and . '~~~ bulkheads are built, not only is sand lost from the sand budget - * during construction, but the hard vertical surfaces of the walls - . and bulkheads create an effect that is known as "wave - reflection," a process that drives even more sand outward to sea. To provide a clearer picture of these destructive pro- , cesses, the diagrams to the right are given. surf ace runoff *street and walkway runoff IOcean Boulevard, the street ends between the Boulevard and the beach, and in some areas, street sections to the west of the Boulevard, all shed water towards the sea. Together wth the rainfall running off of walkways and sidewalks, a con- " I ieal amount of runoff is collected in the public right-of- way during rainfalls of even moderate intensity and duration. Much of this runoff is discharged to the beach through street oerflow drains. Since the water quality of this effluent is gen- erally poor (litter, automotive, leakages, etc.), the quality of ~~~ swimming conditions is also degraded. Pools of discharged Irunoff that remain beneath the outlets of drainpipes also scar the beach's appearance and environmental quality. I ,parking area runoff Parking areas of the hotels and motels fronting the ocean dis- Icharge runoff directly to the beach. Many parking areas on the second row and on some of the west-east avenues dis- charge runoff to Ocean Boulevard, which of course ends up on the beach as well. In a few instances, large parking areas on Kings Highway also shed water towards the beach. The same pollutants are found in parking areas as are found on ~ ~ i ; ' i,~*~,~ ,street surfaces - parking area discharge can adversely af- fect beach quality. � roof runoff a~ ', Although the roof of any one building along the beach col- ~aas~~~~~~~~ **~~~~ ~ ~ -lects only a relatively modest amount of rainfall, compared to o~:~~~~~~~~~~~~~ ~~the total rainfall of a given property, the total runoff from the roofs of the several buildings adjoining the common parking area or street end to which they discharge may be a signifi- cant contributor to the intensity and impact of runoff dis- charge. If the rate at which roof runoff is discharged to the roof drain, and the speed at which water emerging from the bottom of the drainpipe reaches the beach could both be re- duced, the intensity of runoff during the first critical moments of a storm might be also reduced as a result. Ways to manage roof discharge (delay ring, dry wells, infiltration trenches) are discussed in the "What the Property Owner Can Do" section of this report. ' lawn runoff Although lawns and other planted areas are the principal sur- faces within the developed lands of the city into which rainfall may infiltrate and thereby migrate more slowly to the sea, some lawns have been planted on imported soils high in clay content and are much less permeable to rainfall than are the natural sands of the area. In many instances, gumbo, a thick clayey soil, has been brought in to replace or cover the sand of the dune ridge fronting the hotels, in part to attempt to sta- ,,~~~iK~~~~~~ **'V"- ~'-" w'bilize the altered sand surface and in part to provide a plan- ting medium retentive of more moisture, to minimize lawn irri- gation. Unfortunately, rainfall sheds Qff the surface of a gumbo lawn almost as readily as it does from a street. Also, since dune grasses, such as Sea Oats or Switch Grass, avoid gumbo or other clayey soils, gumbo lawn edges exposed to storm waves at the dune scarp line have no thick fabric of the ON''~ TM ~ ~~~dune grass roots that effectively stabilize dunes elsewhere. With the onslaught of storm waves, exposed gumbo edges are easily disintegrated. 11~~~~~~~~~~~~~~~~~~~ I taking stock of the beachfront: classification and analysis I How significant to the environment and welfare of the beach 0 Analysis: Given the location and extent of the beachfront Where seawalls or bulkheads exist, there is little likelihood that beach face conditions and dune edge of Myrtle Beach is the double mischief of ero- classes, it is possible to begin to estimate the practicability of dunes can be restored, although if allowed by altered condi- sion by stormwater runoff and erosion by the sea? restoring remnant dunes, protecting existing stable dunes, tions such as an increase in beach width or the failure of the Thea h e s variable n width, slope, erosion rate, _ , ,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Tebahfc svral i itsoe rso ae *Would it be possible to undertake remedies to either or both and constructing new dunes as measures for restraining and walls under storm attack some restoration may be possible. nershore sand supply, and other factors that determine of thesbe problems? toud aermdetoihrorbhabsorbing storm runoff. But other factors described here shed probable future erosion (or accretion) of the beach section of further lightponrwhetherothisblemsac may be practicable * and also help determine the relative feasibility of dune To determine the answer to these questions, surveys of beach, furand wher light on whether this approbeach it may be praeffecticable land use behind the edge and swale reconstruction, on a site by site basis. * ~~~~~~~~~~~~~~~~and where on the beach it may be effective. nearshore, and backshore conditions were undertaken in Of the conditions identified, lawn or other landscaped areas 0 Analysis: With modest beach renourishment in selected 1980. Conditions affecting sea erosion and the potential edge condition and natural areas constitute a minor portion and parking and areas, accomplished by inexpensive means such as measures that might be adopted to affect it were studied by Thr ee onditions ar typical, although others exist, on the othe hard, impervious surfaces cover the major portion of the mechaniz ed scraping or e h Research Planning Institute in 1981. Conditions resulting from eds f devele nershof deposits, the profile oth stormwater runoff, encroachment of urban development on el d a n periou re of te a beach face may be rai, the dunes and beach, and the potential measures that might * Seawall or bulkhead Analysis: The land and impervious surfaces of streets and dunes/sw ales reconstruced be adopted to improve runoff control and the beachfront * umbo embankment (ordinarily planted with lawn prvts f storm r n to he ba Unes the area a a ne c tc landscape in general were studied in 1980 and 1981 by Roy amounts of storm runoff to the beach. Unlssese areas are For an in-depth identification and analysis of beachface Mann Associates. Data on storm drains, water quality, and grasses) resurfaced with porous paving and other surfacing systems conditions and recommended beach treatment mea- * runoff control were provided by Moore, Gardner & Associ- 0 Sand berms (man-made and not stabilized with dune that allow substantial infiltration of runoff, pipe discharges to sures, see selected references identified at the end of this ates, Inc. The results of these surveys are presented on the fol- grasses) the beach will continue. Unless, in new hotel construction or guidebook. lowing fold-out map and include a number of key In addition, some rip-rap or rubble stone revetments have reconstruction, hard patios pools, and parking are not Recommended measures with defined locations are * observations. been installed in lieu of bulkheads by beach property owners. located at a sufficient setback from the historic dune line, given in the fold-out map Unified Concept Plan Dune fencing is another edge condition feature, installed creation of duna e arunoff absorpon systems will not beachfront classes between private lawns and public dunes. be possible at these locations Six types, or classes, of beachfront can be defined at Myrtle * Analysis: Gumbo and other earth embankments are the Beach, reflecting the impacts of land use on the historic dune edges most amenable to change. If these could be altered to stormwater ouffall ridge. provide a reconstructed dune to intercept and absorb sur- The locations of exposed pipe ends, length of exposure e Class l: stable dune and back swale; insignificant face stormwater runoff and a low swale behind the dune to the severity of erosion at the pipe's point of emergence, disturb ance. a llow excess intercepted runoff to settle and be absorbed by andthelocation of standing wate were udged as having Class2: dune remnants; back swale filled with soft wider area, most or all of pipe discharge to heavy bacteria counts in 1980 and are indicated on the classn2: dune remnants; back swape filled wthsoft the beach might be eliminated. See the "What the Property landscape Owner Can Do" section for installation of Dutch drains as over- p * Class3: dune remnants; back swale filled with hard flow devices. Where sand berms adjoin lawn-surfaced 0 Analysis: The reliance on piped discharge of runoff is so *I~ ~ surfaces property edges, conditions may be even riper for application extensive in Myrtle Beach that a shift to reliance on greater Class 4: dune and swe non-existent; minor seawa or of this measure, if the berms are suitable for development into infiltration and absorption of runoff in the zones behind the * Clas4:bulkheadn swenxub stantial m ioad e berms adunes. (Note that the "dunes" referred to in this report as re- beach would be possible only with concerted public and On the fold-out map that appears on the foowing doube spread a cassifi- bulkhead; substantial made berms cation and analysis of conditions that existed on the deveiopment edge of 0~ Cls uean nneiset ajrsawl rconstructions cannot be considered equal to the historic private effort and cooperation. Careful evaluation must Myrtle Beach in 1980 the year of the sre e eenede O Class 5: dune and swale non-existe n t ; m a j o r s eaw all or~~~~~~~~~~~~~~~~~~~~~~~~~~~~Bah n 98, h yarofte urey aeprsete. h mp ils Class 5: dune and swe non-existent major sewll or dunes of the beach ridge, which were part of a natural sys- also be given to such possible measures as a municipal trates the severity of displacement of dunes by parking lots pools and patios bulkhead; minor made berms tem that is now missing, for the most part, in Myrtle Beach. marginal conduit collection and pumping system and as well as the frequency of exposedpipeendsandthewaterqualityimpair- merit features evident on the beach. In addition, the potentiai of individual * Class 6: dune and swale non-existent; major seawall or However, even though artificially created, they would re- controlled overflow outlets as supplements to a system that beach segments for dune restoration atre noted. Beach conditions werte sur- bulkhead; no berms; large pipes exposed. semble true dunes - and so the use of the term is justified.) relies on infiltration and absorption. veyed in 1981. 12 13 2 4 2F4 3 2 352 3 2 354531 2 3 2 3 23 2 31 3 24 a 3r4P5L4L 4 5 L . I p..: LSL P~~SP SiP SL P L g p PNI L FS] P s F S isP P LS P S HPJ L I-PPS]F75'S SPL L H P1nae P -5 Is IsIPIS!, �"' [~~SS rs ::j'P;: T[:ssl sL HPpy~ II :Urp Atlantic Ocean MSL * - . - -I---.5 LI el OCE AN OI - BEACHFRONT CLASSES EDGE CONDITION LAND USE BEHIND EDGE STORMWATER OUTFALL ~~~ ~~~~~~~~~~~~io astheiarblem dne .... iI stable dune F dune nonexistent SeaWallor Bulkhead swale behind dune minor sea wall apparent * Pipe End: Moderate Beachfront I controlled pedestrian access (walk- 4 substantial man-made sand berms Parking ov le " I ~~~~~~~~~~~limited planting (soft) areasErso onestructures and dune fences) i a fpnembankment native vegetation minor aesthetic problem~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Pipe End: Severe Beachfront :::-::::iii::::i:::Sand Berms Other Hard Paved Surfaces dune remnants but dune protec - m uesannnxsetSn em PHadPvdSrae n:EteeySvr tion required rIEoso ti~~~r. rqu ire~~~~~~ dune/s:.ale nonexisten R Ppe End: Extremely Severe swa,, nonexist ent major sea walls or swimpool walls Beachfront Erosion landscaped (soft) treatment of minor man-made sand berminq ****mmm Existing Dune Fencing swale zone 5 moderate beachfront erosion Swimming Pool ) Toxic Standing Water Iimitdpdsra oto moderrate aesthetic p roblems ited pedestrian control moderate aestetic problemsBEACH FACE CONDITIONSource: RPI 1981 LinearLaee or Ex ped Are I j done a nos dent bt dune dune/swale nonexistent i restoration/protection required aLjneor et o Landscaped Area m swale non-existent man-made sand berms nonexistent 19 7 7 fait Sea Le hardurfaces/edges in swale zone Excellentwithout limited planting (soft) areas severe beachfront erosion [some renourishment - The 1977 "nan Sea Level ?v'L 0eac'e limited swanting softe sereas major aesthetic problems: rubble, is the contour indicated OI tr's -aC. 1no pedest rian control over dune. qarbaSe. broken De ends. tc. see the Unified Concept Plan 'c'-oA -a; Infeasible without major Natural in the conclusions secio guide- [3j Good, some problems L5J renourishment book for the plotted 1981 mSL beach'ine and a comparison of the two. W3 Fair, numerous problems I 3 2 3 2 s a a 5 3 5 3 5 3 5 ,Ili s 3 ~~~~~4 2 5 3 5 6 5 3 5 6 1, l~~~~c;~ ���������-��::::::::6 w-~~~~~ssi~lxs ~ ~ ~ ~�5 1 ~ 3 -4 2 5 35 6 5 3 5 3 12 34 3 2 3 2 5 6 6 __ 1 I ................iS 3arking L P N Unpaved Parking P L S1CtP fIT WpL T HP S L S P N P L PHP HP P HP L S P P P S P N -1 - ~__ Attantic Ocean 9 --4 3 -1 U -~_r LB --7 U i~~~~~~~~~~~~~~~~~tj1 - - (P~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~L~~~~~~~~~#-~~~~~~~~~~~~ c ~~~~~~~~~~~~~~~~4~~~~~~~~~4b -~S - 35-_1__~42 o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i ,,~ ~~~. L1 Tj BECFRN Section 5/Stormwater Runoff t Study Area Mrtle Beach, So C Waccamaw RegionlPanncn eeomn oni Roy Mann Associates, Iccnutn Museum Wharf, Boston, Maseahstt0 oO ~~~~~~~~~~~~~~~~~~~~~~~4~~~~~~~~~a i 3 I 0; c~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~010 0 0 I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~fi I~~orIIr 1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ItM a strategy for oceanfront revitalization the four zones of the city's beach: how i they can be used in defending against runoff erosion As we have seen, there are two major causes of erosion of the beach: storm-driven waves of the sea and storm zone 3 east drainage/absorption runoff from the land. We also know that although the sea zone 3 easszone 1 dunes can cause serious erosion, urban storm runoff also de- zone 2 swalelabsorption ' grades water quality and the aesthetic qualities of the ~r Am zone 0 beach beach. If we can control urban storm runoff, a good deal _- would be accomplished to restore the recreational, water quality, and visual character of the beach. At the same time, if the beach can be helped to withstand $ /tl. ...__ _.--. further narrowing by erosion from the sea, a good deal n. -2ew park '~ more could be accomplished from the recreational stand- point, not to speak of the added protection that could be beach access ~ afforded to property along the beach. realigned parking ,- rehabilitated dunes With these objectives in mind, we can see the broad belt rehAbilitated d unes along the sea as divided into four parallel zones, in each of which lie opportunities for private as well as public ac- tion to remedy erosion and water quality impairment. \ t increased landscaping iThese zones are called: . S S--~" -,'~ ; .....-- . � Zone 0 - the beach :,7 ...-: � A Zone 1 - the dune 0 Zone 2 - the swale Zone 3- managed absorption zone Let's examine each in turn, starting from the landmost side: The beach (Zone 0 of the coastal edge) is vulnerable to erosion from both the sea and stormwater runoff. The dune line (Zone 1) can hold back and zone 3 - the managed absorption zone absorb surface runoff unabsorbed by the swale. The swale (Zone 2) pro- vides for infiltration of runoff not absorbed by Zone 3 surfaces. Public and This zone can really be further subdivided into the area private parking areas, motels, street ends, and public walkways form the that slopes directly downwara to the beach, much of primary absorption zone (Zone 3]. Existing surfaces in this zone should be re- which lies to the east of Ocean Boulevard (which we can designed to incorporate porous materials for parking, drives, and walks, along with extensive landscaping to provide for positive absorption of call Zone 3/East) and the other areas of Myrtle Beach, stormwater. some of which drain indirectly to the beach over street sur- faces while others drain indirectly or directly to Withers Swash and elsewhere (which we can call Zone 3/West). 17 1 In Zone 3/West the opportunities for improvement lie in Where a high profile fails, a low swale - scooped out to an managing lands to absorb as much rainfall as possible on- elevation somewhat lower than the parking area and site, by substituting porous or other permeable paving for lower than the dune as well - can succeed in receiving hard surfaces, setting aside as much of a portion of the overflow runoff, before it reaches either a dune or an emer- property as possible as landscaping, and by other means gency overflow drain to the beach. Given a good, perme- that encourage infiltration of water into the subsoil and able surface - standard lawn on a sandy soil is ideal - prevent excess waters from reaching Zone 3/East, or reach- the swale can act to absorb and transmit to the subsoils ing the Intracoastal Waterway. and the underportions of the dune considerable amounts In Zone 3/East the opportunities for improvement include of runoff, the excess portions of which will migrate beneath the dunes to the beach "invisibly," without the gullying, all those that are applicable to Zone 3/West and, in addi- the dunes to the beach "invisibly," without the gullying, tion, a number of measures designed to make sure that scarring effects that the existing pipe systems cause. water shedding down the slope to the beach is slowed as much as possible, so that infiltration into the subsoil is given the best chance for success before runoff reaches the Here, with a more complete dune system (whether arti- swale zone. ficially reconstructed or natural), a number of things These measures include parking surface grading happen to strengthen the ways in which stormwater runoff designed with shallow "landings," or breaks in the down- is prevented from reaching the beach: ward pitch of the pavement, so that water can be slowed � Runoff impoundment. Excess water not absorbed by at these intervals and given a greater chance to infiltrate the back-slope swale will accumulate above the sur- through open pores of the porous paving or other perme- face of the swale, moving relatively slowly through the able paving used. Such techniques - explained in greater dune and spreading out through the sand structure. If detail under "What the Property Owner Can Do" - will existing drainpipes are removed, the movement of help slow and reduce the amount of runoff reaching Zone runoff to the beach will therefore be relatively slow 2/the Swale. and non-erosive. With emergency overflow trenches buried within the dune, some washing away of sand zone 2 - the swale on the beachside of the dune can be expected, but on the whole, runoff may be effectively controlled This line of defense is an important key in the battle to con- on th e whole, runoff may be effectively controlled trol urban stormwater runoff. In most areas of Myrtle Beach, through dune impoundment. there is no buffer between the lower end of parking and zone the beach other paved areas (Zone 3) and the beach (Zone 0) that zone 0- the beach can absorb or at least retard runoff flow. In locations where Here, with limited but effective beach scraping and a dunes still exist, the land in the lee of the dunes is raised higher, wider beach, several things will happen that can lawn or patios (designed high to afford lounging hotel aid in sustaining existing and restored dunes and berms patrons a better view of the ocean). The high profile allows and reduce erosion to the beach resulting from stormwater no runoff to collect, so that all overflow parking drainage runoff. must, under these conditions, be piped to the beach. 3 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~18 � Better protection of dunes from wave attack. The There, dune grasses and, where they are placed, higher, wider beach will tend to keep storm- gross and sand build-up compensate sand losses in-M generated waves and high tides further away from dune fences will trap the sand particles and help5 the dunes, allowing them to persist and be of value curred during storms and trampling by beach visitors. during the more infrequent storms of greater severity. 0The net result. The effect of the stronger clune-g Dunes that are relatively safe from the frequent nourishing brought about by beach scraping will beU nibbling away by the sea that is typical of the Myrtle beffer prtcto o f t h bcpgmsorwtrrn Beach dune line today provide a more hospitable en- off, which can be barred from pouring onto the vironment for dune gross growth, and with this growth, beach by the dunes. In addition, better protection ofU greater stabilization and strengthening of the dune. backshore property from wave attack from the sea * Greater sand supply. With a wider beach, more sand can be accomplished. will be picked up and carried by winds to the dunes. 19~~~~~~~K~K" design objectives for a low-cost beach improvement program the objectives I increasing infiltration � limited renourishment and maintenance of the beach To allow greater entry of rainfall into the ground, thereby To restore a higher and wider beach profile in areas of reducing the flow across surfaces to the beach, dimin- the beach that have been subjected to excessive ishing the intensity of flow impact, and reducing erosion. pollution. To provide a greater degree of protection for beach- front property and for the dunes from storm-driven waves. * impounding and decreasing runoff To provide a greater supply of beach sand from which To hold surface runoff in swales, ponds, and other winds can nourish the dunes. containments to reduce surface flow during peak To decrease or eliminate installation of seawalls and rainfall periods. other structures that weaken the resistance of the beach to erosion. e establishing a construction setback from the dune line To protect existing dunes and the high beach from en- croachment and destruction. To allow eventual construction of dunes and backdune swales as beach conditions allow. * restoring and maintaining dunes To allow both reconstructed and existing dunes, together with backdune swales, to act as an urban de- tention and absorption system and as a barrier to storm- driven waves. To improve the aesthetic quality of the beachscape by reinforcing the natural appearance of the backshore, while at the same time allowing possible removal, where conditions allow, of seawalls and bulkheads for which the dunes and swales may serve as a substitute, as well as removal of drainpipes. 20 U I I I I I I I U I I I 'xQ 4 " \k 3 N. t Street ends and public walks between Ocean Boulevard All redeveloped street end parking should be designed and the beach, the beach itself, most of the sand dune and developed together with private and/or public system (Zone 1), public parks, and the streets and public redevelopment in Zone3. -- ,parking facilities that serve the beach area are all impor- tant factors in the beach recovery story. Fortunately, they are all public property, and the City of 3' ""' ' ,Myrtle Beach is embarking on a vigorous program to con- parking facility relocation / , .j: . ,.~.~,~. trol urban storm runoff and restore a quality beach to its Parking facilities should ocean frontage. ciently away from the beach to avoid direct destruction, i* .- .' ,~i,~-=-- -.. --~-~_. 'The following techniques illustrate those steps that either stormwater runoff, and other impacts on dunes and the - - ~ -, ,�.J~l~---~r':'---~are being currently taken by the City, such as are beach, A setback of 1 .!_~ � ~,.,/~.~- '-,~ .... ', ,~ ~-.,.~'1~-described in a number of the dune reconstruction and I described in a number of the dune reconstruction and ~~~~~~~~~~~~~~~~~~~~Water should be voluntarily adopted by builders, unless I f k(a -o walkover design examples, or are recommended as addi- local ordinances require other conditions. New or relo- tional measures to help achieve greater rainfall infiltration cated parking could be: and runoff control on public property. and runoff�control on public property. * developed into open space associated with Additional measures, such as the development of ade- beachfront hotels[Zone 3). . . quate public parking capacities along Ocean Boulevard, * built as multi- or bi-level structures on the west side .1,4 ,/4,/z/l,' are recommended to help private owners pull back park- of Ocean Boulevard, which can help free the dune what t h e public can do . . . ing from existing sites at the dune line - an indirect step zone and beach edge from parking. towards allowing swale and dune reconstruction and the * developed on exi achievement of a quality beach landscape. Ocean Boulevard. street end resurfacing and redevelopment Stormwater control measures that, as detailed in the "What the Property Owner Can Do" section of the handbook, should be used to upgrade existing and proposed street end parking areas where feasible and on all proposed public and private on-grade parking facilities adjacent to the beach, Also, where runoff is in excess, drainage methods should tie into an improved street storm drainage system. The following proposed measures should be used. * permeable paving * improved grading On the fold-out map that opens atthe right, public parks, including proposed * infiltration structures street-end parks and other park areas, and an improved public access sys- tem are presented. All such improvements can be designed for high infiitra- � uncurbed median strips and landscaping tion, serving important roles in stormwater runoff management. 4 ~~~~~~~~~~~~~~-4 30tN 29th N 28hN 2t 6hN25th l2t 23rd N 22n 21s 20th N 19th1 N lath m 17th N 16th X 15th7 m lath N 1th N 12th N 11th R 0hN9h N8tN7hN Convention center 4, f IM~~~~~~~~~~~~ PUBLICLY OWNED LAND SPECIAL ACCESS FEATURES RECREATION AND OPEN SPACE FACILITIES___ EXISTING PROPOSED3 7 4State of South Carolina Titlem ~'" Mean High Water (City base, 1977) * Major Beach Access Points L~JParks L.JParks (sources: "Myrtle Beach Plan" Imagoe Beach in City Title 'RMA street-end plans") Property Line (City'base, 1977) -4 Linkages/ Beach and Key Recreation Facilities Fish Pier Boat Ramp(source: "Myrtle Beach Plan") W Street Ends Dune Walkover Dune Walkover fsource:'City of Myrtle Beach") WJ Public Walks3 -~~~~~~~~~~~~ �ZZ ~~~~~~~~~~~~~~~~~~~~~~~~~~- **......... LU ~~-11L' 13 iq 4th N 3rd N2nd N 2dS3d '4h)I i 7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~- ~~~o I~~~~t 5th S 6th S 7~~~~th S ath S OthS 10th S 11ithS 12th S 13th S 14th S 15th s l a th s 17th S 18th S 19hI PUBLIC ACS saettlo S/Stonnwater Runoff Control Study Anea Myrtle Beach, South Carolin Waccaraw Regional Plannin Boy Mann AssociateS, Inc., Consultant museu, Wharf, Boston, Massachusetts 5(h~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 10 200 600i ,,1 - dof street storm drain system improvements Obviously, it is in the best interests of the citizens of Myrtle The contributions to controlling stormwater runoff that both Beach to work to ach eve stormwater runoff management 3 ,,ii rehabit -_ -a t=ed dues public and private property owners make through increased d ................ fence measures, can have a beneficial effect on .........t s m . discussed here. If they cannot be achieved, the reliance on on-site infiltration, dune and swale reconstruction, and other ........... ' ....................,-~.~ ~:~: '~ .-' ~.' ,, . ~.~ - ~,' ?,,, ............ " more expensive solutions may be necessary. .............. -- ~ ;-'~'~, .,,.~,, ..... ~,~� ......~., ' ......... dune fence measures, can have a beneficial effect on street storm drain systems. With more runoff percolating downward at each site, park development an less water escapes parking lots, drives, and other hard surs --~ swal aifs In retards g ntr-off faces into the street system. Parks are public leisure grounds which are predominantly I--f'~' "~'~~~ > If enough effective on-site management is achieved; future free of structures and typically include lawns, gardens, expansion or enlargement of the municipal system may be and othe extens vely p anted areas. Having few mper- -[~~~- -- --' ~~~~~less extensive than would be the case if parking and other io aes, lti o rainfall w r - hard surfaces continue to be constructed of impermeable tve ease, depending o materials'~~~~ alone. ~~tions. Parks and other natural areas serve important func- Wh exMe* en= path I u r t o materials alone. tions, therefore, in helping to absorb runoff with: Ik-~od' ~'~" '- ~ alhretargr lr-offfrom If the problem of beach pipe runoff can be alleviated I repacire .hrra r- ac ,; ane zo through adoption of the design tools explained in this hand- * lawn areas Wil i dMscawd sa -- book, there is also a possibility that the need for costly inter- 0 shrub beds ceptors designed to divert stormwater runoff from reaching * play surfaces employing ungrouted aggregate the beach may be reduced. * walkways and other hard surfaces using permeable paving iv !iX / tt 9 * additional parking -pool 11 .W7=: < G i l 1 :..^g. .......... 'parking & pools relocated ~, .~ '0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~fo within setback line poro~ surface materials I1 ,r /, ..L~ ~ surface drainage1 ; 1 s mai / X/;t '"' "XEU'?C . :zone 3 I zonei2 zone i | zone 1 I I the four zone concept primary absorption dune Iswale beach I street end redesign concept for increased runoff control 24 25 Hurl Rocks Park and Chapin Park are two public parks in Myrtle Beach that work in this manner. The street ends and public walks of Myrtle Beach are also I potentially helpful in providing surfaces between develop- ing parcels that can serve as infiltration zones. They can do so with: � permeable paving * landscaped borders e grading that controls the velocity and direction of runoff so that infiltration is maximized. Any public access improvement program should consider the utilization of the above techniques so that runoff con- trol is enhanced at the same time that public access is improved. beach scraping and maintenance Beach scraping (bulldozing of sand from areas of the beach at or below the low tide mark) is a technique that can be employed to restore modest amounts of sand to the beach face or to the dune zone. Where used, this tech- nique can help improve the recreational quality of the beach and secure a sand supply on the upper part of the beach that, with the aid of on-shore winds, can help keep : dunes well shaped. Beach scraping and maintenance principles and recom- mendations can be found in consultants' reports on the subject listed in the References section of this handbook. IP BrtS.X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'',2 PLA.4d PEA 0A1'r /UTLF /, e F=ILf dune and swale reconstruction and maintenance I / / PP41O69-I PpoE Sand dunes can be reconstructed where beach width and rll :11 a __ :'i profile and other factors allow. - . -- r plate HUGE O Dune reconstruction can be accomplished by ..." -~- iF:r'' importing or bulldozing borrowed sand from the beach against the dune scarp or up to and over the U 3 ToF ap innsto7~U~ existing free standing seawall or bulkhead. After sand I placement, stabilization should be attained through dune grass establishment and dune fence I construction. dune reconstruction fronting seawall 0 Free standing seawalls and bulkheads can be incor- porated into dune reconstruction and can serve as P~ciu~--- ww-~- Ff4,B fortifying cores to improve this line of defense against U ' pca oa'_rs, the sea. -_ UT__C _'; . �* Sand berms can be constructed in front of seawalls "/ st / /t 3-- --ERLF~ and bulkheads and should follow the guidelines for dune reconstruction. Dune fencing, however, should be placed directly behind the berm crest within one m ..~ fII& �.--.i~ foot of the seawall or bulkhead, as well as at the berm toe. d0 'OF if�L�Ff �0 Vegetation suited to the beach environment should be used to stabilize dunes and collect windblown sand for dune construction and restoration. Sea Oats (Uniola paniculatum), Hatteras Beach Grass (Ammo- philas breviligulata "Hatteras'), and other suitable species can be used; however, professionals should -- �f aF.,F.. be consulted before planting to determine site spe- 3 / ss CT t - IR,- Fe-in cific suitability for particular species. /.,' X 7vLJ>> -�rST-S. 0 Dune fencing that is typically constructed of wire-tied / P/' JrE r'L-oV^Q vertical wood slats and secured every ten feet by | _,-r~. t�4 _~:-'r~ seven-foot steel stakes that are driven into the beach sand approximately four feet should be installed 7]< . .i. :' -- --behind the scarp toe and along the landward side of I the dune or sand berm. The fencing directly behind the scarp toe will encourage sand deposition that leads to dune formation and provides protection from 1 beach access together with the fencing along the dune fence sectionlelevation back side of the newly-formed or established dunes. 27 ~i- - A OFSLE * Back dune swales should be constructed in conjunc- tion with sand dunes at elevations calculated to allow ii a E urban runoff to collect and be absorbed. In areas ,. / / - _J 'P r%,O where permeable sandy soil exists, swales need only / / be properly graded and planted with lawn grasses. Where less permeable soils exist, such as gumbo and .. -_ others, removal or scarificatoin of these soils and ......... placement of an eighteen-inch minimum layer of sand is recommended in conjunction with vegetation establishment. swale and duge edge reconstruction * Maintenance of sand dunes, berms, and swales, whether existing or newly formed, should be per- - _ . . ..- _ ...ov um formed by installing dune fencing to prevent foot access over dunes and by planting dune vegetation so that positive stormwater control is assured. * Existing drain pipes that extend onto the beach . . ...I should be cut and capped in conjunction with dune .., --- Amr e, 'r swale reconstruction and maintenance at their inlet ,- ' / . '. side, and cut from the beach side and backfilled with .r -. ,; ,,F: beach sand so as not to become a physical and . - visual nuisance on the beach. dune maintenance dune walk-over structures Beach access and dune walk-over structures should be - -. L....,d-rr e-a' fAfF- used to facilitate beach entry from street ends and shore- i __ L front parks and other public access points. Such structures / _avow will protect dunes from trampling and sand loss. /"- --/ _ _,_p Hod * The design and placement of beach access struc- ___ A E4S PIp E tures should follow the requirements of locally ac- , , cepted engineering practices. t ,/ * Pressure-treated lumber and hot-dipped gal- vanized bolts, nuts, washers, nails, and other hard- ware should be used for all planking, platforms, and stair construction. � Secured wood planking constructed of two-by-six- inch lumber, separated by one-inch galvanized pipe spears, and held together by galvanized steel cable drainpipeabandonment OR ~*f~I-TIf* ~.A~,PE should be used where feasible to. provide confined /PStrurt, '.12z" beach access within back-dune zones. * Elevated walk-overs should be used to provide /d~~,~IL. ' 1t +t4;beach access over sand dunes and berms. Either boardwalks or wood plank paths can be used to pro- vide access to the walk-overs. Wood plank paths are less expensive and more aesthetically compatible 2 .L&H PPl& �FOLE |~tf;~L~Fij~i~i~il rthan raised boardwalks where clear visibility along i the backs of the dunes is critical. � Dutch drains dug directly into the ground and filled with shell hulls, gravel, or other highly permeable material that is separated from the soil by a filter mat, typical dune walkover can underlay porous walkways and thus accept and absorb runoff. The filter mat will prevent soil from clog- .e..... 'XlOMkT ging the pores of the coarser material. These Dutch TLPTC'lil adrains can also provide an emergency route for ex- cess runoff that has collected within back-dune /Soo~L- / ~-~-- rswales. Overflow would move into the trench and out through the dune base when water in swales reaches APUkAE f01V O4_o a certain level. These ditches can extend behind the a -,tl4 1er ,TAlIL dune scarp and be covered by dune grass or other appropriate cover if they are not used as beach ac- cess paths. extended stairs over dune 29 III lf~s~"Y~~Tn~s~evFI ______ what the property owner can do I ~~~~~~~~~~~~~~~~~~~Li The individual property owner can improve protection of beach area dwellings and other valuable structures on sites vulnerable to standing water and runoff impact 3 through a number of simple techniques, depending on the location, soils, slopes, and water table of the site. The property owner, at the same time the site is being im- I proved to enhance protection of valuable structures, can help neighbors andl the public at large by improving on- I site runoff management control, so that rainfall is not MINUE1`, T" 'po~L-, ,HAL-'LT simply shed off the property onto streets and, as is some- ,,_ _ .~ . -~8 'D 4" rFi ~ue- ,roHa-E times the case, down to the beach. ;q 53,kcc~c~O~ { nhtQ~ 9GJaE -U5L~Hc ,cC-rFt The following techniques demonstrate how stormwater ;IGIMIDLBIIInwIUI A Ln -~arunoff management on private property can be effectively ."r~t W 1 urlog;~~~~o accomplished, for both the individual and common good. permeable paving 3 popcorn paving Permeable paving should be considered on sites where sandy, absorptive soils exist, since they allow infiltration of runoff into the soil and slow down the rapid flow of water to 3 swales and ditches from hard surfaces. Water moves /k. GAS through permeable paving into a layer of gravel and then /,:7-51 a> r 9 O1,L filters naturally into the underlying soil. The Waccamaw | Regional Plann;ng and Development Council can provide -..:..:~~-:- ; ' .Z -'~'::-.".:-.~','-'-~',; : ::r. N:~ : M advice on local sources, costs of permeable paving, and C9 b>>e; Y tOp <pt<-_ 4' 6JgH4 -i E conditions of use. 3 ' Porous asphalt paving, commonly known as pop- -,-~e=71L. corn paving, should be used on driveways, parking areas, and road surfaces where highly porous soils | exist. Where less permeable soils exist, borrowed aggregate paving surface proous fill from on- or off-site can be graded into areas that are to be paved. Clogging of the paving 3 pores by silt and sand may occur over time, but hosing or regular vacuuming and sweeping can pre- vent this from happening. Its strength and stability make it acceptable for a great range of access and parking conditions. 31 � Aggregate paving, such as gravel and crushed : stone, can also be used in areas of pedestrian and ... low-speed vehicular use. They provide better infiltra- n . . . . ..~ '~ tion than the popcorn paving and pavers set in sand, ' , J,./, although they do not possess their stability and re- < quire greater maintenance. They also require ade- ,_7/.xv.,'"-,...a,-r- '� ,- quate subgrade base depth where vehicular use is _- intended. I Precast interlocking and brick pavers, set on sand for increased absorption, can provide a hard support surface for pedestrian use on patios and sidewalks and for vehicular parking. Precast pavers are some- what more expensive than porous asphalt paving but are visually pleasing. E c. 0 Lattice block pavers contain hollow voids that can : be filled with sand, crushed stone, grass over porous - soil, or other porous material. Their use can be best applied to special parking areas where low speeds are suited to their masonry quality, improved quality Improved grading in residential, commercial, and other / large developments should direct runoff from parking lots, j, ...-., roadways, and grassed surfaces toward on-site areas that . can detain and either absorb or discharge rainwater slowly to other outlet points. uit-aer AT * ~~~~~~~~~~~~~~~~uni paers � The gradient of parking surfaces should not exceed 2% where feasible, to slow runoff and increase infiltra- tion through pavement pores. Where parking sur- r., faces are forced into steeper slopes, flatter bands or .1.. .,' landings should be graded at no more than 1 1/2-2%, ';/** . at suitable intervals, to intercept flow from the steeper areas and increase infiltration through the porous paving or other permeable material used. I Runoff should be shed toward swales, perimeter 6 ' ditches, medians, and other detention areas by proper grading design. improved grading for vehicular parking __.- TO____X infiltration structures Infiltration structures should be used to receive runoff from /'J / EP -'E driveways, parking surfaces, and lawn areas and to allow ,u /the runoff to be absorbed directly into the lower layers of t' ,, ~,, it rmtl>- "'~" A~ soil. Since soil will accept less infiltration with continuing a- t<, ~~~~_< _ - fI~rainfall, pits, dry wells, and other stone-filled drains are r~ _,---1 - - most effective at the beginning of storms. * Infiltration pits can be dug directly into the ground and filled with gravel, shell hulls, or porous rubble that typical infiltration pit is separated from the soil by a filter mat, and used to intercept and absorb runoff. The filter mat will prevent roof drain- tl /--l-porous paving soil from clogging the porous gravel and decreasing infiltration. * Dutch drains are linear infiltration pits or trenches I river stone splash layer______ filled with gravel or other coarse material. Dry wells, pits filled with gravel or stone rubble and ~gravel filled dry well .......r!_!._,,surrounded by a mesh soil separator or by a vertically set perforated fiberglass, concrete, or metal cylinder, overflow drain In can be used to collect stormwater from roof gutter roof downspout drainage infiltration trenchda downspouts. The water will be absorbed into the ground provided the soil is sufficiently permeable and unsaturated. * French drains, perforated pipes surrounded by _ P~osYue ?^~Sawye E E baitctSgravel, can be used to collect excess stormwater Ao__Olar 9 M from the base of dry wells in areas where less perme- able soils exist and lead it into areas of greater soil permeability or to drainage outlets. median strips Median strips can be designed without curbing to accept safe amounts of runoff from adjacent roadways and park- ing lots. Depending on their size, they can incorporate plantings of species tolerant of temporary wet conditions and urban stormwater runoff, along with linear infiltration pits. Not only can median strips absorb stormwater runoff 3 - passing excessive amounts on to other on-site outlet points - but they may also filter out pollutant collected by 33 runoff. * The size of median strips should vary depending on planning requirements and the overall dimensions e , e and requirements of each site. * Dutch drains may be used along the perimeter of medians to help intercept runoff, store it, and allow it to percolate into subsurface soils. Filter fabric should ,) . M be used to separate gravel from the bordering soil to prevent clogging. * Perforated wheel stops should be used to allow .t runoff to flow through their base and into medians. They are typically precast in concrete and have horizontal voids in their base.J -O . * French drains should be used to carry excessive A,, stormwater from Dutch drains to permeable soils or outlet points.r ,u1, * Sweeping and vacuuming on roadways and parking lots should be performed on a regular basis ?glec'u1, to reduce clogging of pores caused by fine particles A1 46 of soil and other debris. roadside drainageways Roadside drainageways should be designed to ensure ef- median strips intercept and absorb runoff ficient roadside flow by properly locating ditches, culverts, and pipe inverts. Elevations should be specified by a quali- fied professional to avoid local blockages and overflow. * The design of street storm drains and catch basins in built-up areas of Myrtle Beach should be designed to ./ ?- ~-- t accept that runoff which cannot be accommodated ' Ale by roadside absorption. t - * Low, dense grosses should be planted on swale r - t <t bottoms, slopes, and adjacent areas to stabilize soil .- a s ' and restrict weed growth in low density areas of the city. precast concrete wheel stops with runoff cuts * Side slopes of sandy, unstable soil should be cut at 45%. In areas where clayey soil exists, 60% is acceptable. * t perimeter ditches Perimter ditches, or a principal drainage channel, should be located around shopping centers and other large de - velopments to accept a portion of parking lot and road- __ , ~way runoff while providing an opportunity for natural ab- sorption and evaporation, and to carry runoff into an on- site detention pond where feasible. . Construction principles for perimeter ditches should follow those for roadside drainageways. detention ponds Detention ponds should be designed to store on-stie runoff -~ '-~- 's.- ~ collected from storm drains, Dutch drains, French drains, swales, perimeter ditches, and paved and unpaved sur- faces. During periods of moderate and high rainfall, de- onsite stormwater detention design tention ponds release excess amounts of stormwater into natural water courses or mand-made systems. At other periods in time, they allow for vegetative absorption, eva- poration, and natural infiltration of detained water. * The size of detention ponds should not be determined by their function of controlling stormwater alone, but with consideration given to their potential as recrea- tion areas, groundwater resuppliers, aesthetic re - sources, or other uses. A larger than mimally sized pond can yield various benefits to the owner. a Weirs provides outlet of excess stormwater at pond edges and should be designed and set at a proper elevation by an engineer or other professional, Weirs may also be arranged to hold back a higher head of water during storms than during fair weather and thus . ~:--~ aid in flood control. landscaping The use of native or exotic (imported) trees, shrubs, and ground cover should be incorporated into residential homesites, shopping centers, and other large developments. 35 * Existing vegetation should be protected from con- struction practices and retained as extensively as � Low, dense grasses, such as tight-growing Bahia, Ber- muda, or Common Lespedeza, should be planted on swale and drainageway bottoms, sloping sides, crests and perimeters, and on other unvegetated bare soil surfaces. Grassing will soften initial rain im- pact on soil, slow runoff, and help moderate fluctua- / tions in ditch flow. - o I Dense vegetative ground covers and heavy mulches, such as gravel, rocks, and shell hulls, may be used in plant beds, median strips, and areas where the soil is void of cover to prevent erosion and landscaping controls stormwater and improves aesthetic appearance retain moisture necessary for plant establishment and survival. � Root zones of plantings should be slightly elevated by berming where standing water is likely to occur, espe- cially in median strips. � Invasive vegetation, including types with intrusive root systems, should not be used in areas where they may cut down absorptive capabilities of French drains, infiltration pits, and other runoff conduits. 0 A local landscape architect can best provide infor- mation on plant types, their availability, design, and other pertinent landscape information. locating pools, patios, and parking at a safe setback Swimming pools and impervious patios, along with parking facilities, should be moved from within the proposed swale absorption zone (Zone 2) to the positive drainage and ab- sorption zone (Zone 3) wherever feasible. This would allow "' "-!i for the redevelopment of a protective dune ridge and an absorptive swale. additional parking relocated pool * The location of relocated pools should be designed to take advantage of southern exposures where possible. * Large swimming pools could be designed for joint X3_ i;I ; use by neighboring motels rather than relocating small, separate versions, where owners can agree. parkingC hi A; [� _ E � * Porous pavings should be used on all proposed and remaining pool perimeter surfaces, on all parking sur- faces, and on all public and private pathways. .4 f-fi Aid<><2aeq,' � Landscaping should be incorporated within parking o-f ~ u- Ad medians on path borders, and around pool patios. f ..... '".-.-:_~' ~ .,. � - jVegetation, mounding, and swales will assist in storm- water runoff control. eoreddune's " � Public and private infiltration structures should be restored dunes used, where necessary, to further facilitate runoff control. concept for pool, patio, and parking setback mounding Mounding can be accomplished on individual house lots POOF . I-r' q,2ID d-Ly. and on large parcels of developed land by grading exist- t1A'TFew' rr1 t�-4wTH ing on-site soils and borrowed fill. The benefits of mounding / L~4'EP e F2~4S oI~j Polk~ Grare the improvement of protection of houses, motels, and i eMJ1OV5ip ae-rH rJCuzD other valuable structures from stormwater flooding, the shaping of the remainder of the site for better infiltration, and achievement of a more attractive landscape. py!'-__J4. -PH* � Slopes should permit runoff to flow at an even, non- erosive rate into adjacent swales. * Landscaped mounds may increase the rate of runoff --.-liii ~ ~away from the valuable structures, but the adjacent ,,- C-rO rIc :-. , swales will tend to slow down and absorb the runoff IIt I - flow. fr llJ-~ H IIE * "i'.-'-,j-�On-site sewage disposal units within mounded k-t1 -rE D -1 homesites should be placed in porous soil away from less permeable soil and away from shallow water both flood protection and groundwater protection are improved tables. 37 4 3 [ 4 2 4 2 3 4 5 2 ___aBB 9-~7 _ I M , - - Myrtle Gateway Chapin Gateway Pavilion Gateway 30th N 29th N 26th N 27th N 26th Nth N 24h N 24rdN 22nd N 215t N 20th N 19th N 18thN 17th N 16th N 15th N 14th N th tth* N LEGEND 1 ---l ~sMean High Water (City base, 1977) Beach gateway (access of special 1 2 Dune/Swale Reconstruction Potential ill aesthetic importance) Mean High Water (RPI, 1981) aesthetic importance) Dune/Swale Reconstruction Typical Parks and streets of special public Potential (1) Measures (2) (1) Source: Research Planning Institute, Ihc. November 1981 Backlands and beach with high public access importance 1 Excellent D/SA (2) Typical Measures: open space enhancement potential 1 i 1 1111111111 iii I Xa XAreas in which consolidation of public walks 2 Good, some problems D/B/S/A D Dune reconstruction (zone 1) FE:?' Backlands with Umited enhancement potential would be beneficial 3 Fair, numerous problebms D/B/S/A B Berm construction (zone 1) Ocean Boulevard frontage: improvements of 4 Poor feasibility without B/D/A S Swale development (zone 2) (1) parking capacity, (2) pools and patios some renurishment A Absorptive repaving (zone 3) (3) streetscape image 5 Infeasible without major B/A renourishment *3/4 Reconstruction Potential 3 where no parking lot exists 4 where parking lot exists l swales } Swales should be graded in conjunction with mounds to slow the rate and amount of runoff entering roadside and , l other drainageways. * The location of swales should be along natural drain- , , l age paths in the lower and border areas of the site. * The grading of swales should be designed to assure ". i- the flow of runoff into roadside drainageways so that standing water does not occur. * Side slopes should be designed to allow for a slow, c even flow of runoff, enabling the swales to absorb water and reduce downstream flooding. j * Grasses, such as tight-growing Bahia and Common Lespedeza, should be planted in swales to help slow runoff, stabilize soil, and restrict weed growth. swales slow runoff entering roadside drainageways and natural watersheds controlled roof drainage Controlled roof drainage should be achieved by using infiltration structures in residential and commercial developments. * Rooftop drains that utilize a strainer and detention __ ring to ensure a safe, moderated release of water into a drain pipe should be used on large, flat roofs in shopping centers and other commercial '"~,r',, " : +, .P4,. .SJ developments. dune and swale reconstruction and maintenance Dune and swale reconstruction and maintenance on resi- dential, commercial, and other properties bordering the rooftop drain beach should follow the techniques proposed within the "What the Public Can Do" section of this report. 38 : : . 0 0 -0: Ad :"': -.dune walkover structures I Beach access and dune walkover structures should be used by all private and public property owners to provide :: :: beach access. The proposed structures and techniques for construction can be found within the "What the Public Can Do" section of this report. revetments, seawalls, bulkheads, and acceptable alternatives Wherever possible sand dunes backed by a swale should be used instead of revetments, seawalls, or bulkheads. Where structural erosion controls are decided on, a sloped revetment that utilizes adequately-sized stone layed on a sloped bank of crushed stone and that is backed by a filter mat should be used instead of a seawall or bulkhead. t.h ",,000000 vIK i:: 0 if 00 Wherever possible, sloped revetments should be sited in accordance with an adequate setback from the beach. Seawalls and bulkheads are undesirable because prob- lems of wave reflection and beach scouring and beach .. .. erosion that occur with their use intensify beach erosion. | I The fold-out map opening on the right summarizes recommendations for a four-zone stormwater runoff management approach, unified with improved public street ends, public parks, and other beach landscape features. Together, these can potentially enhance the water quality, beach quality, and landscape quality of Myrtle Beach's ocean frontage. The proposed plan is based on recommendations, ideas, and commentary developed at a series of public meetings held in Myrtle Beach in 1980 and 1981, sponsored by the City of Myrtle Beach and the Waccamaw Regional Planning and Development Council, at which Roy Mann Associates, Inc., and Moore, Gardner & Associates, Inc., provided technical support. 39 * ~~~m (21Th1~~~~~~~~dnfe~ beach . hn ec ~~~~~~~~~~~~~~~~~~~~~~~~~~rehblocated dnswiiigpo rellocated swhvnft pod ~~~~~~~~~~~~~~path rises to h~ih point to aim in -etadrig nm-off from reac~ing &Me zone pubic walk narrowed to 10 ft. public waik widened to 30 ft. poro u ~ ~ ''s a~ c mateial street end redesign concept for increased runoff control 4 ~~~~~~~~~~~~~~~~~~~40 4 3 5 2 I15th Street Gateway ~~~~~~~~~~Hurl Rocks '?~,. I II i~t~~Z --h- - -----h SEW 10th~ ~~~~~~~~~~~~~-~ S3 liths lthS ips l~thS 1t 20th a 9th lth lth 12h 13hS 149 Iit SUNIFIED CONCEP PLAN Sermion 5/Stormwater Runoff Contral Study Area Myte Beach, South Carolina Wyaccarnaw Regional Planning and Development Council Roy Mann Associates, Inc., consultant ( Museum Wharf, Boston. Massachusetts ( a s 0 100 200 coo 1 *~~~~~~~3/4 4 5 I Water. 1977 ~~~~~~~ ~~~~~~~~Withers Swash 13Wtr197-- Gatleway Mean High Water 1981 -- *--~~~~~~-r _ - n N-d rdS4 __~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ft t t Styh conclusions Through use of the techniques and action steps outlined in this handbook, improvements in stormwater runoff man- agement, public access, and the beach and dune land- scape of Myrtle Beach can be achieved.3 With progress in these areas, less beach erosion and water quality impairment will be caused by stormwater runoff. The beach will offer a better and safer recreational experi- U ence, Many properties will enjoy better protection from ocean storms, through improved setback of pools and other built elements from the dune zone. The landscape of 3 the ocean frontage of the hotels and motels of the city - so vital to Myrtle Beach's tourism and vacation economy - will be enhanced. Public access from Ocean Boulevard will be improved and made more enjoyable, And im- proved parking capacities along Ocean Boulevard will provide better parking than can be found in parking en- croachments upon the dune zone, where parking surfaces I are vulnerable in any event to storm damage. Benefits to the owners of private sites away from the beach can include improved protection from on-site flooding and the added landscape quality that properties will enjoy where sites are designed, graded, and planted to en- courage infiltration of rainfall into soil and porous surfaces and the location of buildings on higher, contoured ground.3 In summary, the public of Myrtle Beach has at its disposal effective tools for stormwater control and environmental quality improvement. Both the public at large and indi -3 vidual owners of property have a golden opportunity to take advantage of these tools - now - before beach ero- sion, water quality impairment, and other storm-related problems grow to levels of higher and higher economic, health, safety, and environmental costs. 413 for further assistance suggested reading For further information on ways in which y~u can help minimize drain- Dames and Moore, Design and Construction Manual for Residential age problems, please contact: Buildings in Coastal High Hazard Areas. U.S. Department of Housing c Waccamaw Regional Planning and Development Council and Urban Development,1981. 1001 Front Street E.M. Seabrook, Jr., Inc.., and Cubit Engineering Ltd., Myrtle Beach Georgetown, South Carolina 29440 Dune Restoration Study. South Carolina Coastal Council, 1981. (803) 546-8502 Georgia Department of Natural Resources, Handbook: Building in the * The City of Myrtle Beach Coastal Environment. 1975. Post Office Drawer 2468 PoTenth AvenueNorth 2468 Hayes, Miles O., Thomas F. Moslow, and Dennis K. Hubbard, Beach Myrtle Beach, South Carolina 29577 City Manager (803) 448-2430 Moore, Gardner & Associates, with Roy Mann Associates, consultants on non-structural alternatives, Final Evaluation of Stormwater Control Landscape Architect (803) 448-2347 Landscape Architect (803) 448-2347 Alternatives. Waccamaw Regional Planning and Development Public Works Department ounci, * Myrtle Beach Hotel and Motel Association Planning Department of the City of Myrtle Beach, The Myrtle Beach Post Office Box 1303 Plan. Myrtle Beach, South Carolina 29577 Research Planning Institute, Inc., Beach Scraping and Back-Beach Fill (803) 626-9668 Plan. City of Myrtle Beach, 1981. Roy Mann Associates, Inc., Managing Storm Drainage Through Im- proved Land Design. Waccamaw Regional Planning and Develop- ment Council, 1982. Roy Mann Associates, Inc., Managing Storm Drainage Through Improved Land Design (slide-tape). Waccamaw Regional Planning and Development Council, 1981. Untermann, Richard K., Grade Easy. American Society of Landscape Architects Foundation, 1717 N Street, NW, Washington, DC. Waccamaw Regional 208 Areawide Water Quality Management Plan. Waccamaw Regional Planning and Development Council, 1978. I A'A acknowledgements credits Waccamaw Regional Planning and Development Council Roy Mann Associates, Inc. Leslie Mclver, Chairman .Roy Mann, Project Manager Kenneth C. "Ken" Thompson, Executive Director Michael Smiley, Beachfront Analysis/Public Meetings William J. "Bill" Schwartzkopf, Director of Planning Perry Howard, Street End Design Larry Schwartz, Project Director Mark Sorensen, Plan Graphics Jimmy A. Williams, Environmental Planner Peter Jackson, Analysis Arthur J. Neumann, Text City of Myrtle Beach Sam Coplon, Text Erick B. Ficken, Mayor Robert Hanss, Drawings Carey F. Smith, City Manager Jeffrey W. Piro, Technical Drawings James E. "Jim" Tolbert, City Planner Jeffrey Brandenburg, Report Production M. Leland Smith, Landscape Architect . Ronaleland Andrewsmith, Public Works Director Moore, Gardner & Associates, Inc. (provided input and review) E. Ronald Andrews, Public Works Director David Stradinger, City Manager (retired) Dr. Newton V. "Newt" Colston, Civil Engineer and Vice President Samuel "Sam" Burns, City Planner (retired) of Moore, Gardner & Associates William Howland, City Engineer (retired) Owen W. Bludau, Civil Engineer Michael F. Redmond, Civil Engineer Myrtle Beach Hotel and Motel Association Anthony V. "Val" Nicholson, President Carl Coward, Vice President Research Planning Institute, Inc. Timothy W. Kana 43