Based on the analysis of the river Ao Khiao, river crossing reveals to be a difficulty for humans and animals. Floods destroy river edges. As a result, the gap between river banks increase. Water dynamic and Fig Ficus tree’s development will be used as design tools to increase dynamics of the wildlife river crossing. The development of stream corridors will improve the access of rainforest habitat. The observation point and the bridges will support animal’s conservation, and will be important spot of animal observation leading to tourism development.
Moreover, during rain seasons, floods are at the origin of destructions of cities down below the valley. Frequency and severity of flooding increase, becoming more and more violent, provoking extreme damages due to debris carry by the river. The river bridge will create a filter to obstruct the movement of large destructive materials, and slow down the river stream. The water dynamic will be used to construct and set up a semi natural bridge made of the same destructive material.
Pathways through the forest leads humans and animals to crossing points. Crossing points have been chosen because of their characteristics such as low slopes, close river banks measuring 20 meters, and composition, made of granit stones deposed and dead wood debris. They are located in the middle reaches of the mountain, between 400 meters and 600 meters of altitude. The ideal spot is characterized by the presence of transported material, debris and granit rocks and tree‘s trucks accumulated.
Bridges design is based of the analysis of rainforest species.
At first, instream and river banks species will be able to rise the river. They will be constitute by aquatic plants for micro-invertebrates, amphibians, fishes and reptiles. Short passages with low width will allow them to cross. The canopy layer will be built for insects, birds and semi arboreal mammals where they could found food like figs. Animals play an important role, spreading the seeds of plants in the forest. Flowers and fruits pollinisation depends on animals to survive. Medium and large sized mammals used mainly the floor layer. They like tall grass and trees to hide. Most of forest animals are the insectivores. Predators of the forest are attract by other mammals like deers. They need large and high structures to cross.
As conclusion, crossing points will be design considered wildlife ’s characteristics such as : ways (ground floor, canopy layer, air, river edges and stream) light (nocturnal animals living during night or sunset/sunrise, wakes up to find food) texture (ground, grass, talls grass, trees, branches, water) dimensions (long, large, with low or high width, or high crossing passage) attract by ( fruits, flowers, texture, sound, light, smells, animals, plants)
On one hand, on the ground floor layer, large mammals and high mobility medium sized mammals will cross, such as elephant, deers, tigers or tapir. On the other hand, on the canopy layer, 50% of the rainforest animals can be found, containing the majority of the rainforest’s wildlife.
Bridges will evolve, from the creation to the destruction.
The existing river site is made of granit stones, deposed and carry by natural processes of erosion and accumulation of materials. Seasonal disturbance characterized by rain season covers the site by floods. River bed mesures 60 meter large. Floods increase distance between banks, destroying aquatic and river edge habitats. As consequence, the canopy layer is barely connected. Dead trucks will be carry and disposed all along the edge river.
After 6 months, dead trucks are gathered. Local communities and rangers build the river bridge with materials coming from river’s edges destruction. Dead trees‘s length is between 10 and 20 meters long. Rocks are moved and laid on the river banks. Granit rocks should mesure 5 meters and not weigh more than 400 kilograms. The transport will be made by pushing rocks with steel bars.
Trucks are put in place and disposed at 15° degrees relative to the river stream. Dead woods block debris going down the stream. At the end, river bridge is built up by the accumulation of debris transported by the river, such as smalls granit stones, dead trees, branches and sediments.
After a year, the river bridge slows down the river stream, allowing edges resilience and river banks to reconstruct. It creates stream pools, bringing sediments, minerals and favorise growth of plants and aquatic habitat. But it could collapse and break under the influence of another extreme floods episodes.
Using the cables as a support, roots of Fig Ficus tree are branded and attached. Cables are hanging up to trees at 15 meters high. Roots grow from 1 cm to 40 cm of diameter. The steel cables have a diameter of 1 cm. Fig Ficus roots are branded to the cables helped by the community. Then, the first strings branded develop. Epiphytes will support captation of humidity by their roots. The hanging living bridge of branded roots is completed.
After 10-20 years, habitats develop. River bridge will increase the instream, aquatic and edges habitats, destroyed by heavy floods. Floods carry sediments and minerals, creating salt lick on the riparian part of the river. The construction of the living bridge will help to connect forest habitat together, home of mosses, flowers and epiphytes.
Ecological infrastructures for wildlife observation will be developed by using semi-natural processes, and take place in two different temporalities.
On the ground layer, the river bridge has a seasonal dynamic, influenced by the wet season and floods. On the canopy layer, using Khian tree and Fig Ficus tree, the living bridge and the observation point are projects which are going to take decades to achieved.
The living observation point is built with the same technique as the living bridge, with fig ficus roots. Khian tree is the support of young Fig Ficus tree. Khian tree is a 30 meters tall tree and 15 meters of width. Branches are separate at 60°. The observation point is located at 18 meters from the ground. The structure mesures 6 meters per 6 meters. First strings are branded helped by the community. Roots are guided to construct the roof. Living observation point of branded roots of fig ficus tree is construct on a Khian tree.
The best moment to observe animals is during the night, when the bridge is active. Tourists could come and see the wildlife activity.