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HomeMy WebLinkAboutCT 83-06; RANCHO CARLSBAD COUNTRY CLUB; FLOODINGS; 1983-04-06s CT'1-3 PLAIN Reference is made to sections of Conditional Use Permit from City Engineer, City of Carlsbad, dated November 19, 1968. Subject: Pre annexation Conditional Use Permit Mobile Home Park, El Camino Real. ***************** This development is id the flood p1ainof A..za Hedionda Creek. A hydrological study is required to determine the possible extent of flooding. All areas subject to inundation shall be shown .on the final sub-division map. -, City requires that certain .storm' drains be Installed and that they be held harmless for any -flood damage regardless of their installation. • •• .• • - • • • •: • • •• The following report, and attachments thereto, emphasize the conditions and dangers, that exist within the confines of...-. Rancho Carlsbad. Such conditions and dangers have repeatedly been reported to the management of Rancho Carlsbad and to the responsible officials of the City of Carlsbad. S. HORACE K. CHURCH, C. E. EARTHMOvING CONSULTANT ( - 3434 DON PORN RIO DRIVE RANCHO CARLSBAD CARLSBAD, CALIFORNIA 92008 Office-Home-7141438-9165 0 . TI.e8_0(p April 6, 1983 I SUBJECT; Floodings in Rancho Carlsbad Mobile Home Park. Causes and Stop-Gap Remedies. Gentlemen: I have been asked to, discuss the subject. I have lived in the Park for 10 years; thusly 'I am able to discuss the floodings, causes, and remedies from the subjective viewpoint of a resident, and the objective standpoint of an engineer. The floodings are of two kinds: first, the dangerous and destructive one of January, 1978; and second, the yearly aggravating floodings during the Fall-Winter-Spring heavy storms of the past ten years. ' HISTORY . The Park is located atop an old flood-plain similar to many lowlands of coastal San Diego County. Into this flood-plain debouch southwesterly flowing Calavera Creek and northwesterly flowing Hedionda Creek. These streams, with their burdens of clays, silts and sands, built the flood-plain which extends south-easterly beyond the Park. The streams had no fixed channels, as they simply meandered over the flood-plain in a braided pattern. During historical times they must-have covered the flood-plain many times with shallow and deep lagoons. The watershed of Calavera Creek is large, and it included the vast Calavera Reservoir with its huge volume of impounded water. The watershed of Hedionda Creek is greater. Both Streams are raging torrents during floodings. In addition to water from its natural watershed,' Calavera Creek receives overflow from the reservoir. The drawing on the next page shows the size of. the Park. Both creeks were channelized as part of .the grading plans. Note that there is outlined the flooding "--------•----" - -. :. -. area for for a 100-year storm. It shows that Hedionda Creek would overflow its banks and would flood some adjoining streets. 0 What it does not show is that the January, 1978, flood inundated the northeastern part of the Park even though this storm was of far less intensity than that of a 100-year storm. In the 1978 flood, the Arizona-type bridge at Rancho Carlsbad Drive was inadequate. Hedionda Creek backed up through the upstream golf course, over-flowed its banks in the flood-plain, and spread its waters to the northward and to the north westward. The northeastern part of the Park was flooded to a depth of.ZM feet. Pictures of the appended Rancho Carlsbad Flood" illustrate this debacle. The minor floodings of the past ten years have been mostly in street inter- sections, notably at the joinings of Don Juan Drive with Don Porfirio, Don Jose, and Don Alvarez Drives. At these locations, waters frequently spread above tops of curbs and from curb to curb. These floodings of a continuous nature jeopardize Cl pedestrians and automobiles, and threaten landscaping, storage rooms, workshops, and storage sheds of home owners. CAUSES • ' , There are two causes for floodings. The chief cause is that the filling, which forms most of the Park, is not high enough above the surface of the existing flood-plain southeasterly of the Park. When Hedionda Creek in the area of 'the golf course its banks due to inability to carry the great, volume of water the 'flooding 'of the Park is a natural. result. If' the original design of earth work had provided from 0 to L. feet increase in elevation of filling, the problem-of flooding would not exist. ' The second cause Is lack of an adequate surface water drainage system. There .is-no sub-surface system below the streets, which would consist of essen-' tially main pipes, lateral pipes, and catch basins. The streets act as drainage channels to transport rain, mud and debris from the Park to the two creeks. Be.- cause the-flow lines-of some streets and gutters are not suitable, water and materials collect in 10w undrained areas. ' So -3- •s There are no practicable remedies for the two causes of floodings. The Park cannot be rebuilt even though half of the park: has been vacated and moved away. The raising of the land would be almost equivalent to building an entirely new Park. When and if this necessary change is made, it should be accompanied by equally necessary upgrading of streets, curbs and gutters, street lighting, sewers and utilities.- STOP-GAP RENEDIES Several changes and additions can be made to alleviate flooding conditions: The breached levee from the golf course to and beyond the tennis courts should be repaired, its height should be increased, and it should be provided with a spillway, An intercepting channel or ditch should be built along the street from the tennis courts to calavera Creek. Alluvia, deposited in Calavera Creek, can be removed to.provide 0 ( more water-carrying capacity in order to take care of the emergency 0 of un-watering Calavera peservoir. 0 CONCLUSIONS It is, unfortunate that specifications for building Mobile some parks are not as protective to people and property as are those for tracts for other homes.. •' Otherwise, it is unlikely that the park would be beset by these flooding con- ditions. In a sénse,..:if one may judge by the flood of january, 1978, the park in its configuration is a man-made elevated flood-plain adjoining the natural flood-plain to the south eastward. The unfortunate situation can be. corrected . 0 only by re-building the park, Very truly yours, jC ffKC:em 0 • Horace K. Church • C -- •••\••_•0 • 0 0 0• ......---------