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William Denevan classifies terraces into check dams and cross-channel terraces, sloping field terraces, bench terraces, and broad field bench terraces. Check dams and cross-channel terraces are built across narrow valleys, drainages, and steams. Bench and sloping terraces are built on mountain slopes, but vary in that bench terraces have level retaining walls that give hillsides a stepped look, whereas sloping terrace walls run across and down the slope. Terracing agricultural system helps manage the ﬂow of water, slowing runoff and letting excess to moisture drain and allowing crops to be well watered. In desert environments with violent and episodic rain events, terraces decrease runoff and improve soil moisture retention. In other cases, terraces agriculture can help direct the ﬂow of water so that it is used more effectively, irrigating and even ﬂooding crops which require large amounts of water, as in the case of rice paddies. Terracing curtails degradation, soil erosion and ensures sediment depth for agricultural production. It can create microclimates that protect crops from high winds and frost, and can increase the amount of solar radiation on a ﬁeld.
The impact of terracing on the landscape and its vegetation can be felt long after terraces are abandoned, if they have not been lost to erosion. For example, the Maya site of Caracol, Belize, was abandoned around A.D. 900, but the terraced topography around the site affects the current vegetation and forest structure. The terraced areas usually have taller forests that are more vertically diverse, with more closed canopies. In the Colca Valley, Peru, abandoned terrace areas displayed thicker a soil horizons and greater levels of phosphorous, nitrogen, and organic carbon. By building terraces, farmers are able to seek higher elevation where rain conditions may be more favorable, or where different crops can be grown or even developed. The terracing agriculture ensures greater agricultural output, while at the same time making dramatic and visible statements of power, of investment in labor and resources, and of land ownership.