Topanga Canyon Floodplain Management Citizensí Advisory Committee
TABLE OF CONTENTS
Section page
List of illustrations vi
List of tables viii
Foreword ix
Acknowledgment x
History of flood hazard and flood hazard management in Topanga Canyon 1
Executive summary 2
Recommendations 5
References 13
TABLE OF CONTENTS
PLAN APPENDICES
Section page
Topanga Creek Watershed Management Study: Findings Appendix A
1.0 Quantifying the flood hazard risk A-2
1.1 Floodplain Management A-2
1.1.1 Comparison of approaches A-2
1.1.2 County designated floodways A-3
1.1.3 Other approaches to floodplain management A-3
1.2 Whatís at risk A-4
1.3 Quantifying the risk A-6
2.0 Present practices exacerbating the flood hazard A-6
2.1 Runoff from new developments A-6
2.2 Infrastructure maintenance/improvement practices A-8
2.2.1 Shoulder fill and dumping A-9
2.2.2 Trees A-9
2.3 Grading and brushing A-13
2.4 Alteration of stream flow characteristics A-16
2.5 Debris hazard A-16
2.6 Emergency road maintenance practices A-19
3.0 Review of present flood hazard policy and regulations in Topanga Canyon A-21
3.1 Federal programs: FEMA/NFIP/CRS A-21
3.1.1 NFIP regulations A-21
3.1.2 CRS program A-21
3.1.3 Mitigation of unsafe conditions A-22
3.2 State A-23
3.3 Los Angeles County A-24
3.4 County designated floodway A-25
3.4.1 Floodway and flood fringe A-26
3.4.2 Historical rationale for the floodway ordinance and maps A-26
3.4.3 Floodway mapping A-26
3.4.4 Impacts of a County designated floodway A-27
3.5 Policy Consistency A-32
3.5.1 Stream management A-32
3.5.2 Public health and safety A-33
3.5.3 Drainage Policy A-36
3.5.4 Vegetation removal for fire safety A-37
3.5.5 Policy summary A-38
TABLE OF CONTENTS
Section page
Topanga Creek Watershed Management Plan:
Statement of Goals and Policies Appendix B
1.0 Goals B-1
2.0 Policies B-2
Topanga Creek Watershed Management Plan: Plan Elements Appendix C
1.0 Watershed master planning C-1
1.1 Hydrology C-1
1.1.1 Validation of the hydrologic and hydraulic models C-2
1.1.2 Reduction of peak flow runoff C-3
1.1.3 Runoff suppression C-12
1.1.4 Need for additional data for hydrologic models C-17
1.2 Land use C-17
1.3 Channel management C-18
1.3.1 Stabilization of creek banks C-19
1.3.2 Channeling of main watercourses C-19
1.3.3 Filling of low points C-19
1.3.4 Hydraulic structures C-19
1.4 Coordination with other programs C-21
2.0 Development Standards C-24
2.1 Implementation C-24
2.2 Hazard mitigation C-24
3.0 Environmental site planning techniques C-26
4.0 NPDES stormwater runoff best management practices C-27
5.0 Maintenance and education program C-28
5.1 Communication and community awareness C-29
5.2 Environmental review process C-30
5.3 Road shoulders (DPW and Caltrans) C-30
5.4 Streambank stabilization C-30
5.5 Stream channel maintenance C-31
5.6 Line clearance/utility maintenance C-31
5.7 Repairs of bridges and stream crossings C-32
5.8 Riparian vegetation protection C-32
5.9 Exotic flora eradication C-32
5.10 Illegal dumping C-32
5.11 Prescribed burns C-32
TABLE OF CONTENTS
Section page
6.0 Watershed research and restoration programs C-32
6.1 Water quality analysis C-33
6.2 Sediment and erosion control analysis C-33
6.3 Creek bank stabilization study C-33
6.4 Tree inventory C-33
6.5 Biological inventory C-33
6.6 Exotic flora and fauna eradication C-34
6.7 Restoration of the Topanga Creek estuary C-34
7.0 Early warning systems and emergency response C-34
8.0 Economic feasibility and considerations C-36
8.1 Grants C-36
8.2 County support C-37
8.3 Fees C-37
TABLE OF CONTENTS
TECHNICAL APPENDICES
Section page
FEMA/NFIP regulations Appendix D
Value of trees and riparian vegetation in streambank stability Appendix E
Grant sources Appendix F
Complete list of recommendations made in this report Appendix G
Actions needed to develop required water quality data Appendix I
Topanga Creek Watershed Management Plan land use recommendations:
consistency with adopted local area plans Appendix J
Documents related to Los Angeles County floodplain management Appendix K
Letters of consultants Appendix L
Description of hydrologic models Appendix M
list of illustrations
Figure Page
A-1 Summit Pointe development. A-10
A-2 Grading practices to increase sedimentation and peak flow runoff. A-11
A-3 Potential locations for detention basins, existing sites. A-12
A-4 Erosion of road shoulder fill. A-14
A-5 Soil dumping along road embankments A-14
A-6 Tree impacts from road maintenance practices. A-15
A-7 Results from clear cutting and disking for fire protection
and lot development. A-17
A-8 Examples of grading and infill practices which generate
increased peak flow runoff. A-17
A-9 Example of an alteration of the stream flow characteristics. A-18
A-10 Large pieces of debris that should be removed from
the major watercourses. A-18
A-11 Results of emergency repairs at various locations along
Topanga Boulevard and Old Topanga Canyon Road. A-20
A-12 Schematic representation of a natural floodplain. A-28
C-1 Detention basin at Corona del Mar. C-4
C-2 Topographic map of portion of upper watershed in Topanga
(near Old Topanga Canyon Road). C-6
C-3 Potential location for detention basin, site 1. C-7
C-4 Potential location for detention basin, site 2. C-7
list of illustrations
Figure Page
C-5 Detailed topography for the potential detention basin sites C-8
C-6 Other potential sites for detention basins (serendipitous sites). C-9
C-7 Depicts increased erosion where drain pipe installed below pad level;
if installed differently, decrease of peak flow runoff could result. C-11
C-8 Generic design for pervious pavement. C-16
C-9 Newly installed culvert in Red Rock Canyon. C-23
C-10 County highway bridge at risk of washing out in the 50 year storm. C-23
M-1 Rainfall intensity curve for Topanga (Zone M). M-3
M-2 Portion of DPW hydrologic model for Topanga: the upper watershed,
mostly to the west of Old Topanga Canyon Road. M-5
M-3 Variation of runoff coefficient with rainfall intensity. M-10
list of tables
Table Page
A-1 Flood hazard mitigation activities suggested by FEMA A-35
C-1 Estimate of detention basin capacity needed to reduce the
peak flows from a 50-year storm to those of a 10 or 25-year storm C-10
C-2 Estimate of detention basin depth needed to reduce a 50-year storm
to a 10 or 25-year storm C-10
C-3 Criteria which trigger runoff mitigation measures C-15
C-4 Protocol for determining potential increases in peak flow runoff due to development C-16
M-1 Peak intensity-duration data, M zone M-4
M-2 Calculated flow Q for various sub-regions in upper Old Topanga,
for the 50-year design storm M-6
FOREWORD
In 1990 the Los Angeles County Department of Public Works proposed to adopt a Floodway Ordinance for the upper portion of Topanga Creek adjoining Topanga Canyon Boulevard. The Floodway Ordinance was intended as a regulatory tool to mitigate potential flood hazards associated with development in, or adjacent to, the Topanga Creek floodplain. Topanga residents reviewed the proposed ordinance and identified a number of significant concerns including the efficacy of the ordinance to protect residents from flood hazard, and the long term environmental and social impacts that would result from adoption of the ordinance.
In response to their concerns, Los Angeles County Supervisor Ed Edelman asked Topanga residents to prepare an alternative plan to the Floodway Ordinance. In September, 1992, the Topanga Canyon Floodplain Management Citizensí Advisory Committee (TAC) presented their report "An Alternative Plan to the Proposed Topanga Canyon Floodway Ordinance" to the Board of Supervisors. The Board accepted the report and in March, 1993 TAC was directed by the Board of Supervisors to prepare a watershed management study to address flood concerns including means to reduce storm water runoff, control soil erosion, and improve water quality.
With the continued support of Supervisor Zev Yaroslavsky, the Topanga Canyon Floodplain Management Citizensí Advisory Committee has completed its study for the Board of Supervisors. The Topanga Creek Watershed Management Study incorporates the following elements:
An analysis of the existing hydrologic methodology used by DPW to determine the flood hazard in Topanga Canyon
Analysis of the environmental effects of the existing and proposed methods of integrated flood hazard management
Analysis of the economic and social factors associated with floodplain management
Alternative means to manage the flood hazard in Topanga
The recommendations of the Watershed Management Study are presented to the Board of Supervisors as a set of actionable items that will allow integrated management of the flood hazards in Topanga Canyon. The study recognizes the need for fiscal austerity at all levels of government and the recommendations are intended as cost effective strategies which will be of benefit to all of Los Angeles County.
ACKNOWLEDGMENT
The members of the Topanga Canyon Floodplain Management Citizensí Advisory Committee represent several groups.
Topanga Association for a Scenic Community (TASC),
Topanga Canyon Town Council (TCTC),
Topanga Canyon Creekside Homeowners Association (TCCHA),
Resource Conservation District (RCDSMM),
and advisory members representing the County of Los Angeles (LACO).
Joan Andersson, J.D., TCCHA
Rabyn Blake, M.F.A., TCCHA
John Crawford, P.E., TASC
Phil Chandler, C.E.G., TASC
Rosi Dagit, Conservation biologist, RCDSMM
Dick Olsen, TCTC
David Phillips, Ph.D., TCCHA
Carl R. Nelson, P.E., LACO
Irving Sherman, P.E., LACO
Martha Witter, Ph. D.,TASC
HISTORY OF FLOOD HAZARD AND FLOOD HAZARD MANAGEMENT IN TOPANGA CANYON
Throughout this century, heavy rains have come once or twice a decade to Topanga Canyon, with major floods recorded in 1938, 1969 and 1980. Heavy downpours on the heels of prolonged periods of wet weather have done damage to the entire watershed, causing inundation and slides in the uplands with destructive erosive flooding of the creek areas. Accounts in The Topanga Story [24] relate the elemental struggles that occurred during the floods with evacuation, procuring food, attempts to reunite families, and tragically, the death of five people in 1969. The experiences of the residents during these emergencies have prompted concerns for a proactive approach to flood hazard reduction.
During major floods, low-lying areas, including Topanga Center and some houses, have experienced minor inundation flooding. The main damage however, has been to roads, primarily Topanga Canyon Boulevard [State Route 27], an important commuter thoroughfare to the Westside. In 1978 the road was closed for two months for flood repairs. In the "worst flood of the century", February 16, 1980, Topanga Canyon Boulevard was altogether gone in two long stretches of up to 200 yards, and it collapsed in half a dozen other locations, requiring a massive engineering repair job. In 1969, the road repairs lasted from February through the following June. The miracle repair of the boulevard in January 1995, when another section of the Boulevard collapsed, took less than a month thanks to the intervention of our new Supervisor Zev Yaroslavsky and the round the clock performance of CalTrans. The Department of Public Works (DPW) clears and repairs County roads with equal dispatch, and the DPW and the Fire Department have always come to the rescue in times of disaster with sandbags and advice to homeowners
Following the 1980 flood, DPW, under contract to FEMA, mapped the Topanga floodplain to comply with requirements of the National Flood Insurance Program (NFIP) using a 100-year storm. The resulting maps, known as the FIRM maps, are used by the Building Department, insurers, and property owners to identify flood hazard locations. DPW has proposed to change from a flood hazard mitigation system based on the FIRM maps, to one based on its own estimate of the extent of the flood hazard. The new maps, based on DPW calculations, portray a much larger zone of flood hazard than was designated on the FIRM map.
It is clear that the old ways of waiting for disaster to happen and then responding with emergency repair funds cannot continue to serve the community's and the County's needs. In this report, we propose that in the 21st century a new concept, that of watershed management, be employed. It is our intent to not only identify the flood hazard, but to develop measures to reduce it, as well as to maintain the natural resources of the stream channels.
EXECUTIVE SUMMARY
Topanga Canyon experiences periodic flooding along its creek channels that has the potential to threaten life, property and infrastructure. The Topanga Creek Watershed Management Study addresses the regulatory and policy framework whereby Los Angeles County can mitigate the Canyon's flood hazards. Implementation of the recommendations presented in the study will mitigate the impacts from flooding and reduce the costs associated with recurring disaster recovery efforts.
The Watershed Study is made up of three parts: Recommendations; Analysis of existing practices; and the proposed Topanga Creek Watershed Management Plan [TCWMP].
Recommendations. The recommendations of this report are based on the specific findings presented in Appendix A and C and on the Goals and Policies of the Topanga Creek Watershed Management Plan described in Appendix B.
Appendix A. This appendix analyzes existing practices including hydrologic modeling to determine the magnitude of the flood hazard, practices which exacerbate the flood hazard, and regulations that govern flood hazard protection in Topanga Canyon including FEMA, State, and County regulations.
Appendix B. This appendix describes the broad goals and policies of the Topanga Creek Watershed Management Plan that guide the specific implementation measures proposed to provide flood hazard protection and preservation of community and natural resource values.
Appendix C. This appendix describes the specific elements of the proposed Topanga Creek Watershed Management Plan including master planning, development standards, site planning, NPDES best management practices, maintenance and education programs, research and restoration programs, early warning systems and emergency response, and economic feasibility.
Technical Appendices. Reference material and technical analyses are presented in a series of Appendices D-M.
Based on four years of extensive review and analysis of floodplain management, we believe that the Topanga Creek Watershed Management Plan (TCWMP) offers significant benefits to the community compared to the Proposed Topanga Floodway Ordinance (PTFO).
Saving Lives and Property. The TCWMP provides for measures that include floodproofing, channel clearance, peak flow detention to reduce flood hazard, and community early warning systems. The TCWMP emphasizes preparation in advance of a disaster. The PTFO "no encroachment" requirement encourages temporary protection measures under emergency conditions, which place life and property at increased risk.
The TCWMP offers greater protection to infrastructure by reducing or preventing an increase in the amount of runoff throughout the watershed and by identifying priority sites for protection or upgrading. The PTFO regulates development only within the boundaries of the Floodway and allows increases in surface runoff. The volume of increased runoff allowed by DPW is equivalent to the amount of runoff generated under the most extreme disaster conditions following wildfires. The PTFO therefore encourages adverse amounts of surface runoff and extends the boundaries of the flood hazard area.
Saving Money. The TCWMP is more cost effective than PTFO by implementing preventive measures that will ensure survival of life, property and infrastructure. Prevention of damage to roads, culverts and bridges will save money in post disaster reconstruction. The local economy will also benefit when business operations and public access remain open. The proactive measures of the plan can reduce flood insurance rates, claims and federal losses. In comparison, the PTFO awaits disaster and then relies on emergency funding for repairs and upgrades of infrastructure. Emergency repairs are usually more expensive both in the scope of the projects and in the costs to have repairs finished rapidly using overtime and completion bonuses. Emergency repairs create additional, secondary economic losses due to lost work time, other social dislocations, and environmental degradation of the riparian zone.
The PTFO increases the cost of disasters by increasing the magnitude of the flood damage which results from the increased surface runoff allowed under the ìCapital stormî standard for new development. The federal and state governments have spent millions of dollars to prevent downstream property damage from runoff following wildfires. The same economic benefits should apply to the protection of downstream properties, when the level of runoff due to upstream development is increased by the same magnitude as that produced by a natural disaster.
Protecting the Environment. The TCWMP provides the added dividend of an improved watershed in which the riparian areas will prosper. The TCWMP fosters ecologically sound, comprehensive planning practices throughout the watershed, which will be reflected in a healthy creek habitat. The PTFO assumes, and allows as the typical condition, a volume of runoff that occurs only under the most extreme conditions where wildfire and heavy rainfall occur together. This runoff standard allows the creek environment and adjacent infrastructure to be destroyed by exceeding the natural capacity of the creek channel.
Conclusion. With the primary objective of reducing the flood hazard to existing life and property, the TCWMP is a better means to protect people, property, money, and the environment than the PTFO. The watershed plan proposes measures to reduce peak flow runoff, erosion, sedimentation and flood hazard while protecting the riparian habitat, infrastructure and existing development. This proactive approach benefits residents, property owners, and public agencies responsible for public safety and infrastructure. Prevention of flood hazard results in improved safety for all inhabitants and visitors to Topanga.
The PTFO does not reduce the flood hazard, nor does it protect existing life and property or natural resources. It is unnecessarily restrictive and would result in a disproportionate burden upon the existing creekside residents of Topanga. It does not mitigate the physical effects of flooding, siltation, and scour since creekside regulation is not complemented by watershed-wide measures. The PTFO addresses the end result of potential flood hazard without correcting the underlying causes.
The Topanga community has the commitment, and the social and political stability to sustain the TCWMP and to accomplish its goals of improved flood hazard safety and protection of our natural resources. The TCWMP brings together the expertise of many jurisdictional agencies within the County for the common good. It will not only fulfill the County's requirements for FEMA, but offer them a leading role in innovative floodplain management as we approach the twenty-first century.
RECOMMENDATIONS
The following recommended actions are based upon the Topanga Creek Watershed Management Study presented in this report. The report details the present flood hazards and regulations, and describes the Topanga Watershed Management Plan which has been designed to address these hazards.
overview of requested
Board of Supervisor Actions
ACTION I: Adopt a Topanga Creek
Watershed Management Plan
ACTION II: Establish the Topanga Creek
Watershed Management Committee
ACTION III: Implementation of the Topanga
Creek Watershed Management
Plan
ACTION I: Adopt a Topanga Creek Watershed Management Plan
Adopt the Topanga Creek Watershed Management Plan (TCWMP) Ordinance including:
The California DWR Model Floodplain Management Ordinance with FEMA minimum standards.
The regulations and best management practices listed in Appendix G.
A revised Channels Ordinance to allow removal of large debris and obstructions
A Santa Monica Mountains Community Standards District to implement land use policy.
Restrictions on certain paving, grading, and brush removal practices and on new developments to prevent additional peak flow runoff at a property boundary.
Allowance for reconstruction of damaged structures, where the damage is from non-flood related causes.
ACTION II: Establish the Topanga Creek Watershed Management Committee
Create the Topanga Creek Watershed Management Committee (TCWMC) to:
Oversee the coordination and implementation of the TCWMP.
Be composed of the public agencies with jurisdiction in the Topanga Creek Watershed and community representatives
Determine legitimate and reasonable policy measures to remedy the conflicts between public health and safety, drainage compliance, fire clearance, access, and project requirements.
Perform an oversight function to ensure that the provisions of the TCWMP are implemented.
ACTION III: Implementation of the Topanga Creek Watershed Management Plan
RELATION BETWEEN RECOMMENDED BOARD ACTIONS AND THE GOALS, POLICIES AND RECOMMENDATIONS OF THE TCWMP
Recommendations related to the implementation of the Topanga Watershed Management Plan (TCWMP) have been made throughout Appendices A, C and M. The relation between these recommendations and the goals and policies of the TCWMP is defined in the following tables. In addition, the goals, policies and recommendations of this report have been grouped under one of the three actions requested of the Board of Supervisors by this report. Thus, each recommendation in this report that TAC advocates the Board of Supervisors adopt is related to the policies and goals of the TCWMP add related to the Board actions requested.
A reference number identifies the report section where the recommendation may be found along with supporting discussion. A complete list of the recommendations made in this study is given in Appendix G.
ACTION I: Adopt a Topanga Creek Watershed Management Plan
GOAL 1: To improve public safety and protect existing life, infrastructure, and property from flood hazards
GOAL 4: To preserve and protect the creek environment
PolicyRecommendation1.1 Ensure that no existing life and property be placed at risk from hazards created by increases in peak flow runoff produced by new developmentA3.3-1
A3.3-2
A3.4.2-1
A2.1-1
A2.2.2-1
A2.3-1A2.4-2
A2.6-1
A3.2-1
A3.4.2-1
A3.4.2-2
A3.4.2-3A3.5.2-1
A3.5.2-3
A3.5.2-3
A3.5.3-1
A3.5.3-2
C1.1.1-21.2 Reduce the flood hazard by implementing measures to reduce existing peak flow runoffA3.3-1
A3.3-2
A3.4.2-1
A2.1-1
A2.2.2-1
A2.3-1
A2.4-2
A2.6-1
A3.2-1
A3.4.2-1
A3.4.2-2A3.4.2-3
A3.5.2-1
A3.5.2-3
A3.5.2-3
A3.5.3-1
A3.5.3-2
C1.1.2-1
C1.1.2-2
C1.1.2-4
C1.1.2-5
C1.1.3-1C1.1.3-2
C1.1.3-3
C1.1.3-4
C1.1.3-5
C1.1.3-6
C1.1.3-10
C1.2-1
C1.3-1
C1.3-2
C1.3-31.3 Evaluate existing risks to public safety and develop programs to address themA3.5.2-1
C1.3-3
C1.3-7
C1.3-8
C1.3-9
C1.4-1C2.2-3
C2.2-4
C2.2-12
C2.2-13
C4.0-1
C5.1-1 to
C5.1-11
C5.6-1
C5.6-2
C7.0-2
C7.0-31.4 Regulate new development in the riparian zone to prevent increases in flood damageA3.3-1
A3.3-2
A3.4.2-1
A2.1-1
A2.2.2-1
A2.3-1
A2.4-2
A2.6-1
A3.2-1
A3.4.2-1
A3.4.2-2
A3.4.2-3A3.5.2-1
A3.5.2-3
A3.5.2-3
A3.5.3-1
A3.5.3-2
A3.5.2-1
A3.5.2-3
A3.5.2-3
A3.5.3-1
A3.5.3-2
C1.1.2-1
C1.1.2-2
C1.1.2-4
C1.1.2-5
C1.1.3-1
C1.1.3-2
C1.1.3-3
C1.1.3-4
C1.1.3-5
C1.1.3-6
C1.1.3-10
C1.2-1
C1.3-1
C1.3-2
C1.3-34.1 Preserve and rehabilitate the stream channel and floodplains to restore natural channel capacity wherever feasible.
C1.3-1
C1.3-2
C1.3-4
C6.2-1C6.4-3
C7.1-14.2 Protect the riparian habitat which plays a crucial role in intercepting rainfall, reducing stormwater runoff, maintaining slope stability, and allowing for greater groundwater recharge.
A3.3-1
A3.3-2
A3.4-1
A3.5-1
A3.5.3-1
C1.1.3-1C1.1.3-5
C1.3-4
C2.2-2
C2.2-3
C6.3-1
C6.3-1
C6.3-3
C6.4-1C6.4-2
C6.4-3
C6.5-3
C6.5-3
C6.5-4
C6.6-1
C6.8-1
C6.9-14.3 Improve and protect water quality by reducing erosion, sedimentation, point and non-point source pollution.
C2.2-11
C5.0-1
C5.0-2
C5.0-3
C6.10-1
C7.1-1
ACTION II: Establish the Topanga Creek Watershed Management Committee
GOAL 2: To establish a Watershed Management Committee (WMC) as a permanent administrative body to implement, monitor and coordinate the Topanga Creek Watershed Management Plan (TCWMP)
GOAL 3: To provide a community based educational forum regarding Best Management Practices that reduce flood hazards
This Committee should be composed of private citizens, and public agencies with an interest in the Topanga Creek Watershed.
The RCD of the SMM should be the lead agency, with LA County representatives from DPW, Fire Dept., Regional Planning. Non- County agency representatives of Caltrans, all utilities, Coastal Commission, Fish and Game, State and National Park services should also participate.
PolicyRecommendation2.1 Coordinate Federal, State, and County regulations to provide a comprehensive integrated management planA3.1.3-1
A3.2-1
A3.4.2-2
A3.5.2-3C1.2-1
C1.4-1
C2.1-12.2 Require agencies and utilities to adhere to the same guidelines and regulations as non-governmental agencies and citizensA3.5.2-22.3 Define the flood hazard problem in terms of potential harm to people, structures, and the stream course/riparian habitatA3.3-2
A3.5.2-1
A3.5.3-1
A3.5.3-2
A3.5.4-1
A3.5.4-2
C1.1.1-1C1.1.1-2
C1.1.3-6
C1.3-1
C1.3-8
C1.3-9
C2.2-1 to
end of C2.4 Encourage all property owners in the watershed to contribute to flood hazard mitigationA3.4.2-2
A3.5.2-2All rec.
in C3.1 Develop an outreach program to inform residents of flood hazards and ways to protect themselvesC5.1-1 to C5.1-11
3.2 Provide a community forum for education regarding Best Management Practices which can reduce the flood hazardA2.1-1
A2.1-2
A2.2.1-1
A2.2.1-2A2.2.2-1
A2.3-1
C5.1-1 to
C5.1-113.3 Provide a cooperative forum encouraging coordination voluntary efforts to minimize the flood hazardC5.1-1 to C5.1-11
3.4 Provide a funding mechanism to support construction of necessary flood hazard mitigationsC1.1.2-4
C1.1.3-7C4.0-3
C6.0-1
C8.0-1
ACTION III: Implementation of the Topanga
Creek Watershed Management Plan
Actions
RecommendationRescind Floodways in Topanga
A3.4.2-2Annex the TCWMP to the State FHMP
A3.2-1Perform CRS points analysis
A3.5.2-3Validate Topanga hydrologic model
C1.1.1-2Coordinate with other watershed management plans
C1.4-1Implement land use policies
C1.2-1Make assessment of existing bridges
C1.3-1
REFERENCES
ìAn Alternative Plan To The Proposed Topanga Canyon Floodway Ordinance î, Topanga Canyon Floodplain Management Citizensí Advisory Committee, Sept. 17, 1992.
ìHydrology and Sedimentation Manualî, Los Angeles County Department of Public Works, Dec. 1990.
Dracup, John, ìA Hydrologic Evaluation of the Proposed Topanga Canyon Floodway Ordinanceî, Sept. 4, 1991.
Malibu Creek Watershed Natural Resources Plan, Soil Conservation Service, June 1992.
Bidol-Padva, P and B. Breenword, ìComprehensive Malibu Creek Watershed Mediation Effort, Final Reportî, May 1994.
Proposed Malibu City Ordinance 51U, Feb. 1994.
Abstracts from the Floodplain Management Association, March 29-31, 1995.
Proceedings of the Southern California Watershed Conference, Making Watersheds Workî, Burbank Hilton, September 21, 1995.
Staff Report 4-95-123, California Coastal Commission, Nov. 1995.
Design Guidelines for flood Damage Reduction, FEMA-15, Federal Emergency Management Agency, Dec. 1981.
ìTechnical Appendices of the Environmental Impact Report for Canyon Oaks Developmentî, Michael Brandman Associates, December 1992.
ìSupplemental Environmental Impact Report for Canyon Oaksî, Michael Brandman Associates, July 1993.
Personal communication with DWR/FEMA representative, January 1996.
Thomas, Frank H., (of FEMA), "River Corridor Management and the National Flood Insurance Program", Multi-Objective River Corridor Management, Proceedings of the Urban Stream Corridor and Stormwater Management Workshop, March, 1989.
Topanga Canyon Creekside Homeowners' Association (TCCHA) Position Statement.
Testimony of Dr. John A. Dracup, concerning the runoff from the Canyon Oaks Property, February 10, 1994.
Summit Pointe correspondence between the County and TCCHA.
ìModel Floodplain Management Ordinance for California Communitiesî, prepared by the Flood Loss Reduction Section, Division of Flood Management, Department of Water Resources, State of California, July 1992.
Dracup, John A., ìA Critical Evaluation of the Drainage Plan for the Canyon Oaks Development and the Upper Topanga Canyon Drainage Policyî, February, 1994.
ìAction for Bay Restoration, Santa Moncia Bay Restoration Planî, Santa Monica Bay Restoration Project, March 1994.
ìDraft of Waste Discharge Requirements for the Discharge of Storm Waterî, California Regional Water Quality Control Board, Los Angeles Region, December 1995.
Raphael, M., J. Feddema, A. Orme, and A. Orme, ìThe Unusual Storms of February 1992 in Southern Californiaî, Phycial Geography, 1995.
NPS testimony from the ìFinal Environmental Impact Report for Canyon Oaksî, Michael Brandman Assocaites, December 1993.
The Topanga Story, Louise York (editor), The Topanga Historical Society, 1992.
Santa Monica Mountains Comprehensive Plan, August 1979.
Malibu/Santa Monica Mountains Interim Area Plan, Los Angeles County Department of Regional Planning, 1981.
Malibu Local Coastal Program Land Use Plan, 1986.
Radtke, K. 1983. Living More Safely in the Chaparral-Urban Interface. PSWFES Gen. Tech. Rept. PSW-67.
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