Old, Grand Prix, and Padua Fires (October, 2003) Burn Impacts to Water Systems and Resources
Total Page:16
File Type:pdf, Size:1020Kb
Old, Grand Prix, and Padua Fires (October, 2003) Burn Impacts to Water Systems and Resources Santa Ana River Watershed Area San Bernardino National Forest, California Prepared for: Burn Area Emergency Response (BAER) Team U.S. National Forest Service Santa Ana Watershed Project Authority 11615 Sterling Avenue Riverside, CA 92503 (909) 354-4224 www.sawpa.org November 10, 2003 (Revised December 5, 2003) SUMMARY The Santa Ana Watershed supplies most of the drinking water for over 5 million of the Watershed’s residents. Rainfall in and around the San Bernardino, San Gorgonio and San Jacinto Mountains’ forest areas, provides surface water flows and groundwater recharge throughout the region via the Santa Ana River and its tributaries. Recent fires in these areas were large and difficult to contain and the aftermath of these fire events have resulted in extraordinary impacts on the forest and the Watershed. The recent Grand Prix, Old and Padua Fires burned over 120,000 acres (more than 185 square miles) of wild land habitat in the Santa Ana Watershed, primarily within the San Bernardino National Forest. These fires will have significant impacts on the Santa Ana River and its associated water quality for an extended period and will impact areas far from the burned sites. It is estimated that the fires’ effects will impact an additional 430 square miles of the Watershed. In sum, Burned Mountaintop the recent fires will impact one-quarter of the Watershed and without intervention most of the associated costs will be borne by local government. The purpose of this summary is to document the likely impacts to water supply, quality, habitat Issues Summary and flood control throughout the Watershed resulting from the Grand Prix, Old and Padua Fires. The · Severe fire in area information contained herein is intended to provide providing drinking water for over 5 million people background and support for the United States Forest Service (USFS) Burn Area Emergency Response · Water resources already (BAER) Team. Upon review by the BAER Team, this reduced by drought summary will intend to inform and aid decision makers · Sediment, ash and debris and other interested parties throughout the Watershed. will flow out of burn areas and damage infrastructure Fuel loads in the San Bernardino National Forest and · Impacts will occur in adjoining areas are extraordinarily high due to forest burned areas and and private property management practices in these downstream urban forest areas. Estimating the water quality impacts · Mitigation costs cannot be after a large burn across these fuel-laden areas is borne by cash-strapped difficult, but research by SAWPA indicates that the local governments Santa Ana Watershed is at risk if winter rains are average to heavy. SAWPA staff reviewed the U.S. Bureau of Land Management (BLM) Forest Service Environmental Impact Reports for controlled burn management, Forest Service research publications, Los Angeles County Flood Control plans, impact history from the Heyman fire in Colorado, and personal communications with Riverside Fire Lab personnel. - 1 – Although recent analysis has focused on fire effects within the burn area and areas directly adjacent, much of the impacted infrastructure will be far from the burn areas and located in the heavily populated valleys. Infrastructure needs within the Santa Ana Watershed were identified in 1999, as part of the development of an Integrated Watershed Program (IWP). SAWPA was directed by the five largest water districts in the region to develop and implement a plan to ensure sufficient clean water to entirely support watershed needs, presently and in the future. To prepare for greater water demands, projected to increase nearly 30% within 20 years, and seeking to drought proof the region so that no imported water would be required during drought years, SAWPA developed a 10-year IWP to Flood Control Channel Downstream of Fire address regional needs. Over 200 water resource-related projects were identified as part of this program to date. Three billion dollars were estimated to implement the 10-year IWP. In 2000, SAWPA successfully contracted with the State Water Resources Control Board to use $235 million in Proposition 13 Water Bond funds to begin construction of over 800 million dollars in projects, directly supporting the IWP. Costs borne by local agencies in response to problems arising from recent fire events will significantly impact the ability of cooperating agencies to implement the SAWPA IWP. Therefore, efforts to reduce the region’s dependence on imported water will be drastically impacted and consequently, will have a lasting impact on water supplies statewide. Costs of mitigating the effects of recent fires within the Watershed are estimated to be near $450 million, and are summarized below: Fire Impact Cost Estimates Impact Type Total Cost First Year Sediment Removal (5 years) $ 125,250,000 $12,525,000 Flood Control Improvements (56 basins) $ 56,000,000 $5,600,000 Basin Percolation Restoration (25 basins) $ 6,250,000 $1,250,000 Habitat Restoration (7,500 acres) $ 15,000,000 $1,500,000 Toxic or Radiological Treatment $ 13,000,000 $500,000 Inorganic Salt Removal (Capital and 20 yrs. Op) $ 182,000,000 $18,200,000 River and Basin Quality Monitoring $ 8,850,000 $1,770,000 Water Supply Emergency $ 35,350,000 $3,535,000 Wetland Restoration (2,500 acres) $ 5,000,000 $500,000 TOTAL $446,700,000 $45,380,000 - 2 – In addition, local water agencies have expressed concern over the direct infrastructural damage to wells, access roads and other infrastructures resulting from increased debris and sediment flow from storm events following the fires. Although the fires did not burn every area anticipated in Recent Fires Will Increase earlier calculations, impacts are likely to be severe over five Levels of: or more years, depending on rainfall and storm intensity. · Sediment/Silt The estimated cumulative cost to the Watershed is estimated to be greater that $800 million, not including fire damage to · Contaminants homes and habitat. In addition, much of the unburned area is · Salts still at extreme risk for catastrophic fire. In the future, costs · Ash are likely to be higher than those projected from the recent fire events. Anticipated Effects to the Watershed from Recent Fire Events The Grand Prix, Old and Padua fires of October and November of 2003, burned over 185 square miles of the front country, urbanized facing slopes, in the San Bernardino National Forest and adjacent lands. Fire damage was limited in the mountainous upper watershed containing high populations of pine trees suffering mortality from drought and bark beetle infestation. Approximately three percent or 3,600 acres of the standing timber impacted by the bark beetle burned in this fire. Much of the area burned by the fire was located in the mountain foothills and consisted of invasive, exotic grasses and inland coastal sage scrub habitats. Discussion with local water agencies identified the following areas of risk to the Grand Prix Fire Watershed associated with the October and November 2003 fires: 1. Water Quality and Supply Impacts; 2. Habitat and Endangered Species Impacts; and 3. Flood Control Impacts. Each area will be discussed more thoroughly in subsequent sections. - 3 – INTRODUCTION This section provides an overview of the existing geologic and hydrologic features, and ecological features of the Watershed. Existing Geologic, Hydrologic, and Ecological Features of the Santa Ana Watershed The upper watershed or headwaters, including the highest point in the drainage system, is delineated by the east-west ridgeline of the San Gabriel and San Bernardino Mountains (Fig. 1). Over this ridgeline lies the Mojave Desert, which is part of the Lahontan Basin. This upper “erosion” zone of the Watershed has the highest gradient, highest erosion level of new sediment to the system, and fastest stormwater runoff. As flows consist mainly of snowmelt and storm runoff from the undeveloped land in the San Bernardino National Forest, water quality tends to be high, with low concentrations of total dissolved solids, nitrates, and other pollutants. In this zone, the Santa Ana River (River) channel is confined in its lateral movement, contained by the slope of the high, mountainous terrain. Within the upper watershed, the River and its tributaries travel around large boulders and over sand and gravel bars punctuated by pools and riffles reaching depths of approximately six feet. Sedimentary and crystalline materials from the upper watershed move down slope through a process fed by storm pulses; therefore, sediment does not move at a continuous speed. River flow from Seven Oaks Dam to the City of San Bernardino consists mainly of storm flows, flows from the Lower San Timoteo Creek, and groundwater that is rising due to local geological features. From the City of San Bernardino to the City of Riverside, the River flows perennially and much of the reach is operated as a flood control facility. The principal tributary streams in the upper Santa Ana Watershed originate in the San Bernardino and San Gabriel Mountains. From the City of Riverside to the recharge basins downstream from Imperial Highway, River flow, under non-storm conditions, consists of highly treated Publicly Owned Treatment Works (POTW) effluent, urban runoff, irrigation runoff, imported water applied for groundwater recharge, and groundwater forced to the surface by underground barriers. Near Corona, the River cuts through the Santa Ana Mountains and the Puente-Chino Hills, which together form the northern end of the Peninsular Ranges in Southern California. The River then flows onto the Orange County coastal plain where the channel lessens in gradient, the Burn Area, San Bernardino Mountains valley floor is reached, and the soft features of the channel where sediment has deposited is more prevalent. Floodplains are strewn with boulders and characterized by sand and gravel washes. - 4 – The Orange County coastal plain is composed of alluvium derived from the mountains.