Habitat point records from 1988 OPRU HRE Taf, Tywi & Gwendraeth Estuaries survey

The estuaries of the Taf, Tywi and Gwendraeth are known locally as the `Three rivers` as they converge and enter into Camarthen Bay in South West Wales through a common mouth. The rivers drain agricultural catchments of 246, 1335 and 175 km2, respectively, and the underlying rocks are, for the most part slightly acidic. Of the three river estuaries, the Tywi is the larger at over 20 km in length. The Taf and Tywi are both typical coastal plain estuaries and the Gwendraeth is a bar-built estuary formed by the north westerly movement of sand from the Pembrey coast dune system. All three estuaries are presently undergoing substantial infilling by marine sediments originating from Camarthaen Bay and as a result are shallow and drain almost completely at low tide. Tidal flows within the system and in particular in the Taf and Tywi, are of considerable strength and the tidal wave symmetry is distorted producing a longer ebb than flood. This report describes the habitats and associated communities at twenty-one sites surveyed in the study area; eighteen intertidal sites and three dredge sites from the main channels. Species present have been identified and tabulated. Hard substrata communities are not well represented in the `Three Rivers` and those examples occuring are markedly sand scoured and support depauperate communities. Sedimentary habitats dominate the system, and there is a gradation of sand flats to mudflats from the mouth to the upper estuaries. The lower shore flats are generally unstable environments being subject to large tidal salinity fluctuations and strong tidal currents. More stable sand flats are found on the upper middle shore with considerably richer communities. Mussel scars occur at three sites in the system and are subject to scouring losses. Both mussels and cockles are collected commercially on a small scale and some netting also occurs. Mussel culture is presently being evaluated in the Gwendraeth Estuary. The Taf and Tywi have naturally low oxygen levels in their estuaries at times of continued fine weather, low river discharges and spring tides. These are compounded in the Tywi by effluent from a large sewage treatment works which significantly increases the biological oxygen demand (B.O.D.). The `Three Rivers` are flanked by Sites of Special Scientific Interest (SSSI) to the east, west and north. Notification of these was for the sand dune flora and fauna and maritime cliff communities. The south shore of the Gwendraeth, including Towyn Point, and Salmon Point Scar are the only marine habitats protected by the designations. The area is also of nature conservation interest for the populations of migrant and over-wintering waterfowl. Several species reach levels of National Importance, though they are not afforded any other specific site protection at the present time. rivers

泰夫、泰维和格温达斯河的河口在当地被统称为‘三河’，因为它们汇聚在一起，通过同一入海口流入威尔士西南部的卡马森湾。这三条河流分别排入246平方公里、1335平方公里和175平方公里的农业流域，其底部岩石大部分呈弱酸性。在这三个河口中，泰维河的长度超过20公里，是其中最长的。泰夫和泰维河都是典型的海岸平原河口，而格温达斯河则是由彭布罗海岸沙丘系统的西北方向沙粒运动形成的沙坝河口。目前，这三个河口正在经历由卡马森湾起源的海洋沉积物的显著充填，因此它们较浅，在低潮时几乎完全排水。该系统内的潮流流量，尤其是在泰夫和泰维河中，相当强烈，潮汐波对称性被扭曲，导致退潮时间比涨潮时间长。本报告描述了研究区域内调查的二十一处的生境及其相关群落；包括十八个潮间带地点和三个主航道疏浚地点。已对出现的物种进行了鉴定和列表。硬质底质群落在大‘三河’中并不充分代表，那些出现的例子显著受到沙质冲刷，并支撑着贫瘠的群落。沉积生境在该系统中占据主导地位，从河口到上游河口存在沙洲到泥滩的渐变。下岸滩涂通常是不稳定的生境，受到大潮汐盐度波动和强潮汐流的影响。在上中岸可以找到更稳定的沙洲，那里有更为丰富的群落。在该系统中的三个地点发现了贻贝痕迹，并受到冲刷损失的威胁。贻贝和蛤蜊被小规模商业采集，并有一些捕网活动。目前，格温达斯河口正在进行贻贝养殖的评估。在持续的晴朗天气、低河流排放和春潮期间，泰夫和泰维河的河口氧气水平自然较低。在泰维河中，这种情况因大型污水处理厂排放物而加剧，这显著增加了生物需氧量（B.O.D.）。大‘三河’东西北三面由特殊科学兴趣区（SSSI）所环绕。这些区域的通知是为了沙丘植物群和动物群以及海事悬崖群落。格温达斯河的南岸，包括托温角和鲑鱼角，是唯一受保护的海滨生境。该地区对迁徙和越冬水鸟种群也具有自然保护意义。尽管它们目前未获得任何其他特定的地点保护，但某些物种已达到国家级重要水平。