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Drainage divide migration alters the geometry of drainage basins, influencing the distribution of water, erosion, sediments, and ecosystems across Earth’s surface. The rate of divide migration is governed by differences in erosion rates across the divide and is thus sensitive to spatiotemporal variations in tectonics and climate. However, established approaches for quantifying divide migration rates offer only indirect evidence for the motion of the divide and provide only migration rate averages. Consequently, transience in divide migration cannot be resolved, hindering the ability to explore environmental changes that drive the dynamics of such potential transience. Here, we study a set of datable terraces identified as markers of paleo-divide locations, which provide direct evidence for the paleo motion of the divide. The location and age of the terraces reveal intermittent divide migration at timescales of 10⁴to 10⁵y, with phases of rapid migration—at rates more than twice the average—which coincide with documented regional paleoclimate fluctuations. These findings highlight the intermittent nature of divide migration dynamics over geomorphic timescales and its potential sensitivity to climate changes, underscoring the impact of such changes on the planform evolution of drainage basins. 

Abstract. The width of valleys and channels affects the hydrology, ecology,and geomorphic functionality of drainage networks. In many studies, thewidth of valleys and/or channels (W) is estimated as a power-law function ofthe drainage area (A), W=kcAd. However, in fluvial systemsthat experience drainage reorganization, abrupt changes in drainage areadistribution can result in valley or channel widths that are disproportionalto their drainage areas. Such disproportionality may be more distinguishedin valleys than in channels due to a longer adjustment timescale forvalleys. Therefore, the valley width–area scaling in reorganized drainagesis expected to deviate from that of drainages that did not experiencereorganization. To explore the effect of reorganization on valley width–drainage areascaling, we studied 12 valley sections in the Negev desert, Israel,categorized into undisturbed, beheaded, and reversed valleys. We found thatthe values of the drainage area exponents, d, are lower in the beheadedvalleys relative to undisturbed valleys but remain positive. Reversedvalleys, in contrast, are characterized by negative d exponents, indicatingvalley narrowing with increasing drainage area. In the reversed category, wealso explored the independent effect of channel slope (S) through theequation W=kbAbSc, which yieldednegative and overall similar values for b and c. A detailed study in one reversed valley section shows that the valleynarrows downstream, whereas the channel widens, suggesting that, ashypothesized, the channel width adjusts faster to post-reorganizationdrainage area distribution. The adjusted narrow channel dictates the widthof formative flows in the reversed valley, which contrasts with the meaningfullywider formative flows of the beheaded valley across the divide. Thisdifference results in a step change in the unit stream power between thereversed and beheaded channels, potentially leading to a “width feedback”that promotes ongoing divide migration and reorganization. Our findings demonstrate that valley width–area scaling is a potential toolfor identifying landscapes influenced by drainage reorganization. Accountingfor reorganization-specific scaling can improve estimations of erosion ratedistributions in reorganized landscapes.