Area-Specific Recreation Use Estimation Using the National Visitor Use Monitoring Program Data

Transcription

1 United States Department of Agriculture Forest Service Pacific Nortwest Researc Station Researc Note PNW-RN-557 July 2007 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data Eric M. Wite, Stanley J. Zarnoc, and Donald B.K. Englis Abstract Estimates of national forest recreation use are available at te national, regional, and forest levels via te USDA Forest Service National Visitor Use Monitoring (NVUM) program. In some resource planning and management applications, analysts desire recreation use estimates for subforest areas witin an individual national forest or for subforest areas tat combine portions of several national forests. In tis researc note we ave detailed two approaces wereby te NVUM sampling data may be used to estimate recreation use for a subforest area witin a single national forest or for a subforest area combining portions of more tan one national forest. Te approaces differ in teir data requirements, complexity, and assumptions. In te new forest approac, recreation use is estimated by using NVUM data obtained only from NVUM interview sites witin te area of interest. In te all-forest information approac, recreation use is estimated by using sample data gatered on all portions of te national forest(s) tat contain te area of interest. Keywords: Recreation visits, National Visitor Use Monitoring program, recreation use estimation, recreation area. Introduction Recreation use estimates from te National Visitor Use Monitoring (NVUM) program, wic are developed at te national, regional, and forest levels, are useful for many administrative and management analyses. owever, for some situations, analysts desire recreation use estimates for areas below te level of a national forest Eric M. Wite is a researc economist, Pacific Nortwest Researc Station, Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 9733; Stanley J. Zarnoc is a matematical statistician, Soutern Researc Station, Forest Inventory, Monitoring, and Analysis, 200 Weaver Blvd., Aseville, NC 28804; and Donald B.K. Englis is visitor use monitoring program manager, 400 Independence Ave. SW, Wasington, DC

2 Researc note pnw-rn-557 We intend for te approaces to be applied in estimating recreation use for geograpically large areas. or for areas tat encompass subforest portions of more tan one national forest. In tis researc note, we describe two approaces tat can be used to develop tese area-specific NVUM recreation use estimates. We intend for te approaces to be applied in estimating recreation use for geograpically large areas. Te approaces are not appropriate for estimating recreation use at individual recreation sites, a collection of a few recreation sites, or small portions of te undeveloped areas of te national forest. Some appropriate applications include () estimating te national forest recreation use for a large watersed tat is of particular management interest, (2) estimating recreation use for a large separate unit of a national forest (e.g., te western unit of te iawata National Forest), or (3) developing an estimate of recreation use for a national forest tat is part of a multiple-forest administrative unit (e.g., an estimate for te uron National Forest portion of te uron-manistee National Forest). For example, te approaces described in tis paper ave been considered for use in estimating national forest recreation visitation witin te Cattooga River Watersed, wic is located along te borders of Sout Carolina, Georgia, and Nort Carolina and encompasses portions of tree national forests. Before undertaking area-specific estimation, we urge analysts to familiarize temselves wit te NVUM sampling program and to discuss teir analysis wit NVUM national-level staff. National Visitor Use Monitoring Program Te foundations of te NVUM program were initiated in 996 as a pilot project (Zarnoc et al. 2002) and officially implemented across te entire National Forest System (NFS) starting in calendar year 2000 (Englis et al. 2002). During NVUM round (lasting from January 2000 troug September 2003), eac national forest in te NFS underwent NVUM sampling for year. We include a brief description of te NVUM program and sampling approac; wile a more detailed description is available in Englis et al. (2002). Under NVUM, recreation use is quantified in terms of site visits and national forest visits. A site visit is defined as one person entering and exiting a recreation site or area on a national forest for te purpose of recreation and a national forest visit is defined as one person entering and exiting a national forest for te purpose of recreation (Englis et al. 2002). In te course of a single national forest visit, an individual may complete multiple site visits (e.g., an individual recreating at two day-use sites during a single national forest visit or an individual recreating in te undeveloped portion of a forest and at a campground during a single national forest visit). Based on NVUM round, te NFS ad 246 million site visits and 205 million national forest visits annually (USDA Forest Service 2004).

3 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data NVUM Sampling Approac Te NVUM sampling approac estimates recreation use by combining traffic counts wit information gatered via surveys of national forest visitors. Traffic counts are completed for a 24-our period and visitor questionnaires are administered at selected interview locations on selected days (termed sample days) witin individual national forests. Sample days witin a given national forest are selected via a stratified random sample from te population of all possible interview locations and days (termed site days) identified for tat national forest. Site days (and teir subset sample days) are stratified by te type of recreation area (termed te site type) and by te expected level of last-exiting recreation use (termed te use level). Four site types are recognized in te NVUM sampling protocol: day use developed sites (DUDS), overnigt use developed sites (OUDS), general forest area (GFA), and designated wilderness (wilderness). 2 A detailed definition of te four site types can be found in Englis et al. (2002). In te first round of NVUM, eac site day was classified into one of four use levels (ig, medium, low, and closed) based on te expected level of last exiting recreation traffic. Beginning in NVUM round 2, a fift use level, very ig, was added. Te levels of last-exiting recreation traffic tat distinguis one use level from anoter witin specific site types are identified by personnel on te respective national forest. Te combination of site type and use level (e.g., DUDS-medium) form te strata for te nonproxy NVUM sample. Visitation to some recreation sites and areas (e.g., campgrounds, wilderness areas, etc.) requires users to pay a fee, obtain a permit, or bot to recreate at te individual site or in te specific area. For some of tese sites and areas, te amount of traffic can be determined via fee or permit data, and an NVUM traffic count is not required. Under NVUM, tese sites are termed proxy sites. Te proxy count is combined wit data from te visitor questionnaires to estimate te recreation use at te proxy sites. Proxy sites are classified based on site type (i.e., DUDS, OUDS, GFA, or wilderness) and te type of proxy employed (e.g., a fee envelope, a permit, etc.). Tese sites are not classified by te level of last-exiting recreation use. Under te NVUM protocols and in te approaces described in tis researc note, proxy sites are treated separately from nonproxy sites wen estimating recreation use. Te NVUM proxy sites are identified in te prework analysis completed by national forest personnel. 2 An additional site type recognized under NVUM is viewing corridor. Use of tis type of site or area is not treated as national forest recreation use and tis site type is not considered ere.

4 Researc note pnw-rn-557 Estimates of recreation use in te various nonproxy and proxy strata (e.g., DUDS-medium, OUDS-fee envelope, etc.) are constructed from te NVUM sampling on a given national forest witin te respective strata. Te NVUM recreation use estimate for tat national forest is ten developed by summing te estimates of use (site visits and national forest visits) for all te nonproxy and proxy strata of te forest. Regional and national estimates are computed, in turn, by aggregating te visitation estimates of forests witin a region and all forests in te Nation, respectively. Estimating Area-Specific Recreation Use Te new forest approac is feasible only wit an appropriate number of sample days and visitor interviews witin eac stratum in te area of interest (AOI). We label te two approaces to estimating area-specific recreation use as te new forest approac and te all-forest information approac. In te former approac, recreation use is estimated for te area of interest (AOI) by using NVUM sample days and NVUM visitor surveys completed only at NVUM interview locations witin te AOI. In te latter approac, recreation use for te AOI is estimated based on information obtained from sample days and visitor interviews completed on all portions of te forest(s) containing te AOI. Te new forest approac is feasible only wit an appropriate number of sample days and visitor interviews witin eac stratum (i.e., DUDS-ig, GFA-low, etc.) in te AOI. Tis restriction may preclude te use of tis approac in many situations. Application of te new forest approac requires access to te prework data, te daily summary data, te proxy data, and te last-exiting recreation visitor survey data for te forest(s) involved (see Glossary for furter information on tese data). Te all-forest information approac does not require tat a minimum number of sample days or last-exiting recreation visitor surveys were completed witin te AOI because data from all observations on te forest(s) are incorporated in estimating AOI recreation use. owever, adoption of tis approac requires te assumption tat te patterns of recreation use witin te AOI are similar to recreation use patterns on te entire national forest(s). To complete te all-forest information procedures, an analyst must ave access to te prework data, te forest strata sampling results, te proxy data, and te last-exiting recreation visitor survey data for te forest(s) involved (see Glossary for definitions of tese data). Muc of te information required to complete eiter approac is available in te Natural Resource Information System uman Dimensions-NVUM (NRIS D-NVUM) application. Te NRIS D-NVUM application is available for download by USDA Forest Service personnel from te NRIS intranet Web site. Te NRIS D-NVUM application contains some information from te prework data, te daily summary data, te forest strata sampling results, and te proxy

5 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data data. Particularly useful tables and records include table 3 Summary Results by Sampling Stratum, table 32 Proxy Summary Results, table 33 Results From Eac Completed Nonproxy Survey Day, and te interview site records. We recommend tat analysts obtain te most recent version of tis application wen completing area-specific recreation use estimation. Initial Steps in Area-Specific Recreation Use Estimation Tree initial steps are required regardless of wic estimation approac is adopted: () identification and mapping of te AOI, (2) identification of AOI NVUM interview locations, and (3) determination of te population of site days witin site type/use level strata for nonproxy sites and site type/proxy type strata for proxy sites witin te AOI. Step is completed by using applicable forest maps and/or spatial databases, and steps 2 and 3 are completed by using te prework tat was completed by personnel on te national forest(s) prior to NVUM sampling. Identify and map te area of interest Te AOI sould be delineated based on te management activity, planning issue, or te researc question being addressed. Te adopted spatial boundaries sould be mapped eiter on paper map(s) or via a geograpic information system (GIS). Identify AOI NVUM interview locations In te NVUM prework, forest personnel ave identified locations trougout te national forest for visitor interviews and traffic counts. From te NVUM interview locations included in te prework, tose tat can be used to measure recreation use witin te AOI sould be identified. Tese AOI NVUM interview locations will be used bot in estimating te population of site days for te AOI and in identifying te NVUM sample days tat can be used to estimate area-specific recreation use via te new forest approac. In selecting te AOI interview sites, te goal is to identify NVUM interview locations tat capture visitors wo ave recreated in te AOI and do not capture (or capture very few) recreation users wo ave not recreated witin te AOI (fig. ). In cases were an interview site captures bot a large number of AOI and non-aoi visitors, analysts must use judgment in deciding weter to include te site as an AOI interview location. All DUDS and OUDS interview locations tat fall witin te boundaries of te AOI sould be identified as AOI interview locations. All GFA and wilderness interview locations witin te AOI sould also be included as long as tey exclusively (or nearly exclusively) measure AOI recreation use. Te NVUM interview locations located near but outside te AOI boundary sould be examined to determine if tey primarily capture recreation users exiting from te AOI and sould tus be 5

6 Researc note pnw-rn-557 Figure Area of interest (AOI) and non-aoi National Visitor Use Monitoring (NVUM) interview locations for an example AOI. DUDS day use developed sites, GFA general forest area, OUDS overnigt use developed sites, wilderness designated wilderness. included as AOI interview locations. For example, a GFA site located outside te AOI boundary but on a road used exclusively (or nearly exclusively) by recreation users from te AOI sould likely be included as an AOI interview location (see GFA sites located outside te AOI boundary in fig. ). Similarly, a wilderness interview location outside te AOI tat primarily captures recreation users leaving a wilderness area located witin te AOI sould likely also be included as an AOI interview location. In standard NVUM forest-level applications, interview sites are identified by individual forests to measure recreation use on te forest being sampled. In some cases, an interview location establised for one forest s NVUM sampling may also

7 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data ave been establised for NVUM sampling by an adjacent national forest, and bot forests may measure te same recreation use at tis location (regardless of weter or not te forests were sampled in te same year). Wen estimating AOI recreation use in multiple forest applications, interview sites tat ave been establised by more tan one forest and tat measure te same recreation use will lead to a double counting of recreation visits if no corrective action is taken (see examples in te next paragrap). To avoid double counting, tese duplicate interview locations must be identified and te number of site days adjusted, as described in te next step. 3 Several examples may elp to clarify wat situations may result in duplicate interview locations and te double counting of recreation visits. Te most clear duplicate interview location situation (and likely te rarest) is one in wic two or more forests ave identified te same OUDS or DUDS site as an interview location and measure te same recreation use at tat site. For example, if a DUDS picnic ground was located in te AOI on te border of two forests and bot forests identified tis as an interview location, tese interview locations would clearly represent duplicates and sould be identified. In some cases, te same DUDS or OUDS AOI interview site may ave been identified by multiple forests but may in fact measure different recreation use and would not represent duplicates. For example, a DUDS site identified by two forests may ave two traileads, eac serving trails on te respective forests. In tis case, te interview location does not measure te same recreation use (recreation use on te trail on forest B would not be counted in te recreation use estimate of forest A) and te establised NVUM interview locations are not duplicates. Less straigtforward is te identification of duplicate GFA and wilderness interview locations. Te key to correct identification is determining if te GFA and wilderness interview locations establised by te forests measure te same recreation use. For example, two interview locations establised at a single GFA parking lot located on te border of two forests would represent duplicates if te parking lot is used by canoeists and kayakers taking-out after recreating on a river tat forms te boundary of te forests. Ultimately, many situations will likely be unique, and te analyst will ave to use judgment in consultation wit nationallevel NVUM personnel to determine if duplicate interview locations are present. 3 In some instances, a particular recreation site may be identified as two NVUM interview locations, bot aving different site types. For example, bot an OUDS interview location and a DUDS interview location may ave been identified witin a developed campground tat also provides day use lake access. Similarly, a DUDS location and a wilderness location may be identified witin a single day use site wit picnic grounds and a trailead into a wilderness area. Tese are valid NVUM interview locations and sould not be considered duplicates. 7

8 Researc note pnw-rn-557 Wen more tan one national forest is involved, it is advantageous to identify te number of site days witin strata separately for eac forest involved. Determining te population of site days Using te calendar tat was constructed for eac AOI interview location in te NVUM prework, determine te number of site days identified witin eac stratum (e.g., DUDS-medium, OUDS-fee envelope, etc.), keeping proxy and nonproxy sites separate, for te AOI NVUM interview locations (table ). Operationally, tis involves determining te number of site days identified in te NVUM prework for eac AOI NVUM interview location, ten summing across AOI interview locations witin strata. Wen more tan one national forest is involved, it is advantageous to identify te number of site days witin strata separately for eac forest involved (table 2). Table Determining te NVUM site day population for an example area of interest Site type a Use level Site days Nonproxy locations: DUDS ig 75 Medium 334 Low,95 Closed 2 OUDS ig Medium 37 Low 207 Closed 20 GFA ig,063 Medium 3,35 Low 6,382 Closed 7,454 Wilderness ig 70 Medium 300 Low 888 Closed,297 Proxy locations: DUDS Fee envelope (open) 7 Fee envelope (closed) 294 OUDS Fee envelope (open) 43 Fee envelope (closed) 587 GFA Fee envelope (open) 275 Fee envelope (closed) 90 Total 24,455 Total (excluding closed site days) 4,492 a DUDS day use developed sites, OUDS overnigt use developed sites, GFA general forest area, and wilderness designated wilderness.

9 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data Wen duplicate NVUM interview locations ave been identified for te same pysical location, site days at te duplicates tat correspond to measurement of te same recreation use sould be counted only once. Generally, analysts will simply include te site days at te interview location establised by one of te forests and discard te site days establised by te oter forests. In some cases, te open season (te nonclosed site days) establised by one forest may be longer tan tat establised by te oter forests. In tese cases, it is likely best to use te longer open season site days and exclude te site days establised by te oter forests to ensure tat recreation use is estimated based on te longest season. Table 2 Determining te NVUM site day population for an example area of interest involving multiple forests Site type a Use level Forest A Forest B Forest C All tree Nonproxy locations: DUDS ig Medium Low 45,060 90,95 Closed OUDS ig 0 0 Medium Low Closed GFA ig ,063 Medium,23 883,345 3,35 Low 599 3,78 2,065 6,382 Closed 3,588 3, ,454 Wilderness ig Medium Low Closed ,297 Proxy locations: DUDS Fee envelope (open) Fee envelope (closed) OUDS Fee envelope (open) Fee envelope (closed) GFA Fee envelope (open) Fee envelope (closed) Totals 8,395,35 4,745 24,455 Totals (excluding closed site days) 3,464 7,039 3,989 4,492 a DUDS day use developed sites, OUDS overnigt use developed sites, GFA general forest area, and wilderness designated wilderness.

10 Researc note pnw-rn-557 In rare cases, te establised site days on forest A and forest B may measure duplicate recreation use for part of te year and unique recreation use during anoter part of te year (e.g., an interview location at a trailead for a single trail tat is open on forest A all year but closes on forest B during part of te year owing to snow conditions). In tese cases, te site days tat measure duplicate recreation use sould be counted only once. Te site days tat measure unique recreation use at tis duplicate location sould ten be added to te duplicate site day total. Again, many duplicate interview location situations will be unique, and te analyst sould use judgment and consult national-level NVUM personnel. Estimating Area-Specific Recreation Use Via te New Forest Approac Determining te Adequacy of te NVUM Sample Under te new forest approac, NVUM sample days and visitor interviews witin te AOI are used to develop estimates of te number of site visits witin te AOI and te number of AOI visits (AOI visits are analogous to national forest visits). To develop reliable estimates of AOI recreation use, tere must be bot a reasonable number of sample days and a reasonable number of visitor interviews witin eac stratum in te AOI. Based on te NVUM sampling protocol, we recommend a minimum of 8 sample days for eac nonproxy stratum and a minimum of 4 sample days for eac proxy stratum (Englis et al. 2002). Wen te population of site days in a stratum is less tan 8 or oterwise small, it is more important to ensure tat te number of sample days is reasonable and te sampling fraction (site days to sample days) is adequate rater tan being constrained solely by te 8-sample-day minimum. For example, if tere are only 7 site days in a given stratum, ten 4 sample days may be appropriate. Similarly, if just 6 site days exist witin a stratum, ten 7 sample days may be reasonable. aving a reasonable number of visitor interviews witin eac stratum is likely more restrictive tan meeting te NVUM minimum number of sample days. At nonproxy sites, data gatered via visitor interviews are used to estimate () te percentage of visitors wo are last-exiting recreationists, (2) te average party size of last-exiting recreation parties, and (3) te number of sites visited per national forest visit. At proxy sites, data from last-exiting recreation visitors are used to calibrate te proxy in order to estimate recreation use. Because te NVUM protocols do not identify te minimum number of recreation visitor interviews witin eac stratum, analysts must determine wat is reasonable for teir specific application. 0

11 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data aving a less tan adequate number of sample days and/or a limited number of visitor interviews in one or more nonproxy strata does not immediately preclude using te new forest approac. owever, if several nonproxy strata ave a small number of sample days, or a very limited number of visitor interviews, te new forest approac is likely not appropriate or may need to be modified (see te later section entitled Options for Meeting Minimum Sample Size Requirements ). Individual analysts will ave to use judgment as to weter te number of sample days and visitor interviews are reasonable given te specific situation. Altoug it is preferable to ave at least 4 sample days and a reasonable number of visitor interviews in every proxy stratum, it is not entirely necessary (and probably not likely). At proxy sites, te proxy provides a known count of te traffic at te site and only a conversion factor (obtained from surveys of last-exiting recreation visitors) is needed to convert tis proxy count to an estimate of recreation use. If necessary, te proxy count can be converted to a recreation use estimate based on data from visitor interviews completed at interview locations witin te same proxy stratum but outside te AOI. Te proxy counts temselves are still obtained for te individual proxy sites witin te AOI. Analyst judgment and local knowledge are necessary to determine weter te proxy conversion factor obtained from te larger geograpic area is appropriate to te proxy sites in te AOI. If necessary, te proxy count can be converted to a recreation use estimate based on data from visitor interviews completed at interview locations witin te same proxy stratum but outside te AOI. General Discussion of Recreation Visit Calculations Te formulas in te following sections are adapted from Englis et al In te new forest approac, only data gatered from sample day observations at te AOI interview locations are used in estimating recreation use. Te use of AOI-specific data is designated in te formulas below by te symbol. Estimation of visits (bot site visits and visits to te AOI in general) is acieved troug () developing estimates of visits in te nonproxy strata, (2) developing estimates of visits in te proxy strata, and (3) combining nonproxy and proxy visit estimates into a single total visit estimate. Calculations for site visit estimation are detailed first, followed by te calculations for AOI visit estimation. Calculating Site Visits Witin te AOI for Nonproxy Strata Te first step in estimating te number of site visits in te nonproxy strata is to estimate te mean number of site visits for given nonproxy stratum witin te AOI ( SV ):,

12 Researc note pnw-rn-557 SV C P V, were C is te mean number of cars counted on te NVUM traffic counter adjusted for te number of axles and two-way traffic in stratum as estimated from te daily summary data, P is te proportion of exiting traffic tat is last-exiting recreationists averaged across all sample days in stratum (also estimated from te daily summary data), V is te number of persons in lastexiting recreation parties averaged across all sample days in stratum witin te AOI as estimated from te last-exiting recreation visitor survey data, and designates tat tis information is drawn from te AOI interview locations. Te total number of site visits in nonproxy stratum is computed as were SV N SV, [] N is te known population of site days in stratum witin te AOI. An estimate of te total number of site visits to nonproxy sites witin te AOI is calculated as TOTALSV NP N C P V, were is te total number of nonproxy strata witin te AOI. Te total site visit equation comes from a summation over te strata of equation. Assuming independence of C, P, and V, te variance of te total nonproxy estimate is C P ( P ) ( ) + ( ) ( ) + V V C CV V P ( C P ) V ( V ) V ( TOTALSV NP ) N 2, V were V ( ), V ( ), and V ( ) are variances calculated in te usual manner. Calculating Site Visits Witin te AOI for Proxy Strata Site visit estimates for te proxy strata witin te AOI are developed from te following: () te annual total proxy count for a given site k witin a given proxy stratum (AP k ) as identified in te proxy data, (2) te percentage of visitors complying wit te proxy requirement (e.g., percentage obtaining a wilderness permit, etc.) for a given site k witin a given proxy stratum (CR k ) as reported in te proxy data, and (3) a conversion factor estimated by using te last-exiting recreationists visitor survey data ( A ). 2

13 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data Te first two components (AP k and CR k ) are combined to develop te compliance-based proxy count for eac proxy site (PC k ): AP k PC k. CRk In many instances, PC k will be directly available as part of te proxy data contained witin te NRIS D-NVUM application. Using PC k, te average daily proxy count ( PC ) for a given proxy stratum is calculated as follows: PC K k K k PC N k k, [2] were N k is te known number of proxy site days for site k in stratum, and K is te total number of proxy sites in stratum witin te AOI. PC is a known constant and, tus, as no variance. Tis fact is used advantageously later in te variance equation for te total proxy estimate. Te conversion factor A is constructed incorporating te sum of group size for all groups surveyed in stratum of te AOI on given sample day i ( SG i ) and te sum of te number of proxies completed by all groups surveyed in stratum of te AOI on sample day i ( SR ) (bot estimated from te last-exiting visitor survey i data by using responses to te proxy-specific questions) via te following formula: A n i n i SG SR i i, were n is te number of sample days in stratum witin te AOI. Te average number of site visits across all sample days in proxy stratum ( SV ) is ten calculated as SV A PC. [3] Te total number of site visits in proxy stratum can be computed by expanding in a similar manner as was done in equation. 3

14 Researc note pnw-rn-557 An estimator for te total number of site visits to all proxy sites witin te AOI is p TOTALSV N A PC, were all variables are as defined previously. Te variance of tis estimator is ten V ( TOTALSV ) N PC V ( A ), P 2 2 were te variance of A is based on te ratio of means and is computed as V ( A ) n n n 2 SGi + A 2 2 SRi 2A( SGiSRi ) n 2 SR i i i i n ( n ) i n. Calculating te Total Number of Site Visits Witin te AOI Te total number of site visits witin te AOI, combining proxy and nonproxy sites, is TOTALSV TOTALSV NP + TOTALSV P wit variance calculated as V ( TOTALSV ) V ( TOTALSVNP ) + V ( TOTALSV P )., Because some visitors will recreate at multiple locations witin te AOI, te number of site visits in te AOI will generally be greater tan te number of AOI visits. Area of Interest Visits In most applications, te AOI will likely contain a number of recreation sites and areas (i.e., DUDS, OUDS, GFA, and wilderness). Because typically some visitors will recreate at multiple locations witin te AOI, te number of site visits in te AOI will generally be greater tan te number of AOI visits. Te AOI visits are calculated by using, in part, te number of sites visited and weter or not recreation occurred in te GFA or in wilderness areas as reported by individual NVUM survey respondents in te last-exiting recreationist survey data. Respondents to te NVUM visitor survey identified te number of sites visited, te number of days spent in te GFA, and te number of days spent in wilderness areas on teir current trip to te entire national forest. In some cases, te sites visited, te GFA recreation, or wilderness recreation tat were reported by individual respondents may ave occurred outside te AOI. Lacking oter information, it is assumed tat 4

15 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data te reported site visits and GFA and wilderness recreation all occurred witin te AOI. If violated, tis assumption could yield an underestimation of AOI visits. Te number of AOI visits would be underestimated because te number of sites visited is used to adjust te site visit estimate downward. In rare instances, wen te AOI contains only GFA or only wilderness areas, te number of AOI visits will equal te number of site visits. Calculating AOI Visits for Nonproxy Strata Te first step in estimating AOI visits for nonproxy strata is to estimate te number of AOI visits on sample day i in stratum ( AOIV ). Tis is computed as follows: i i i AOIV C P CBAR, were C i te number of cars obtained on te NVUM traffic counter adjusted for te number of axles and two-way traffic on sample day i in stratum witin te AOI as reported in te daily summary data and P is as defined previously. CBAR is computed as i i CBAR i ni n i j V ij NS ij, were n i is te number of last exiting veicles in stratum on sample day i, V ij is te number of visitors in veicle j in stratum on sample day i, and NS is te number of sites visited by individuals in veicle j in stratum on sample day i, all witin te AOI. Recreation tat was reported to ave occurred in te GFA or in wilderness areas during te visit (i.e., days in te GFA > 0, days in wilderness > 0) is counted as one site visit for tat site type regardless of te number of days in te GFA or days in wilderness. For example, if a respondent reported visiting 2 DUDS, spending 2 days in te GFA, and spending 3 days in a wilderness area during te national forest visit, NS ij equals 4 (2 for DUDS visited + for GFA recreation + for wilderness recreation). Te average number of AOI visits across all sample days witin nonproxy stratum is computed as AOIV n i AOIV n i. ij 5

16 Researc note pnw-rn-557 were Te number of AOI visits in nonproxy stratum is ten computed as AOIV N AOIV, [4] N is te known number of site days in stratum of te AOI. An estimate of te total number of AOI visits associated wit te nonproxy sites in te AOI is calculated as wit variance TOTALAOI NP NP N N N 2 AOIV V ( TOTALAOI ) N V ( AOIV ), were V ( AOIV ) is calculated in te usual manner. Calculating AOI Visits for Proxy Strata Te AOI visits for proxy strata are estimated following te same general approac as used in estimating site visits for te proxy strata. owever, an adjustment factor ( AF ) is used to account for te number of sites visited per AOI visit. Te conversion factor AF is developed as were were AF SR i is as defined previously and ij n i n i SC SR i i SC i is computed as J i Vij SC i ( ), NS j V is te number of visitors in stratum on sample day i in party j, ij,, NS ij is te number of sites visited by party j in stratum on sample day i, and J i is te total number of parties in stratum on sample day i, all witin te AOI. Reported recreation in te GFA or wilderness area during te visit (i.e., days in te GFA > 0, days in te wilderness > 0) is counted as one site visit for tat site type regardless of te number of days in te GFA or wilderness area. Te average number of AOI visits in proxy stratum ( AOIV ) is computed as AOIV AF PC, 6

17 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data were AF is as computed above and PC is te mean daily proxy count for proxy stratum as calculated by using equation 2. Te number of AOI visits in proxy stratum witin te AOI ( AOIV ) is ten computed by expansion as in equation 4. An estimate of te total number of AOI visits associated wit te proxy sites in te AOI is wit variance TOTALAOI, P N AF PC V ( TOTALAOI ) N PC V ( AF ). P 2 2 were V ( AF ) is calculated based on te ratio of means in a similar way as V ( A ) was as detailed in te previous section. Calculating te Total Number of AOI Visits Te total number of AOI visits is ten TOTALAOI TOTALAOI NP + TOTALAOI, wit variance V ( TOTALAOI ) V ( TOTALAOI NP ) + V ( TOTALAOI P ). P Options for Meeting Minimum Sample Size Requirements Several options are available to meet te minimum sample size necessary to complete te new forest estimation approac. In some cases, it may be possible to combine adjacent use levels witin a given site type (e.g., DUDS-medium and DUDS-low), allowing for pooling of sample day observations and last-exiting recreation visitor interviews witin te pooled stratum. Tis option may be particularly appropriate if two adjacent use levels (e.g., low and medium) witin a single site type ave small numbers of site days, sample days, or visitor interviews or if one use level witin a site type as few site days, sample days, or visitor interviews and anoter as many site days, sample days, or visitor interviews. Wen pooling across use levels, te analyst sould be cognizant of te potential for introducing bias into te visit estimates and for increasing te variance of te resulting recreation use estimate. A biased visit estimator may result if te numbers of sample days occurring witin te pooled use levels are not proportional to te population of site days witin te use levels. For example, a biased estimator could result in cases were Several options are available to meet te minimum sample size necessary to complete te new forest estimation approac. 7

18 Researc note pnw-rn-557 a similar number of site days exist in two use levels but vastly dissimilar number of sample days occurred in te two use levels. Additionally, if te visit beavior of recreationists (e.g., party size, number of sites visited, etc.) in te two use levels is different, ten te resulting estimate could be biased. As te second NVUM round is completed, tere may be opportunities to increase te number of sample days and/or te number of last-exiting visitor interviews witin AOI strata by pooling data across NVUM rounds. Significant canges witin te use level breakpoints or te classification of NVUM interview locations witin te involved forest(s) may preclude tis pooling. Pooling across NVUM rounds is not appropriate if tere ave been significant canges in te amount of recreation use on te forest between NVUM rounds. Cross-round pooling will also make it impossible to identify trends in recreation use levels between te sample years. Analysts sould consult national-level NVUM personnel to determine te feasibility of pooling across sampling rounds. Sample day observations and visitor interviews completed at NVUM interview locations near te boundary of te AOI could be combined wit sample day observations and visitor interviews witin te AOI (witin strata). Site days from tese nearby interview locations sould not be included in te total number of site days for te AOI (i.e., N ). Incorporation of sample day data and interviews completed at nearby interview locations sould occur only if recreation use levels (witin strata) at te nearby interview locations are similar to recreation use levels witin te AOI. In some cases, te new forest approac may become feasible only if information from all portions of te forest can be used in estimating recreation use for specific strata (as done in te all-forest information approac presented next). Information from outside te AOI could include te average site visit ( SV ) or average national forest visit ( NFV ) estimates for a specific stratum as determined for te entire forest, te average number of sites visited per national forest visit in stratum ( NS ), or te average number of people per veicle in stratum ( V ). As more information from outside te AOI is used, te recreation use estimate becomes more dependent on te assumption tat recreation use patterns witin te AOI do not differ significantly from recreation use patterns outside te AOI, witin strata. Estimating Area-Specific Recreation Use Via te All-Forest Information Approac Te all-forest information approac involves less complex calculations and does not require te analyst to ave access to te daily summary data. Analysts must still ave access to te prework data, te forest strata sampling results, te proxy count 8

19 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data reports, and last-exiting recreationist survey data for all of te national forests involved. Te all-forest information approac assumes tat recreation use patterns witin te AOI do not differ, witin strata, from recreation use patterns on te forest(s) in general. Tis approac is likely inappropriate wen () te level of recreation use, witin strata, in te AOI is known to differ substantially from te level of use on te forest in general witin te same strata; or (2) te pattern of site visits per national forest visit differs markedly between te AOI and te forest in general. Te former restriction is not meant to preclude use of tis approac in an AOI tat as lower total levels of recreation use as result of a longer closed season or more low-use site days, as tis difference is accounted for in te use level stratification of site days. Calculating Site Visits Witin te AOI for Nonproxy Strata In te all-forest information approac, te average site visits per sample day for stratum ( SV ) is gatered from te forest strata sampling results reported for te entire national forest (table 3). 4 In multiple-forest applications, te appropriate SV are gatered separately for eac forest involved (table 4). 4 For comparison, in te new forest approac SV was calculated by using data gatered only from witin te AOI. Table 3 Example average number of site visits witin nonproxy strata applied to te area of interest Average number Site type a Use level of site visits DUDS ig 236. Medium 85.8 Low 47.6 OUDS ig 4.3 Medium 32.7 Low 0.7 GFA ig 87.7 Medium 54.9 Low. Wilderness ig 85.3 Medium 3.6 Low 3.6 a DUDS day use developed sites, OUDS overnigt use developed sites, GFA general forest area, and wilderness designated wilderness. Table 4 Example average number of site visits witin nonproxy strata for a multipleforest area of interest Site type a Use level Forest A Forest B DUDS ig b 53.7 Medium Low OUDS ig 4.3 Medium 32.7 Low 0.7 GFA ig 6.2 b Medium Low b Wilderness ig 85.3 b Medium 67.3 Low a DUDS day use developed sites, OUDS overnigt use developed sites, GFA general forest area, and wilderness designated wilderness. b No site days exist witin te area of interest on tis national forest. b b b 9

20 Researc note pnw-rn-557 In single forest applications, equation is used to compute te total number of site visits in nonproxy stratum ( SV ) of te AOI. Tis calculation uses te average site visit estimate for stratum ( SV ) (as estimated for te wole forest) and te known number of site days in stratum occurring in te AOI ( N ). An estimate of te total number of site visits for all nonproxy sites can be computed as wit variance TOTALSV NP N SV V ( TOTALSV ) N V ( SV ), NP were V ( SV ) is obtained from te forest strata sampling results and is te total number of nonproxy strata in te AOI. In multiple-forest applications, te total number of site visits for nonproxy AOI stratum ( SV ) is calculated as F f f 2 f, SV N SV, [5] were N f is te number of site days in stratum of forest f, SVf is te average site visit estimate per sample day in stratum estimated for all of forest f, and F is te total number of forests in te AOI. Te total number of site visits for nonproxy sites (in te multiple-forest application) is computed as wit variance TOTALSV N NP F f f f SV V ( TOTALSV ) N V ( SV ), NP F f 2 f, f were is te total number of strata witin te AOI, V ( SVf ) is obtained from te forest strata sampling results for forest f, and all oter variables are as defined previously. Calculating Site Visits Witin te AOI for Proxy Strata Site visit estimates for proxy sites witin te AOI are estimated by using () te compliance-based proxy count for eac proxy site k in stratum (PC k ), (2) te number of site days for proxy site k in stratum (N k ), and (3) te conversion factor 20

21 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data for proxy stratum ( A ) as estimated from proxy sites in stratum bot witin and outside te AOI and reported in te proxy data. PC k and A are available as part of te proxy data contained witin te NRIS D-NVUM application. Items and 2 are used to calculate te average daily proxy count ( PC ) for a given proxy stratum by using equation 2. Using te average daily proxy count PC and te proxy conversion factor A, te average site visit estimate for proxy stratum ( SV ) can ten be computed by employing equation 3. As wit nonproxy sites, in single-forest applications, te total number of site visits for proxy stratum ( SV ) is computed by multiplying te average site visits for proxy stratum ( SV ) by te number of site days in proxy stratum witin te AOI ( N ) (equation ). An estimator for te total number of site visits at proxy sites in te AOI is Te variance is TOTALSV P N A PC V ( TOTALSV ) N PC V ( A ), P 2 2. were V ( A ) is based on te ratio of means as described previously. In multiple-forest applications, te total number of site visits for proxy strata in te AOI ( SV ) is calculated by using equation 5 and te SVf values for te respective forests. 5 An estimate of te total number of site visits for te proxy sites in te multiple-forest AOI is ten calculated as were N, A, and f f TOTALSV P F f N f A f PC PC f are as defined previously and determined for te respective forest f. Te variance of te total site visit for proxy sites is ten calculated as F V ( TOTALSV ) N PC V ( A ), P f were all variable are as defined previously. f 2 2 f f, f 5 If proxy strata occur on only one forest in a multiple-forest application, te single-forest application calculations can be followed rater tan te multiple-forest calculations. 2

22 Researc note pnw-rn-557 Calculating te Total Number of Site Visits Witin te AOI Te total number of site visits witin te AOI is TOTALSV TOTALSV NP + TOTALSV P, wit variance calculated as V ( TOTALSV ) V ( TOTALSVNP ) + V ( TOTALSV P ). Calculating AOI Visits for Bot Nonproxy and Proxy Strata Te AOI visits for proxy and nonproxy strata are calculated by using te same formulas and are presented togeter. We present formulas for te multiple-forest application, as te single-forest application is simply a special case. First, te average number of national forest visits witin eac nonproxy and proxy stratum ( NFV ) is computed separately for eac forest f as f NFV f SVf, NS were SV f is te average number of site visits in stratum witin forest f. NS f is te average number of sites visited per national forest visit in stratum witin forest f and is computed as te aritmetic mean NS f J NS jf j, were NS jf is te number of sites visited as reported by individual j in stratum witin forest f. Reported recreation in te GFA or wilderness during te visit (i.e., days in te GFA > 0, days in wilderness > 0) is counted as one site visit for tat site type regardless of te number of days in te GFA or wilderness. J f is te number of individuals sampled witin stratum of forest f. Te total number of AOI visits for nonproxy strata ( NFV ) is computed as J f f F NFV N f f NFV f, were N f is te number of site days in stratum of forest f witin te AOI and F is te total number of forests witin te AOI. 22

23 Area-Specific Recreation Use Estimation Using te National Visitor Use Monitoring Program Data An estimate of te total number of AOI visits calculated for eiter proxy ( TOTALAOI ) or nonproxy strata ( TOTALAOI ) is P NP TOTALAOI F f N f NFV f wit variance V ( TOTALAOI ) N V ( NFV ), F f were V ( NFVf ) is te variance of NFV f and is calculated in te usual manner and all variables are as defined previously. Calculating te Total Number of Visits to te AOI An estimate of te total number of AOI visits for proxy and nonproxy strata combined is wit variance 2 f TOTALAOI TOTALAOI NP + f TOTALAOI V ( TOTALAOI ) V ( TOTALAOI ) + V ( TOTALAOI ). NP P P Multiple Forest AOI Visit Adjustment Te NVUM visitor survey respondents complete te questionnaire in regard to te current visit tey are completing to te national forest on wic tey were sampled. Wen completing te questionnaire, respondents report te number of sites visited and recreation in te GFA and wilderness tat occurred during te current national forest visit. Tis information is used to determine te number of site visits occurring per national forest visit. Respondents do not report visits to sites, GFA recreation use, or wilderness recreation use on adjacent national forests tat may ave occurred during te respondent s current recreation trip. Because te borders witin te AOI between te multiple forests now represent internal divisions tat are being assumed away, visits to te AOI tat include unreported site visits, GFA recreation use, or wilderness recreation use on land witin te AOI managed by anoter forest during te same trip will yield an inflated AOI visit estimate. To correct for tis, te final AOI visit estimate sould be divided by te mean number of forests visited during an AOI visit (tis mean sould be greater tan or equal to.0). Tese data are not available in te NVUM data, and tus local information and analyst judgment must be used to determine te appropriate value Wen completing te questionnaire, respondents report te number of sites visited and recreation in te GFA and wilderness tat occurred during te current national forest visit. 23

24 Researc note pnw-rn-557 for te adjustment. Note tat te potential overestimation of AOI visits owing to unreported site visits and GFA recreation on oter AOI forests may be offset by a potential underestimation of AOI visits resulting from te assumption tat all reported site visits and GFA recreation use occurred witin te AOI (wen it may ave in fact occurred outside te AOI). In some cases, it may be best to assume tat tese balance and no multiple-forest AOI visit adjustment be taken. If a site day adjustment for duplicate interview locations as already been taken, a multiple-forest AOI visit adjustment does not need to be adopted for tat portion of recreation use associated wit te duplicate interview locations, as it as already been accounted for by ensuring tat te site days are counted only once. Te remaining recreation use not associated wit te duplicate interview locations is still subject to te multiple-forest AOI visit adjustment. Summary Currently, NVUM-based recreation visitation estimates are reported at te national, regional, and forest levels. In tis researc note, we ave described two approaces for estimating recreation use witin large subforest areas by using NVUM data. Tese subforest areas may fall witin a single forest or witin multiple forests. Te two approaces differ in data requirements, complexity of estimation, and assumptions required. Te new forest approac requires access to more of te NVUM data and is more analytically complex tan te all-forest information approac. Altoug te all-forest information approac requires less data and is less complex, it requires te assumption tat recreation-use patterns witin te area of interest are similar to tose found on te forest in general, witin strata. Regardless of te approac adopted, analysts are strongly encouraged to coordinate teir area-specific recreation use estimation wit nationallevel NVUM personnel. 24