Design Features of Ancient Agricultural Terrace Walls in the Negev Desert: Human‐made Geodiversity

Abstract

Thousands of stone terrace walls were constructed by past societies in the dry valleys of the central Negev highlands to capture runoff/floodwaters from local rainfall to enable agriculture in the desert. Human intervention in geomorphic processes led to human-made geodiversity, as significant differences developed between terraced and natural stream channels. The former are characterised by soil aggradation, as terraced fields also captured sediment during each rainfall/flood event. The natural stream channels, on-the-other-hand, often experienced erosion and desertification. The ancient agricultural terraces were abandoned about 1000 years ago, but many stone terrace walls are still intact. On the basis of fieldwork, we report new findings of sophisticated design characteristics of terrace walls. (1) Mutual friction-hold of rectangular building stones was increased by placing the longest axis parallel with the flow direction of the floodwater and orienting the second longest axis vertically in the terrace wall.(2) The gradual addition of stone layers in the terrace walls, necessary to keep the wall above the aggrading field surface, was sometimes performed in a way that resulted in a staircase construction. Thus, the floodwaters would gradually cascade down to the next terraced field, thereby preventing undercutting and erosion. (3) In larger stream channels of 4th and 5th orders, the longitudinal axis of terrace walls was sometimes constructed with an oblique angle. This was apparently performed for two reasons: (i) to lessen the impact of the floodwaters on the terrace wall and (ii) to steer the water in diversion systems further onto the floodplain.

Global synthesis of the classifications, distributions, benefits and issues of terracing

“…Evidence indicates that the ratio between riser gradient and height is important in determining the strength and durability of a terrace (Díaz et al, 2007). Yet many terraces (with some exceptions such as the one in the Negev highland; Ore and Bruins, 2012) did not take advantage of this knowledge, inducing unstable terraced slopes. So far, subjective factors (e.g., the ease to run agricultural machinery, field size, bund height, and the locations of outlet within the bund) largely determined terrace structure , making some terraces prone to severe failures (Ramos and Porta, 1997).…”

“…Terracing has been used to conserve water, alleviate flooding risks, reduce erosion, expand high-quality croplands and restore degraded habitats (Van Dijk and Bruijnzeel, 2004;Bruins, 2012). More recently, this practice has been found to improve other ecosystem services (ESs), such as carbon sequestration, food security as well as recreation (Ore and Bruins, 2012;Garcia-Franco et al, 2014).…”

Effects of land use changes and soil conservation intervention on soil properties as indicators for land degradation under a Mediterranean climate

“…The land tenure system, land fragmentation and the cost and/or benefit of implementing soil conservation interventions have also had a significant impact on land degradation (Bizoza and de Graaff, 2012;Tesfaye et al, 2014). The Mediterranean region has been affected by anthropic disturbance for thousands of years (Ore and Bruins, 2012) and, currently, is one of the most significantly altered hotspots in the world Falcucci et al, 2007).…”

Effects of farming terraces on hydrological and geomorphological processes. A review

“…Spain (Gallart et al, 1994;Douglas et al, 1994;Cerdà, 1998;Lasanta et al, 2001), Italy (Brancucci and Paliaga, 2006;Mauro, 2011;Tarolli et al, 2014), Germany (Loczy, 1998), Israel (Ron, 1966;Ore and Bruins, 2012), Peru (Inbar and Llerena, 2000;Posthumus and de Graaff, 2005), México (Mountjoy and Gliessman, 1988), Nepal (Gardner and Gerrard, 2003), Yemen (Pietsch and Mabit, 2012), Indonesia (Sutikto and Chikamori, 1993), China (Quine et al, 1999;Cao et al, 2013), Kenia (Winter-Nelson and Amegbeto, 1998) and Ethiopia (Amsalu and de Graff, 2007), among others, have large areas of farmland covered by terraces. The significant number of scientific publications and the recent organisation of two international conferences (the First World Conference on Terraced Landscape, held in 2010 in China, and the second one held in 2014 in Peru) confirm the importance of terraces as an integrated system of land and natural resource management.…”