Northern brazilian river deltas: River impacts versus pristine discharge

目前，我们观察到了S·弗朗西斯科河口水文沉积学状况的基本变化。通过在沿河水库修建大坝，切断了河流泥沙向海岸带和大陆架的输送，引发了以前以波浪为主的三角洲向河口的转变。目前对泥沙供应的抑制已经使河口的泥沙收支出现了巨大的赤字，包括海岸侵蚀对小村庄的破坏。这一基本变化的水文和泥沙动力学将在全新世海岸演化的框架内进行研究。为了更深入地了解控制S·弗朗西斯科三角洲向河口转化的主要海岸和陆架过程，将调查原始的以波浪和潮汐为主导的帕尔尼亚巴河三角洲的实际动力学和全新世演化。帕尔尼巴河是介于里约热内卢São弗朗西斯科和亚马逊之间的最大三角洲。将在里约帕拉/托坎廷斯潮汐和波浪占主导地位的河口研究同等规模河口的纯河口条件。对三个河口系统的水动力、沉积物动力学和晚全新世演化的详细比较研究提供了独特的机会，以评估在以波浪和潮汐为主的环境下，切断河流沉积物供应对海岸和陆架沉积的影响。

At present we observe a basic change in the hydro-sedimentological regime of the São Francisco river mouth. The shut-off of riverine sediment transport to the coastal zone and continental shelf by constructing dams for reservoirs along the river initiates a switch of the former wave-dominated delta to an estuary. Ongoing suppression of sediment supply has produced already significant deficits in the sediment budget at the river mouth including destruction of small villages by coastal erosion. Hydro- and sediment dynamics of this basic change will be investigated in the framework of Holocene coastal evolution. To gain more insight into the principal coastal and shelf processes governing the turnover of the São Francisco delta to an estuary, actual dynamics and Holocene evolution of the pristine wave- and tide-dominated delta of the Parnaíba River, the largest delta between the Rio São Francisco and the Amazon, will be investigated. Pure estuarine conditions at the mouth of a river of the same magnitude will be studied in the tide and wave dominated estuary of the Rio Pará/Tocantins. Detailed comparative studies of hydrodynamics, sediment dynamics and late-Holocene evolution of the three river-mouth systems provide the unique opportunity to evaluate the effects of the shut-off of riverine sediment supply on coastal and shelf sedimentation in wave- and tide-dominated settings.