FIELD AND ANALYSIS PARTICIPANTS

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1 Natural Resources Conservation Service Jonas Feinstein: State Office Denver Federal Center Building 56, Room 2604 PO Box Denver, CO SUBJECT: Damage Survey Report DATE: May 20, 2012 Post-fire Evaluation, Erosion Risk and Hazard Assessment for the Lower North Fork Fire near Conifer, Colorado TO: Joseph Hansen, Conservation Forester, Jefferson Conservation District Karen Berry, Geologic Engineer, Colorado Geological Survey Boyd Byelich, District Conservationist, NRCS Don Kennedy, Environmental Scientist, Denver Water Kate Newman, Assistant County Administrator, Jefferson County John Andrews, State Engineer, NRCS CC: Phyllis Phillips, State Conservationist, NRCS Eugene Backhaus, State Resource Conservationist, NRCS Boyd Byelich, District Conservationist, NRCS Rachel Murph, State Rangeland Specialist, NRCS Christine Taliga, State Plant Material Specialist, NRCS Terri Sage, State Biologist, NRCS Ron Schierer, Area 2 Resource Conservationist, NRCS Jim Sharkoff, State Agronomist, NRCS Rich Edwards, Assistant Staff Forester, CSFS FIELD AND ANALYSIS PARTICIPANTS John Andrews, State Engineer, NRCS Joseph Hansen, Conservation Forester, Jefferson Conservation District Jonas Feinstein, State Forester, NRCS Al Albin, State Geologist, NRCS Boyd Byelich, District Conservationist, NRCS Ron Schierer, Area 2 Resource Conservationist, NRCS Brian Devine, Watershed Coordinator Jefferson Conservation District Kaitlin Fischer, Community Coordinator, Jefferson Conservation District Jonathan Geurts, WAE, NRCS Rachel Murph, State Rangeland Specialist, NRCS Christine Taliga, State Plant Material Specialist, NRCS Terri Sage, State Biologist, NRCS

2 SUMMARY On March 26, 2012, the Lower North Fork Fire began on a forty acre prescribed fire unit of Denver Water lands in which firebrands were transported by high winds to receptive fuels outside of the containment/mop-up line, four days after the prescribed fire took place. The fire burned about 4 miles from the center of Conifer, and 10 miles from the city of Littleton. The fire burned 4140 acres in very rugged terrain with a high degree of variation in vegetation, topography, and resulting burn severities. Three fatalities and Figure 1: Landscape position of the Lower North Fork Fire relative to towns and major rivers NRCS Colorado State Office 2 of 27 May 20, 2012

3 twenty-seven structures were lost, total losses were initially estimated at approximately $11 million dollars. The fire was 100% contained by a multi-agency effort seven days later on April 2, The Jefferson Conservation District requested in writing to Jefferson County commissioners, that the Conservation District act as the sponsor of a potential Emergency Watershed Protection request, and thus requested that the Natural Resources Conservation Service provide technical and if possible financial assistance to identify and mitigate post fire risks and hazards associated with post-fire erosion hazards to life, property, and infrastructure. On April 5, 2012, a survey team consisting of a local community liaison, Natural Resources Conservation Service, Denver Water, Jefferson Conservation District, Jefferson County, and Colorado State Forest Service personnel were on hand to assess the immediate post fire conditions, and make initial determinations of post fire risk, hazards, and values at risk, with potential recommendations for mitigating identified risks. It was determined through this analysis, field observations, and partner meetings that the need for post fire Emergency Watershed Protection exigency and regular emergency funds were unwarranted at this time. The assessed hazard of post fire erosion weighted with the likelihood (or risk) of debris reaching values at risk did not justify the use or potential request of Emergency Watershed Protection funding at this time. However, this report intends to also address several site specific actions that landowners may take to address small scale erosion, hazard tree, and rehabilitation efforts on their respective properties. NRCS Colorado State Office 3 of 27 May 20, 2012

4 The field assessments and this resulting document focus on two primary objectives with associated subcategories Resource Assessment & Risk Assessment: 1. Resource Assessment and Analysis I. Drainage Basin Characteristics (a) Sub-basin Characteristics (b) Topography and Landform (c) Landownership and Boundaries II. Vegetation & Hydrologic Characteristics (a) Before and After the Lower North Fork Fire III. Soils & Geology Assessment (a) Soil Types & Geology (b) Erodibility (c) Surface Rock Fraction (d) Hydrologic Soil Group IV. Burn Characteristics (a) Burn Area Reflectivity Classification (BARC) (b) Soil Burn Severity Mapping (c) Field Observations (d) Soil Burn Severity Summary V. Various Assessment Products (a) Sediment Erosion Potential (ERMiT and WEPP) 2. Risk Assessment and Analysis I. Identification of Values at Risk (a) Transportation, (b) Utilities & Water Infrastructure (c) Residential Properties (d) Commercial & Business Property (e) Public Property (f) Endangered Species (g) Cultural Resources II. Analytic Products & Synthesis (a) Mapping and Model integration in the context of the values at risk III. Post Fire Rehabilitation and Hazard Mitigation Recommendations (a) Emergency Watershed Protection Program Recommendations (b) General Recommendations for Hazard Mitigation, and Land Rehabilitation NRCS Colorado State Office 4 of 27 May 20, 2012

5 1. RESOURCE ASSESSMENT AND ANALYSIS I. DRAINAGE BASIN CHARACTERISTICS (a) Sub-basin Characteristics The burn perimeter was located in four minor drainage basins that flow into either the North Fork or Main stem of the South Platte Rivers (See figure 1 and 2). These drainages are Long Gulch (includes Elkhorn Gulch) in the western 2/3 of the fire area, Willow Creek on the eastern 1/3 of the fire area, Bear Gulch found north of the burn perimeter, and a small unnamed watershed located in the southwest corner of the burn where the escaped prescribed fire originated from. Concerns for post fire watershed and soil stability were initially focused on both Willow Creek and Long Gulch. The initial site visit on April 5th, revealed that Bear Gulch, the unnamed watershed Figure 2: Minor Drainage systems of the Main and were not of concern. Similarly, it was North Fork of the South Platte Rivers (dark blue and also determined that Willow Creek did aqua blue respectively), including Long Gulch and Elkhorn Gulch (light yellow), Willow Creek not pose a threat to life, property, and (orange), an unnamed drainage (brown) and Bear infrastructure that warranted further Gulch (dark yellow) concern for immediate exigency or regular emergency mitigation of post fire hazards. Therefore, the focus of this assessment would be for the remaining 2/3 of the fire in the Long Gulch drainage (See Figure 2). Sub-watershed Willow Creek Long Gulch Elkhorn Gulch Un-named Watershed Area 2049 acres 1417 acres 1110 acres 388 acres Area Burned 705 acres (34%) 955 acres (67%) 1030 acres (93%) 349 acres (90%) Average Gradient and Length to South Platte Rivers 8% over 11,824 feet 7% over 15,477 feet 13% over 12,145 feet 11% over 6,934 feet Table 1: Minor watersheds area, proportion burned, average stream gradient and length NRCS Colorado State Office 5 of 27 May 20, 2012

6 Approximately 2000 acres burned in Long Gulch and its tributaries. Of the that almost 2000 acres, Long Gulch proper was 67% burned and its tributary Elkhorn Gulch was 93% burned. Long Gulch proper to the west has a 7% gradient over almost three miles from the bottom of the steep incline at its headwaters to the North Fork of the South Platte River. Elkhorn Gulch to the east of Long Gulch has a wider upstream catchment with the similar acres, of interest in this case, it that the gradient is 13% over a 2.3 mile distance to the confluence with Long Gulch. (a) Topography and Landform Topography and terrain features are very rugged and variable, ranging from relatively broad and flat hill tops and ridgelines with very steep and sometimes narrow drainages. Slopes within the burn perimeter averaged about 40% with a range from 0-365%. Long Gulch and ElkHorn Gulch represent the largest catchment with the most acres burned in addition to the variation in topography. Figure 3: Percent Slope. Black increasing to white connotes flat to very steep conditions in percent slope % = 0-65 degrees NRCS Colorado State Office 6 of 27 May 20, 2012

7 (b) Landownership and Boundaries The Lower North Fork Fire burn perimeter is approximately 4020 acres, with the following approximations for ownership and acres within the burn perimeter (Figure 4): Private Lands: The majority of the private lands found in the burn perimeter were129 parcels for 2804 acres, or about 70% of the burn area Denver Water Lands: 16 parcels for 1039 acres, or about 26% of the burn area Jefferson County Open Space: 8 parcels for 177 acres, or about 4% of the burn area USDA Forest Service: 1 parcel for 0.4 acres Figure 4: Landownership: green; private lands, light blue; Denver Water lands, yellow; Jefferson County Open Space, and red; USDA Forest Service lands NRCS Colorado State Office 7 of 27 May 20, 2012

8 II. VEGETATION AND HYDROLOGIC CHARACTERISTICS (a) Before and after the Lower North Fork Fire The high degree of topographic and landform variation within and among the surrounding landscape produces a high degree of variation in ecological plant and animal communities. Warm and dry southern aspects are populated with a grass, forb, shrub plant community comprised of mountain shrubs, mountain mahogany, currents, Rocky Mountain juniper, and Gambel oak, seasonal and perennial grammanoid and forb species. Drainages and protected areas in this area of the burn provide conditions to support trees which are predominately ponderosa pine and Douglas-fir. The higher elevation sites within the burn area are indicative of a transitional dry/wet mixed conifer, comprised of aspen, ponderosa pine, Douglas-fir, Colorado blue spruce, and occasional lodgepole pine. Lower elevation drainages and protected sites can produce very large Colorado blue spruce and ponderosa pine, with willows and rocky mountain maple and alder found in drainages. In open meadows and valleys, smooth brome and alfalfa was observed. Per the Colorado Natural Heritage Program and its identification of Potential Conservation Areas (PCA), and no identified species and or plant/animal communities at risk as of a result of post-fire erosion from the Lower North Fork Fire. Post fire vegetation effects, were as variable as the topography and resulting vegetation mosaic. The fire exhibited a high degree of mixed severity, even under what was described as elevated fire behavior. The fire produced a predominately low severity outcome, though in instances where a high density trees in conjunction with topography (such as natural chimneys and steep slopes) produced high severity outcomes. High severity as it relates to overstory mortality in trees and shrubs in this particular fire could be characterized by two outcomes, complete mortality and overstory mortality. In the case of complete mortality, it is expected that all conifers that were either scorched of 60% of the tree or fully consumed will die. Shrubs such as mountain mahogany and Gambel oak and aspen will generally vegetatively regenerate from intact root systems following a fire. Site visits after the fire confirm that vegetative recovery has begun in earnest. Grammanoid and forb NRCS Colorado State Office 8 of 27 May 20, 2012

9 IV. SOILS AND GEOLOGY (a) Soil Types and Geology Twenty soils are represented within the fire perimeter. Most soils exist as complexes and are representative of highly variable landform and topographic features resulting in spatially heterogeneous soil conditions and mixtures thereof. Of the twenty soils mapped within the burn perimeter, four soils accounted for about 2/3 of the total area. 3 - Allens Park variant-ratake-rock outcrop complex, 30 to 50 percent slopes, accounting for about 10% (311 acres) of the burn area 55 - Grimstone-Hiwan-Rock outcrop complex, 30 to 60 percent slopes, accounting for 6% (198 acres) within the burn area Ratake-Cathedral-Rock outcrop complex, 25 to 60 percent slopes, which account for 35% (1078 acres) found in the burn perimeter Rogert-Herbman-Rock outcrop complex, 30 to 70 percent slopes, which accounts for 11% (347 acres) of the burned area. All soils, with exception to 16 acres, represented within the burn unit are considered sandy, very sandy, or gravelly loams. Generally speaking all soils represented within the burn perimeter are well drained, poorly developed, and are relatively shallow to bedrock. Soils found on ridgelines and high points, in addition to being found adjacent to rock outcroppings typically are the shallowest to bedrock, with valleys, drainages, and benches are better positioned to accumulate and develop soil. Figure 4: Soils and soil burn severity of the Lower North Fork Fire: Green polygons with bold numbers represent soil MU (Map Unit) that corresponds to the Golden Soil Survey, NRCS A significant portion of the area has rock outcroppings and boulders. This geomorphology has consequences associated with erosion potential and concentration and velocity of storm runoff. NRCS Colorado State Office 9 of 27 May 20, 2012

10 What makes this fire unique to the South Platte Basin is the geology that it is located on. The fire perimeter straddles a fault on the lower 25% of the burn perimeter, and thus is separated into two distinct geologies resulting in different soil parent materials. What makes this particularly interesting is that the expected erosion typical of the South Platte basin may not be a factor in this particular fire. The Pikes Peak batholithic granite predominates much of the region to the south of this burn, where as a Precambrian biotite gneiss dominates the landscape to the north 75% of the burn. Figure 5: Geology and soil burn severity of the Lower North Fork The observed result in Fire: Light Green; Biotite Gneiss, Purple; Batholith Granite. landform, site productivity, and erosion potential is significant. (b) Erodibility Factors controlling soil erosion, in this case, primarily water, resulting in rill and gully erosion, are 1) energy to dislodge soil particles, 2) volume to transport soil particles, and velocity and concentrated flow of water to incise and carry mass flow of sediment in solution. Combinations of slopes within the burn area are typically steep (average of 40%), and soil development and depth to bedrock poor and shallow respectively. Given the severity of typical high severity burn areas would show that the lack of soil structure, protection, and presence of water impervious layers would suggest that this landscape in the case of moderate to high severity is highly likely to produce highly erosive slopes. In conjunction with the very narrow drainages and draws, concentrated flows would be expected and volume estimates should be developed to assess potential for sediment to be transported. NRCS Colorado State Office 10 of 27 May 20, 2012

11 (c) Surface and Soil Rock Fraction Surface rock fraction and the associated soil rock fraction are highly variable based on the complex nature of the mapped soils, the ubiquitous presence of rock outcrops and the variable terrain. To that effect, it is noted that in rock outcrops the acres subcatchments may be covered with as much as 50% of rock, in other areas only 10%. Within the soil matrix, any given soil pedon within the complex will be highly variable as well, soil descriptions can elude to the percent rock/coarse fraction that is present in the soil matrix. They are as follows; <15%: No Adjectival or modifying terms 15-35%: The adjectival term of the dominant kind of rock fragment is used (Gravelly loam, channery loam, cobbly loam) 35-60%: The adjectival term of the dominant kind of rock fragment is used with the word very (Very gravelly loam, very flaggy loam) >60%: If enough fine earth is present to determine the textural class the adjectival term of the dominant kind of rock fragment is used with the word Extremely (extremely gravelly loam, extremely boulder loam) (d) Hydrologic Soil Group The identified representative hydrologic soil groups for the soils within the burn perimeter are all within the Hydrologic Soil Group D, These soils are as defined - Soils in this group have high runoff potential when thoroughly wet. Water movement through the soil is restricted or very restricted. Group D soils typically have greater than 40 percent clay, less than 50 percent sand, and have clayey textures. In some areas, they also have high shrink-swell potential. All soils with a depth to a water impermeable layer less than 50 centimeters [20 inches] and all soils with a water table: 3 - Allens Park variant-ratake-rock outcrop complex, Hydrologic Soil Group D, accounting for about 10% (311 acres) of the burn area 55 - Grimstone-Hiwan-Rock outcrop complex, Hydrologic Soil Group D, accounting for 6% (198 acres) within the burn area Ratake-Cathedral-Rock outcrop complex, Hydrologic Soil Group D, which account for 35% (1078 acres) of the soils found within the burn perimeter Rogert-Herbman-Rock outcrop complex, Hydrologic Soil Group D, which accounts for 11% (347 acres) of the burned area. NRCS Colorado State Office 11 of 27 May 20, 2012

12 Hydrologic condition Hydrologic soil condition Poor Fair Good Soils have a low runoff potential due to high infiltration rates. These soils consist primarily of deep, well-drained sands and gravels Soils have a moderately low runoff potential due to moderate infiltration rates These soils consist primarily of moderately deep to deep, moderately well- to welldrained soils with moderately fine to moderately coarse textures. Soils have a moderately high runoff potential due to slow infiltration rates. These soils consist primarily of soils in which a layer exists near the surface that impedes the downward movement of water or soils with moderately fine to fine texture. Soils have a high runoff potential due to very slow infiltration rates. These soils consist primarily of clays with high swelling potential, soils with permanently high water tables, soils with a clay pan or clay layer at or near the surface, and shallow soils over nearly impervious parent material. Table 2: Generalized Curve Number table (CN) for various forest soils and the respective management. Poor: forest litter, small trees, and brush are destroyed by heavy grazing or regular burning. Fair: forests are grazed, but not burned, and some forest litter covers the soil. Good: forests are protected from grazing, and litter and brush adequately cover the soil. Taken from Robichaud et al Modified from: ISU 2008, Table 4, p. 9. Willow Creek and Long Gulch only provide large enough catchments to likely support a ephemeral stream. Though it could on wet years provide evidence of being a perennial stream with the presence of willows, Rocky Mountain maple and alder. The soils in the burn area and surrounding landscape are defined more by, sandy, very sandy, or stony loams than any other soil group. This soil texture and rock fraction characteristic has implications for hydrologic function as soils are generally characterized as well drained. Curve numbers reflecting soil hydrologic functional groups by soil texture, and the associated expected infiltration rate. The curve number is a quantitative number associated with the condition of the vegetative cover, soil type, and can be based on management associated with primarily, agricultural uses, grazing and/or to a lesser degree fire (table 2). NRCS Colorado State Office 12 of 27 May 20, 2012

13 V. BURN CHARACTERISTICS (a) Initial Burn Severity In anticipation of the need to conduct a post fire erosion risk and hazard assessment, NRCS requested a Burn Area Reflectance Classification (BARC) map from the USFS Remote Sensing Applications Center (RSAC), and their Rapid Disturbance Assessment Services Department. The first of the BARC maps was delivered on March 30th; this map was generated from LANDSAT 7 imagery that provided only a 50% coverage and analysis of burn severity. An additional map was generated to better fill-in gaps with another LANDSAT 7 flyover a week later, this updated map was delivered April 8th and had 80% coverage. The burn took place in two predominate sub watersheds of the Figure 6: Final Burn Area Reflectance Classification (BARC) lower north fork of the South Platte, Map, April 08, 2012 USDA USFS Remote Sensing Application Center. No color indicates unburned/no-data, blue: low Willow Gulch and Long Gulch. severity, orange: moderate severity, and red: high severity The BARC remotely sensed data is classified in a continuous 265 reflectance analysis, with distinct breaks delineating unburned/no data, low severity, moderate severity, and high severity. This data is intended to be changed to serve as a preliminary guide to soil burn severity. (b) Soil Burn Severity On five separate occasions, with a combination of NRCS State and Field Office, Jefferson Conservation District, Denver Water, and USFS RMRS personnel surveyed and ground rectified burn severity maps to determine soil severity based on the initial BARC maps. It was determined the BARC map was very good at determining overstory mortality. As such, there is typically a reasonably good correlation between overstory burn severity and resulting soil burn severity. However, in this particular burn, it was determined that given the fire behavior, the existing vegetation, topography, and season of the burn, that overstory burn severity be decoupled from soil severity. NRCS Colorado State Office 13 of 27 May 20, 2012

14 Soil Burn Severity is the formal process of rapidly assessing the Burn Area Reflectance Classification on the ground, and providing guidance to managers to assess where potential post fire erosion hazards exist. It should be noted that this map is intended to be consistent with ground truthed assessment of severity of post fire soil conditions (Annette Parson et al. 2010) related to the following: 1) amount and condition of ground cover, 2) depth and color of ash, 3) presence and degree of soil structure, 4) amount and type of intact root structure, and 5) evidence and depth of soil repellency. There is a significant disparity from the initial April 8th BARC map, and resulting burn severity classifications and this soil burn severity classification map. The disparity between the two maps is likely a result of the modification of the key assumption of high density Figure 7: Final Soil Burn Severity Assessment based from the Map, April 08, 2012 USDA USFS Remote Sensing overstory mortality (BARC) Application Center. No color indicates unburned/no-data, blue: corresponding well to low severity, orange: moderate severity, and red: high understory soil severity. We severity believe that two factors played a critical role in this outcome, 1) fire behavior, and 2) the time of year (early spring). These two factors were the primary contributors to modify the normal expectation that high severity (mortality) corresponded to high soil burn severity. Fire behavior and seasonality are small and significant details, and serve as the explanation of the primary trend across the entire burn area, and we believe that is primarily attributed to the high surface fuel moisture found in the litter/duff layer, and upper organic horizons of the soil profile. Also, mortality in trees was typically very high, even in the case of scorched trees, and we believe this is attributed to again the NRCS Colorado State Office 14 of 27 May 20, 2012

15 seasonality of the burn, as the trees were just beginning to respire and come out of dormancy. In dormancy, trees desiccate and reduce water and/or have more carbohydrates in solution to avoid freezing and bursting cell structure over the winter. In this case, the lack of water and fuel moisture in the canopy may have contributed to the very rapid spread and growth of the fire, in addition to the already hot and windy conditions that the fire escaped under, even though the ground was still relatively wet.. The departure is found primarily in the increase in the amount of low severity at the expense (or decrease) of high severity and moderate severity classifications. The differences are captured in table 3. Burn Classification Initial BARC Map Soil Severity Map (4/10/2012) (5/18/2012) Unburned/No Data classes Low Severity classes Moderate Severity classes High Severity classes Table 3: Classification breaks between the BARC April 10, 2012 map and the Soil burn severity map of May 18, 2012 map. (c) Field Observations From the first site visit on April 5 th, 2012 to a most recent visit on May 10 th, 2012 a noticeable recovery in the understory plant and shrub community was taking place over the entire burn area. Only in highly localized and small ( acre) patched that met the soil burn severity criteria for high severity where no plant growth was observed. In places where plant cover was not obvious, intact litter and duff layers and fine root systems were intact, with typically only the top ½ of the litter/duff layer being consumed or charred. These conditions were observed regularly, Vegetation Type Density Model a Low Moderate High Chaparral Sparse C b U Medium C C U High C C U Forest Sparse C U Medium C C U High C C C Sagebrush Sparse C U Medium C C U High C C U Grass Sparse C Medium C U High C C Table 4; Expected Soil Burn Severity Classes based on vegetation and density; a Percent canopy cover for sparse, medium, and high density are approximately defined as: Sparse 20%; Medium 20 60%; and High 60%. b Key: C = Common; U = Unlikely (but can occur in some circumstances); Gray cells = not applicable/does not occur NRCS Colorado State Office 15 of 27 May 20, 2012

16 even in areas that had been characterized as high severity due to high overstory mortality of the trees and shrubs. VI. ASSESSMENT MODELS (a) Single Storm Event Erosion Estimates (ERMiT) Robichaud et al, 2007 The Erosion Risk Management Tool (ERMiT) uses Water Erosion Prediction Project (WEPP) technology as the runoff and erosion calculation engine. WEPP simulates both interrill and rill erosion processes and incorporates the processes of evapo-transpiration, infiltration, runoff, soil detachment, sediment transport, and sediment deposition to predict runoff and erosion at the hillslope scale (Flanagan and Livingston, 1995). The ERMiT interface uses multiple runs of WEPP over a range of input parameters to predict event sediment delivery in probabilistic terms on burned and recovering forest, range, and chaparral lands. ERMiT Risk and Hazard Analysis ERMiT was used to analyze three representative catchments in a zone of concern. These three catchments expressed total overstory tree mortality as a result of extreme fire behavior. Soil burn severity was considered predominately moderate with either low or high and combination thereof. For the purposes of the analysis, we named the catchments, North, Central, and South. They are all located on the same soil, Legault- Tolvar-Rock outcrop complex, 50 to 70 percent slopes. Which are characterized as a variable depth to bedrock (17-60 inches), are well to extremely well-drained, gravelly loamy sandy, to very gravelly loam sand. The weather used in this analysis was a custom climate called the Lower North Fork Fire modified and weighted prism data, for the location; , at an elevation of 7200 feet. This data elevated the South Catchment North Catchment Central Catchment Figure 8: Sub-catchment in zone of concern. WEPP subcatchment delineations overlaid on soil severity severity and soil map. NRCS Colorado State Office 16 of 27 May 20, 2012

17 annual precipitation of the default weather data from Cheesman weather station by 10% for most parameters. Table 5. Catchments were measure in a GIS and ground truthed to estimate severity, slope angle, and length. Each catchment then was described by the relative proportion of low, moderate, and high severity (table 6), to produce total storm event analysis and Rainfall Event Rankings and Characteristics from the Selected Storms Storm Rank based on runoff (return interval) Storm Runoff (in) Storm Precipitation (in) Storm Duration (h) 10-min Peak Rainfall Intensity (in h-1) 30-min Peak Rainfall Intensity (in h- 1) Storm Date May 24 year 86 5 (20-year) August 23 year (10-year) August 12 year (5-year) August 21 year (2-year) August 1 year (11/3-year) August 1 year 96 Table probability 5: ERMiT Custom of single Climate storm Rankings event sediment and Descriptions; yields. Storm Ranking, expected run-off, total event precipitation, storm duration, 10 minute and 30 minute peak rainfall intensities, and measured date Analysis results revealed that probability of an average rainfall event (50 th percentile) would produce an estimated tons (low high severity yields) of sediment per acre in the first year, tons per acre in the second year, and by the fourth and fifth years tons per acre in an average storm event (Table 5) In consideration of the highly improbable and extreme case of a single storm event (10 th percentile) sediment yield, results were sobering. Model results indicate that an estimated tons per acre in the first year resulting from a single (10% probability) 2.9 inch precipitation storm (Table 5). These two scenarios, highly unlikely (10%) and likely (50%) in turn produced dramatically different catchment wide extrapolations. Combined catchments with respective burn severity proportions and the per acre storm event yield, produced tons and tons of sediment. NRCS Colorado State Office 17 of 27 May 20, 2012

18 North catchment, west and nw aspect Estimated acreage: Estimated Severity (%) Estimated severity acres length: 1327 feet long low 0 0 top middle toe mod % 41% 15% high Central catchment, west aspect Estimated acreage: Estimated Severity (%) Estimated severity acres length: 1394 feet long low 0 0 top middle toe mod % 57% 57% high South catchment, west and southwest aspect Estimated acreage: Estimated Severity (%) Estimated severity acres length: 876 feet long low top middle toe mod % 70% 90% high Table 5: ERMiT catchment descriptions, acres of severity per catchment, slope angles for the top and bottom 10% and middle 80%, and slope length. NRCS Colorado State Office 18 of 27 May 20, 2012

19 ERMiT Analysis per acre analysis by catchment Severity run Treatment Low Untreated N/A Mulch 1 ton/ac Year 1 Probabilities Year 2 Probabilities Year 3 Probabilities Year 4 Probabilities Year 5 Probabilities Year 10% Year Year 50% Year 10% Year 20% Year 50% Year 10% Year 20% Year 50% Year 10% Year 20% Year 50% Year 5 Year 20% Moderate Untreated Mulch 1 ton/ac High Untreated Mulch 1 ton/ac Year 50% Low Untreated N/A Mulch 1 ton/ac Moderate Untreated Mulch 1 ton/ac High Untreated Mulch 1 ton/ac Low Untreated Mulch 1 ton/ac Moderate Untreated Mulch 1 ton/ac High Untreated Mulch 1 ton/ac Table 6: ERMiT Catchment Analysis. Probabilistic yield associated with storm event that is in the 10 th, 20 th, and 50 th percentile event. Yields are in tons per acre for each respective severity class. Each severity class is further described by either untreated or treated condition and corresponding yield. NRCS Colorado State Office 19 of 27 May 20, 2012

20 ERMiT Analysis Total Catchment Yields Year 1 Probabilities Year 2 Probabilities Year 3 Probabilities Year 4 Probabilities Year 5 Probabilities Severity run Treatment Year 10% Low Untreated N/A Mulch 1 ton/ac Year Year 50% Year 10% Year 20% Year 50% Year 10% Year 20% Year 50% Year 10% Year 20% Year 50% Year 10% Year 20% Moderate Untreated Mulch 1 ton/ac High Untreated Mulch 1 ton/ac Year 50% Low Untreated N/A Mulch 1 ton/ac Moderate Untreated Mulch 1 ton/ac High Untreated Mulch 1 ton/ac Low Untreated Mulch 1 ton/ac Moderate Untreated Mulch 1 ton/ac High Untreated Mulch 1 ton/ac Table 7: ERMiT Catchment Extrapolation. Probabilistic yield associated with storm event that is in the 10 th, 20 th, and 50 th percentile event. Yields are in tons per catchment for each respective severity class. Each severity class is further described by either untreated or treated condition and corresponding yield. NRCS Colorado State Office 20 of 27 May 20, 2012