Conducted by ERDB
Completed on 2012
Completed
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Riparian zone as an integral component of watershed riverine ecosystem has a significant influence to hydrological system. Thus, it becomes one of the important factors influencing watershed performance. By definition, riparian zone is the lands bordering surface waters; under natural conditions these zones represent a transition from aquatic to terrestrial ecosystems. In this regards this project generally aim to evaluate the effectiveness of various riparian zone/steam bank rehabilitation measures in minimizing erosion and sedimentation of watersheds.
The study was conducted in six (6) regions which includes: Dipalo watershed, San Quintin, Pangasinan in Region 1, Pinagbalitukan Subwatershed, Diadi, Nueva Vizcaya in Region 2, Pinulot Watershed, Dinalupihan, Bataan in Region 3, Binahaan Watershed, Pagbilao, Quezon in Region 4A, Maasin River, Maasin llo-ilo in Region 6 and Kauyas River, Sal-angan, Ampucao., Itogon, Benguet in CAR.
The activities undertaken includes: 1) selection of sites; 2) assessment of watershed and Riparian zone characteristics; 3) land use survey and mapping; 4) climatic data and establishment of raingauge; 5) establishment of pilot riparian zone demo area for rehabilitation protocol and erosion plot studies and data analysis.
There were several species tested for restoration and management of riparian zone and these are: vetiver ( Chrysopogon zizanioides ), lantana ( Lantana camara ), talahib ( Scharum spotaneum ) for Region 1, guava ( Psidium guajavas ), citrus ( G. microcarpa ) and bugnay ( Antidesma bunius ) for Region 2, heliconia ( Heliconia psittacorum ), chinese malunggay, vetiver ( Chrysopogon zizanioides ) for Region 3, Chinese bamboo ( Bambusa thoracicus ), heliconia ( Heliconia psittacorum ) and lemon grass ( Cymbopogon ciatrus ) for Region 4A, vetiver, ( Crysopogon zizaniodes )Chinese bamboo ( Bambusa dolichoelada ) and Langkawas ( Alpinia officianarum/Alpinia galangal ) for Region 6 and vetiver grass ( Chrysopogon zizanioidesz ), tiger grass ( Thysanolaena latifolia ) and chinese bamboo ( Bambusicola thoracicus ) in CAR. Control species such as hagonoy ( Chromolaena odorata ) and wedelia ( widelia trilobata ) also showed to naturally grown in the area.
The following are the recommendations: 1) the shrubs and grass riparian vegetation with 3 to 5 meters buffer tested in selected region which are designed to trap sediment should require proper maintenance to remain effective rather than letting natural growth take its course; 2) the effects of varying site characteristics associated with slope, hydrology, geology and land use must be considered when determining widths when designing buffer widths for grass and shrubs; 3) the choice of species should also be considered for short term and long term management practices. Vetiver grass is proven as effective soil conservation, soil erosion control in diverse land form; however native vegetation along riparian zone should be first tested before introducing new species not native to the area. Among potential species include tanglag ( Imperata gigantia ) and wedelia ( widelia trilobata ) plant; 4) planting native species of shrubs and grass are the best management practices BMP to consider in restoring and rehabilitating riparian zone because of their adaptability and fast growing ability to colonize bare soil. However, species that thrived in various region that were considered native to the area like wedelia, hagonoy and lantana camara, and vetiver may have been invasive species. However, locals in the area reported that such species were in existent in the area for a long period of time; and 5) extreme rainfall event resulted to high erosion rate due to high interill erosion and mass movement of soil particles during cropping and maturing stage. However, with buffer strip crop planted along riparian zone, there is a reduction of 67% soil erosion rate. On the other hand, high soil build up occurrence in more than 30% slope during cropping management stage but generally reduced during maturing stage to all planted strip crops.