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首页> 外文期刊>Journal of hydrology, New Zealand >Gully degradation, stabilisation and effectiveness of reforestation in reducing gully-derived sediment, East Coast region, North Island, New Zealand
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Gully degradation, stabilisation and effectiveness of reforestation in reducing gully-derived sediment, East Coast region, North Island, New Zealand

机译：新西兰北岛东海岸地区的沟壑退化，稳定化和重新造林在减少沟壑源性沉积物方面的有效性

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Gully stabilisation was modelled by measuring the change in 'active' gully area before planting with exotic pines and at the end of a 40-year reforestation period. A degradation model based on DEMs of gullies at differing stages of development was used to calculate sediment production from reforested gullies in both Cretaceous and Tertiary geological terrains. The total volume of gully-derived sediment was calculated at catchment-scale by combining the gully degradation and stabilisation models with GIS-based mapped distributions of gullies in 1957 and 1997, and then expressed as an equivalent percentage of the average annual suspended sediment yield for each of the three largest and heaviest sediment-laden rivers within the East Coast region, North Island. The modelling of gully-derived sediment yields before and after a 40-year reforestation period (1957-1997) provided a measure of the effectiveness of past reforestation efforts in reducing gully-derived sediment yield. These models were then used to forecast potential reductions in gully-derived sediment for future reforestation scenarios. The probability of gullies stabilising (a measured reduction in 'active' gully area following planting with pines) was strongly associated with gully size and the number of years since planting. The probability of gullies of equivalent size stabilising in response to planting is similar in both the Cretaceous and Tertiary geological terrain. Past reforestation has reduced sediment yield by 33%, 17% and 20% in the Waipaoa, Waiapu and Uawa catchments, nonetheless during the measurement period forested gullies in both terrains collectively contributed 55%, 23% and 54% of the total gully-derived sediment yield in these respective catchments. At catchment scale, gully-derived sediment yield in each of the three major catchments could be halved by 2030 and remain constant thereafter if all remaining untreated gullies were reforested before 2020 and no new gullies were initiated during this period. The greatest number of untreated gullies occurs in the Waiapu catchment, where it is expected that sediment yield would decline by 11Mt/year by the end of the modelling period.
机译：通过在种植异国情调的松树之前和40年造林期结束时测量“活动”沟壑面积的变化来模拟沟壑稳定。基于白垩纪和第三纪地质地形中不同发育阶段的沟渠的DEM的退化模型用于计算造林沟渠的沉积物产量。通过将沟壑退化和稳定模型与基于GIS的沟壑分布图相结合，在流域尺度上计算出沟壑沉积物的总量，然后将其表示为当年平均悬浮泥沙产量的等效百分比。北岛东海岸地区内三条最大，最重的含沙河流中的每条河流。在40年的重新造林时期（1957-1997年）之前和之后，以沟壑为基础的沉积物产量模型为过去的造林活动在降低以沟壑为基础的沉积物产量方面的有效性提供了一种度量。然后将这些模型用于预测未来造林情况下沟源沉积物的潜在减少量。沟壑稳定的可能性（在种植松树后测得的“有效”沟壑面积的减少）与沟壑的大小和自种植以来的年限密切相关。在白垩纪和第三纪地质地形中，由于种植而引起的等尺寸沟壑稳定的可能性相似。过去的重新造林使怀波阿，怀阿普和Uawa流域的沉积物产量减少了33％，17％和20％，尽管如此，在测量期间，两个地区的森林沟壑共同贡献了源自沟壑的总面积的55％，23％和54％这些流域的沉积物产量。在流域规模上，如果所有剩余未经处理的沟壑在2020年之前重新造林并且在此期间未启动新的沟壑，则到2030年，三个主要流域每一个的沟谷沉积物产量可能减半，并保持不变。未经处理的沟壑数量最多的地区是怀阿布流域，预计到建模期末，沉积物产量将以每年11Mt的速度下降。

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