meters long and a meter wide(Fig.03).
“Th e mat itself acts like a mulch, so you prevent any weeds growing up through it that might already be within the bank material. But more importantly, when the banks become inundated, you get fine sediment trapped within the coir. Th at helps to bind the roots and feed the plants,” says Ian.
3 Banking on Tomorrow’s Seedlings
Creating a sustainable riverbank ecosystem means using native species. So before the banks were scraped back, seed was collected from suitable native aquatic species-a process managed by Atkins -and stored in a seed bank. Some of this seed was then used by bioengineering and nursery specialists, Salix, who were appointed by the Olympic Delivery Authority to cultivate plants off site in what’s believed to be one of Britain’s biggest-ever nursery contracts.
The offsite growing operation was huge and sowing for the project commenced in June 2009, as plants must be a year old and well established in their coir pallets before encountering the tough riverbank environment.
Plants for the wet woodlands, including sedges, were raised in more than 7,000 pots at Salix’s nursery on the Gower peninsula, near Swansea. And in Norfolk, the company created a new 16-acre nursery dedicated to the 2012 project(Fig.04). Here, more than 300,000 plants representing some 28 different species, including sedges, common reed, marsh marigolds and yellow fl ag irises, were grown on more than a thousand coir pallets, ready to be transported to London in the following months.
During the summer of 2010, the 18,000 square metres of planting were then pieced together like a giant jigsaw. This was a massive logistical challenge. To make it easier, each of the pallets and rolls was tagged. It was vitally important that each one went in exactly the right space so as to avoid cutting and trimming the roots and rhizomes of the plants. The team laid them out in blocks, to a plan, to make sure this didn’t happen.
4 Ponds and Wet Woodlands from Scratch
While the riverbanks of the “Old River Lee” occupied much of the attention of
the Atkins team, there were also entirely new bodies of water to consider. A fundamental part of the biodiversity of the river edges in the north of the Park lies in three new triangular ponds, off the east bank. Two of these were designed to dry up in the summer, forming moist grassy hollows. Th e third pond was created to retain water, enabling species such as water lilies and marsh marigold to thrive(Fig.05).
Preventing that third pond from drying out -while also ensuring that it did not fl ood along with the River Lee-was a conundrum. Atkins responded by designing a connection between the pond and the river to act as both overfl ow and feed. Flows could be regulated: when the pond level rose too high, water could be drained back into the river; when it started to dry out, a valve could be opened to release river water back into the pond. It sounds simple, but it is believed to be the fi rst of its kind for a habitat feature of this scale.
As well as the improved waterways and riverbanks, new wet woodlands will be a notable feature of the Olympic Park. They’re now a rare habitat in the UK, and the ones in the Park are being created from scratch.
“It was quite a novel thing to be asked to do,”recalls Atkins’ Ian Morrissey. “The challenge was to make sure we had the right water levels within the wetwoodland areas. Atkins was responsible for working out the topographies and the channels, and how they would interact with the river.”
Wetlands have a tendency to become dry land eventually, a process that can be slowed down through selecting the right vegetation, careful water level management and maintenance.
“The sedge species we selected were chosen because they are quite vigorous so are able to compete well with terrestrial species,” says Ian.
Tree species for the wet woodland include willow, alder, birch and the now rare black poplar, points out Atkins’ Mike Vaughan: “It’s fantastic for wildlife. You get a lot of invertebrates in there, as well as nesting birds.”
Birds, though, can present a challenge, particularly on the freshly planted riverbanks.
“There’s a risk of wildfowl grazing our plants when they get on site,” says Mike. To prevent that happening, hundreds of meters of deterrent fencing were erected around new vegetation. That stayed there until spring 2012(Fig.06).
5 Beyond the Finishing Line
The transformation of the lower Lee Valley and the creation of the new park, now nearing completion, is remarkable by any standards. Visitors to the Olympic Park – up to 250,000 every day at the peak of the Games – will encounter one of the greenest and most environmentally friendly parks ever to be created for the Olympics.
And the benefits will be felt long after 2012. “We’re pulling that really difficult trick of putting in infrastructure that’s good for the Games, but will work in legacy,” said the ODA's John Hopkins. “This will be a great place to live and work, with rivers and parklands at the heart. Socially, economically and environmentally, there will be a terrifi c legacy-it’s a new landscape powering a new piece of city.”
伦敦2012奥林匹克公园滨水景观设计与营造
如果在不久的未来，将有数百万人途经这块滨水区域，沿河该如何种植？如果了解到自然界中人造湿林地已十分罕见，该如何设计、创造并维护周边这种湿地环境？该如何长期保持栖息地的活力和可持续性？在伦敦2012奥林匹克公园项目中，来自阿特金斯的工程师们受托负责湿地和河滨地区设计及建设，将会找到所有这些问题的答案。
为2012年伦敦奥运会和残奥会而新建的奥林匹克公园是由一片废弃工业用地改造而成，占地超过246hm2，是欧洲最大的城市景观项目之一。东伦敦下利亚山谷的河流和湿地形成新的风景将是整个新公园的视觉中心，并为2012年伦敦奥运会平添景色。
阿特金斯负责河岸和湿地的软化设计，以及河岸修复和生物工程。从项目的概念设计到施工建成，阿特金斯的工程师们发挥了重要作用。该项目不仅仅修复了超过8km 长的河岸，同时还修建了2hm2的芦苇地和池塘和9000m2的珍稀湿林地。这样的河岸改造力度可谓史无前例（图01）。
项目的挑战在于要使人们从观、行两方面都能有更好的亲水体验，因此设计要让河流更具可达性和开放性，并由此成为公园的焦点景观。
迈克·沃恩领导了阿特金斯的多学科设计团队，其中包括河流工程师、地貌学家和生态学家。“我们希望通过调整陡峭的斜坡来打开河流廊道，”迈克解释，“坡度降低后，河水被引入公园，也更具可达性。人们可以近距离靠近河边，观察这里到底发生了什么。”
精确的河堤几何处理是一门微妙的平衡艺术。河堤若太陡，河岸的人工加固成本将高居不下；河堤若太浅，河流会开始侵蚀场地上宝贵的空间。最终设计采用的坡度为1:2.5，约为22°。河堤的占地空间则受限于疏导洪水、陆地景观和基础设施的需要。因此，对于过度陡峭的河堤采用了两种办法：第一，尽可能地用椰皮纤维卷和木桩沿斜坡堆垒河提；对于一些坡度达70°的河堤部分则采用加固手段，设计了多层土工格栅和钢丝网笼，表面覆以草皮。
如今，新的景观正在迅速成型，利亚山谷的旧貌已难觅踪迹。在2006年伦敦奥运交付管理局拿到这块土地之前，这里的河道纵横交错，被入侵的杂草所阻塞，还有旧购物车和汽车轮胎等城市废弃物被随处丢弃。
利亚山谷中没有被好好照管的河道网络不仅仅是城市的“眼中钉”，更成为了“绊脚石”——它将西面的哈克尼区（H ackney）和陶尔哈姆莱茨区（Tow er H am lets）与东面的沃尔瑟姆福雷斯特区（W altham Forest）和纽汉区（N ew ham ）分而隔之。
现在，重新焕发生命的水路以及横跨其间的新交叉点，不论在赛期还是2012年之后都将十分重要。它们是遗赛后规划方案的一个主要部分，将新公园及其水网与东伦敦大范围内的规划布局连接起来。
1 栖息地再焕生机
伦敦奥运交付管理局对奥林匹克公园寄予厚望，希望场地中大部分河流和自然特征都能创造可持续的栖息地。但是要将杂草和垃圾填塞的河谷转变为其最初
的原始状态，是一个漫长而艰难的过程。
阿特金斯的工程师们先深入了解场地上盘枝错节的河道水路，并在一定时间内对不同地点的水流量和水速进行监测，将收集的数据构建了一个精细的水力模型，用以预测洪水风险。这点极其重要。因为阿特金斯承担着场地上平均海面（海平面）4m 以内的所有责任。
在环境影响评估阶段，洪水风险的充分评估就已展开。分析不仅包括了由于频繁降雨造成的雨洪，还考虑了由于潮汐变化和蓄水所造成的水位自动调节。2008年期间，河道系统进行了蓄水，使得建模过程相当复杂。实际上，尽管蓄水削弱了潮汐对泰晤士河的直接影响，但间接影响仍然存在。“当潮汐来临，它会阻碍河水排出李河。”迈克·沃恩解释，“因此，水位一天的变化能达到平均400m m 。”
阿特金斯的模型计算准确地预测到了这一现象，以及由此增加的洪水风险。“这些发现带来了景观轮廓上的改变。” 迈克说，“沿河道路被抬高了1m ，同时对湿地的轮廓也做了抬升。对于它们的生存而言，保持正确的水位十分关键。”
公园大量运用了可持续的排水技术。在景观领域，广场采用了渗水性材料，水可流入与河边池塘相连的生态洼地。此外，还采用了地面运输、地下管道和存贮等多种手段（图02）。
由于原有的河堤许多部分非常陡峭，因此河道修复的第一步就是让河堤“躺下来”。经过几个世纪不断地堆积，有的地方地平面高达10m ，堆在河堤上的垃圾有碎石、玻璃、动物骨头和更近一些时期从伦敦最东端运来的拆除的战时物品。
项目面临的另一个挑战是遍地的入侵植物，如喜玛拉雅凤仙、日本紫菀和巨猪草。这些都是19世纪由于园艺好奇心而引进英国的速生植物，却成失误之举。
入侵植物对于河堤是个坏消息。它们疯狂地繁殖、生长，驱逐本地植物，并且非常顽固。紫菀能在水泥中扎根；巨猪草含有呋喃香豆素和见阳光激活的毒素，会导致皮肤溃疡。因此清理成了优先考虑的工作——整个场地的土壤都做了处理，河堤上的所有植物被尽数铲除。
同时，阿特金斯还要保护地块上的动植物种群。2006年环境影响评估中即开展了第一阶段的栖息地调查工作，包括鸟类和鱼类的调查。同时，已着手进行了一项主要的物种迁移工作，规划了一批适宜的迁移地，包括临近公园营建的
城市规划滨水景观设计中英文对照外文翻译文献
