Location of Jamaica in the Caribbean; the Blue Mountains and Buff Bay in Jamaica; the Buff Bay River, other rivers and towns in west Portland.

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... Buff Bay watershed is located in the parish of Portland in the northeastern part of Jamaica (Fig. 1). The southern boundary of the watershed is the Grand Ridge of the Blue Mountains, the northern boundary is the north coast and the distance between the two measures 18 ...

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... many house- holds, the production of coffee or other horticultural produce for sale was very small and the activities of the household were supported by remittances from Jamaicans over- seas. Thirty-seven per cent of returnees bought the land entirely for agricultural pur- poses, hence reversing the migrant trend of leaving the land (Thomas-Hope, 1993). ...

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... of these slopes was rapid if left untended, except for steeper slopes (over 40°) and the scar and steeper reaches of landslide areas. The image of vegetative cover ranking is shown in Figure 10. ...

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... relative erosion classes determined from the literature (Table 39) were used in the model. The air photos did not reveal the understorey, an important factor under high canopy (Collier & Collins, 1980). The LUT data were coded on the basis of this relative ranking (Fig. 11). Without a considerable fi eldwork element, the problems as- sociated with medium scale air photos were impossible to resolve and secondary rather than air photo sources had to suffi ce in this model (Table ...

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... Erosivity -The very few high and extreme scores (Table 57) that resulted from overlaying agroclimatic zones and aspect were found within the Very Wet 3 zone in the extreme east of the research area (Fig. 12). Two contiguous areas were obvious on the image. The fi rst was a southwest facing valley head (13/818624) where a stream rises that drains towards Cedar Valley, but turns just north of west, joining the Buff Bay Riv- er at Wakefi eld. The second area (13/824615) was just south of the fi rst, a south-facing valley side, at the top of ...

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... clay loam, which was also a thin soil. Coffee was also grown on the Cuffy Gully and Valda grav- elly sandy loams, and this still gave a very high susceptibility to erodibility. The main areas of high erodibility were in the eastern and southern watershed, with a lobe of erodibility up into the Shentamee River valley, where coffee is grown (Fig. 13). Energy -The addition of the slope factor to agroclimatic zones and aspect in- creased the potential entrainment in terms of the energy and availability of runoff (Ta- ble 59). There are very few areas centred around the high scoring areas described in E1 that score the maximum in all three factors. A new area of disconnected patches ...

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... in terms of the energy and availability of runoff (Ta- ble 59). There are very few areas centred around the high scoring areas described in E1 that score the maximum in all three factors. A new area of disconnected patches also shows high scores around southern-fac- ing slopes of the Shentamee River, Mount Holstein and the village of Birnamwood (Fig. 14). A very large part of the research area (75 %) has moderate and high scores, reiterating the predominance of high angle slopes ...

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... data and the difference in results when better data (as used in the PED model) are available. This ranking differed from the PED model in placing the Cuffy Gully series highest on the erodibility scale instead of Hall's Delight. This altered the pattern of erodibility in the watershed, with the most susceptible soils west of the Buff Bay River (Fig. ...

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... but did not accurately refl ect the values estimated from the nomograph. The results suggested that the soils were not particularly erodible, but the relative nature of the model showed a pattern of erodibil- ity in which the most susceptible soils were to the west of the Buff Bay River, and on the southern and western watershed boundaries (Fig. 18). The third alternative scenario highlighted the soil protection offered by vegetative cover when the canopy produces a signifi cant litter, not a situation that occurs in the Buff Bay watershed. The PED coding presumed that a closed canopy would reduce sunlight and hence understorey. Plantations are of Pinus caribaea, an evergreen. ...

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... layer generated by a closed decid- uous canopy that gave some soil protection (Richardson, 1982;McDonald et al., 1996;Thomas, 1994). The ranks of the closed canopy categories were reduced by one (Table 67). This resulted in an image in which the previously high scoring western and south- ern watershed areas became less signifi cant for erosion (Fig. 19). The area of the re- search area in each of the relative erosion classes, for both the PED and the alternative scenarios, is given in Table ...

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... this lies partly with the proportion of land that was coded with the most erodible soil. In the original model, the Hall's Delight soil was most erodible and accounted for 40 % of the research area. The CIDA based soil ranking gave Cuffy Gully soils the highest score, accounting for 15 % of the research area, whilst the USLE ranking placed the Fig. 18. Alternative soil scoring system using USLE parameters (after Loch & Pocknee, ...

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... extreme potential erosion classes. The reduction of one rank class for high closed canopies affected the western and southernmost parts of the watershed, and individual valleys in the eastern part. As a more detailed analysis of the extreme po- tential erosion patches shows, it was the eastern part that was most generally suscep- tible to erosion (Fig. ...

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... USLE soils analysis not only signifi cantly reduced most of the patches in extent, it led to the complete disappearance of the Cedar Valley patch (Fig. 21). A patch was again created at Green Hill, a little larger than under the CIDA analysis, but the extreme erosion class was reduced to just over 11 ...