**7. References**

210 Soil Erosion Studies

hay mulching, different mats, nets made from jute or coco, three-dimensional mats etc. With the first series of trials, we were not able to work out differences between the materials. But a comparison can be made to results gained from field trials in South Tyrol (Waldner 1999, Graiss 2000). There, erosion was measured for different application techniques with and without covered soil surface, regarding to precipitation. A measurement of surface runoff was not possible. However, differences between the used techniques with covered soil surface (straw, hay, with or without bitumen emulsion to glue the organic matter) were low. The proportion between soil losses of covered plots to hand sowing plus cover crop

Our assessment on vegetation cover of the plots showed, that under average conditions of high altitudes the necessary minimum vegetation cover between 70 % and 80 % can be reached the second vegetation period at the earliest. This requires application techniques

During the second vegetation period, differences between used application technique are still visible but a satisfying developed vegetation cover reduces the total surface runoff and

Due to the faster germination and early growth of commercial varieties, an increase of surface runoff and soil losses the weeks after sowing was expected for indigenous seed mixtures. However, the harsh conditions in high altitudes (low soil and air temperature, short vegetation period, frequent frost), causing environmental stress to the vegetation, reduced the competitiveness of commercial forage grasses and herbs and neutralized their greater productivity. Results obtained did not show substantial differences between seed mixtures on erosion processes during the first weeks after restoration. However, to reach sustainable vegetation with a cover exceeding the minimum requirement of 80 %, the use of

The use of cover crops and nursery grasses did not have positive influence in view of a necessary reduction of surface runoff and soil losses during the first weeks after restoration. The environmental stress compensated also their capability of fast early growth, reducing

The comparison of hydroseeding to a simple hand sowing plus cover crop showed comparable results. This at least indicated a big risk in using this application technique in

A general comparison of all used application techniques during our assessments showed clear results. Only an additional cover of soil surface was able to reduce surface runoff and soil losses to an acceptable degree. Straw mulching as well as hay mulching, different mats, nets made from jute or coco, three-dimensional mats etc. could be applied. The use of application techniques with a satisfying additional cover of soil surface should be generally

The erosion trial was part of the project "Seed propagation of alpine species and their use for restoration of high altitudes in the Alps". The work of the whole project was supported

(average proportion of 1:110) is comparable to the results of our project.

with sufficient protection of soil surface for the first vegetation period.

**5. Conclusion** 

soil losses to an acceptable degree.

the positive effects towards zero.

**6. Acknowledgements** 

indigenous seed mixtures would be a precondition.

high altitudes without additional protection of soil surface.

recommended for restoration of slopes in high altitudes.

by the European Commission (FAIR CT98-4024).


**11** 

*Philippines* 

*Mapua Institute of Technology* 

**Combined Hydroseeding and Coconet** 

**Reinforcement for Soil Erosion Control** 

Mervin M. Cereno, Fibor J. Tan and Francis Aldrine A. Uy

Soil erosion is a worldwide problem that washes away fertile farmlands, slopes of roadway cuts and embankments, produces undesirable deposits in rivers and reservoirs, and at a larger scale result to landslides (Kothyari, 1996 and Thakur, 1996) . Soil is eroded by water and wind (Toy, et.al, 2002). In tropical countries like the Philippines, precipitation is high and erosion by water is the dominant driving force based reported cases. Protection of soil

To protect the soil surface from erosion, it should be protected from direct contact with erosive forces. Plant cover helps protect the soil surface and provide supplemental soil stability (Morgan, 2005). Hydroseeding is an innovative method of growing vegetation and is designed for slope protection. In the Philippines, its effective application is showcased in

Another green technology being used is the application of coconut coirs or coconets. Coconets helped stabilize the slope and improved the growth of vegetation in pilot projects

Newly planted vegetation on slopes could be easily washed away by heavy downpour of rain. Erosion of the slope and replanting of vegetation would be a costly consequence. Coconets, on the other hand, will show its full potential if coupled with a good growth of vegetation. Artificial vegetation is needed to facilitate the even growth of plants. Attempts of combining coconets with vegetation were done using grass (vetiver grass) and trees

Limited and very little information about hydroseeding is available since it is newly introduced in the Philippines. Tests to assess this method were only made by private construction companies which makes the data's exclusive only for the company's use. The use of combined hydroseeding and coconets in slope protection was investigated in this study. The study was aimed to assess the effectiveness of the combined technologies to

The research involved an outdoor component of the experiment to facilitate growth of vegetation. Transportation of each representative slopes to the laboratory was by means of a forklift to minimize disturbance. To further minimize the disturbance factor, the test boxes were transported carefully. Only one type of soil, degree of slope and the intensity of rainfall were considered. However, results were captured at different times in the entire duration of

**1. Introduction** 

surfaces especially of slopes is needed…

the Subic-Clark-Tarlac Expressway (SCTEX) Project.

(Madre de Cacao and neem tree) (DPWH, 2005).

the rainfall simulation.

of the Department of Public Works and Highways (DPWH).

control soil erosion in a representative slope at different series of tests.

