Area Zonation for the Application of Rain Harvesting Method in Structural Mitigation Flood at the Watershed of Bengawan Solo Bojonegoro District

PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-10 PERAN ILMU KEBUMIAN DALAM PEMBANGUNAN INFRASTRUKTUR DI INDONESIA 13 – 14 SEPTEMBER 2017; GRHA SABHA PRAMANA AREA ZONATION FOR THE APPLICATION OF RAIN HARVESTING METHOD IN STRUCTURAL MITIGATION FLOOD AT THE WATERSHED OF BENGAWAN SOLO BOJONEGORO DISTRICT

Arhananta1*) Joko Purwanto1) Keni Christy Manurung1) Kenny Lekatompessy1) Muhammad Alhafiq Wahyu Nabillah1) Dr. Ir. Eko Teguh Paripurno. MT2) 1)Student of Geological Engineering of UPN “Veteran” Yogyakarta 2)Lecturer in Geological Engineering of UPN “Veteran” Yogyakarta Jalan SWK 104 (Lingkar utara), Condong catur, Yogyakarta *corresponding author: [email protected]

ABSTRACT

Flooding is a disaster for many regions in Indonesia. Bojonegoro is a district which every year has a high flood threat. The cause of flood from the reviewed through google earth imageryry, meteorological data, maps of topography, and hydrological data such of extents, discharge, and other data about watershed Bojonegoro. Area of Bojonegoro flood occur due to overflowing of bengawan solo rivers which the morphological is meandering river and have formed a bottle neck in the shape of the body area of the river. Sandbar river, meander scars, and oxbow lake on the imagerys which can be interpreted that the watershed of Bengawan Solo river part of Bojonegoro is the old stadia of which dominant the deposition of the erosion, and erosion running horizontally which allows shallowing the rivers. The average level of precipitation thatrelatively high and volume capacity reductions of the watershed makes flooding occurs every year. Rain harvesting method is the method of structural mitigation based on ecohydrology. Rain harvesting system has three basic elements that is namely the area of collection, conveyances system, and storage facilities. In this research emphasized at the elements of the collection area and flood prevention in the district of Bojonegoro which is the zonation area for application method of harvesting rain are in the headwater to the watershed of river solo Bojonegoro. The Application of zonation based on the composition of the constituent rocks and slope. Placing of rain harvesting methods applied in the watershed of bengawan solo that composed by loose material of sand to gravel, sandstone, and coarse grained of sedimentary rock, and placement in areas that have a flat to gentle slope.

Keywords: Flood, Ecohydrology, Strutural Mitigation, Rain Harversting.

1. Introduction 1.1.Background Indonesia is an archipelago state situated on the equator which is geographically flanked by continent of Asia on the north and the continent of Australian on the south which resulted in Indonesia having two seasons, the dry season and the rainy season. On both sides of the season, Indonesia is experiencing problems of drought during the dry season and flooding in the rainy season. In general structural mitigation will be built reservoir or embung, but in this paper will be handled with the principle of ecohydrology using rain harvesting method. In this paper focuses on the handling of flood disaster in Bengawan solo district of Bojonegoro.

1.2. Flood Definition of Flood Disaster According to Law No.24 of 2007, disaster is defined as an event that threatens and disrupts the lives and livelihoods of the people. Disasters can be

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PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-10 PERAN ILMU KEBUMIAN DALAM PEMBANGUNAN INFRASTRUKTUR DI INDONESIA 13 – 14 SEPTEMBER 2017; GRHA SABHA PRAMANA caused by natural factors and / or non-natural factors nor human factors so it emergence of human fatalities, environmental damage, property loss, and psychological impact. Flooding is defined as the inundated somewhere due to overflow of water that exceeds the drainage capacity in a region and causes physical, social and economic losses (Rahayu et al, 2009). Flooding is a seasonal threat that occurs when the body of water overflow channels that exist and inundate the surrounding area. Flooding is natural threats which often occur and most disadvantageous, both humanitarian and economic (IDEP, 2007). Simply the flood can be defined as the presence of water in a large area so that covers the earth's surface area. Particularly in Bojonegoro, floods are the most frequent disasters and be the cycle That goes on during the rainy season. The cause of the floods that occurred in Bojonegoro due to floods from the watershed before the city of Bojonegoro nor heavy rain that flushed during the rainy season. According to (Dwi ratna putri, et al 2010) in the journals of the conservation directives of Bengawan Solo river area through urban areas that the area of the Solo River solo through Bojonegoro Urban is 34.3204 km2. The characteristic of Bengawan Solo River of Urban has a length of 18.9 km with a slope of the river flow of about 1: 10,000, the width of the river is approximately 150 meters with the depth of 7 meters.The maximum river capacity ranges from m³ / sec to 1,800 m³ / sec. The result of mononobe analysis calculation from rainfall data which used to calculate peak discharge of river water and it can be knownthat there is an increase of river water discharge every year. According to (Bobby Arina Rizki, 2014) in the journals of characteristic analysis of bengawan solo river declare the extreme annual rainfall in the watershed of the headwaters of Bengawan Solo river causes the stream flow discharge which is large in several tributaries between Bendung Colo, Sukoharjo up to Jurug, Surakarta.The amount of flow discharge found in each varies of tributary with each occurrence of large rain depending on which sub-watersheds there are rainfall. The characteristics of river flood hydrograph (lateral inflow) and flood travel time from upstream to downstream of the study can be identified by simulation of some occurrence of rain. This research aims to know the flood characteristics in the River of Bengawan Solo Colo Bendung Area - Surakarta City.The first step in this research is the unit of hydrograph analysis and preliminary analysis of the watershed parameter. Then, the hydrological model was compiled using HEC-HMS program to calibrate the watershed parameter against the occurance of rain and real time flow discharge so obtained the optimum parameter representing the watershed characteristics.Using the optimum of watershed parameters which obtained, simulation of some occurance of rain can be done. The results of this research indicate that the flood characteristics in the Bengawan Solo River Bendung Colo - Kota Surakarta is affected by the lateral inflow of the tributaries in the watershed, with the dominant tributaries being the Dengkeng and Samin Rivers.

1.3. Ecohydrology Ecohydrology is a new paradigm which is a combination of hydrology and biota dynamics in the catchment area to be applied in solving environmental problems (Zalewski et al., 1997). Vivile & Littlewood (1997) emphasize ecohydrology as a combination of biological sciences and physical sciences in an effort to be more understanding about ecosystems.Vivoni (2003) states that ecohydrology studies focus on the relationship between ecosystem patterns with soil moisture, climate and soil; As well as the role of vegetation in water balance, surface flow energy. UNESCO (2004), states that the concept of ecohydrology is based on 3 principles, namely framework, target and methodology. The concept of ecohydrology with a scientific approach that takes into account the interaction of abiotic and biotic aspects is formulated into three principles and one of the following theories:

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PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-10 PERAN ILMU KEBUMIAN DALAM PEMBANGUNAN INFRASTRUKTUR DI INDONESIA 13 – 14 SEPTEMBER 2017; GRHA SABHA PRAMANA The principle 1, the hydrological aspect, concerns the abiotic structure of the river system, the dynamics of hydrological processes, and the specific spatial-temporal impacts of human intervention; Principle 2, which is ecological integrity, involves inter-relation of ecosystem components showing the potential and capacity of ecosystem in producing environmental products and services; and Principle 3, ecotechnology, concerns the use of information and knowledge about abiotic and biotic aspects (from principles 1 and 2) for the development of new ecotourism biotechnology and hydrological system solutions that can enhance ecosystem capacity in producing environmental products and services. Zalewski (2010), stated that the implementation of the concept of ecohydrology as an integrated watershed management tool can be done with the following four steps: (A) monitoring threats by methods of hydrological quantification; (B) assessing causal relationships with analysis of ecological patterns and processes; (C) develop ecohydrological methods with ecotechnology using points (a) and (b) to increase the production capacity and ecosystem environment services; and (D) develop an integrated system solution by integrating the abiotic, biotic, and institutional socioeconomic aspects.

According to (Pawitan and Haryani 2011) the needs for ecohydrology research in Indonesia as follows: - Research on trophic level (trophic level) in terms of balance between producers and consumers in a lake or reservoir, and their relation to the water level - Research in ecotonic areas between biota and water fluctuations - Research and development of aquatic zonation - Research development of riparian areas - Research on improving water retention capability related to the environment - Research fito technology to solve the problem of environmental pollution - Urban ecohydrology research (rural ecohydrology) - Ecohydrology research in the delta - Research related to flood and drought

1.4. Rainwater Harvesting According to Janette Worm and Tim van Hattum (2006), rainwater harvesting system consists of three basic components namely, catchment area, delivery system and storage reservoir. Catchment area or a place where the first rainwater is collected or collected, for example the roof surface. Delivery System, is a system that drains rainwater from catchment area to storage (storage). While the storage reservoir is where the rainwater accommodated until the water is used for various purposes. Norma Khoury-Nolde (2002), divides Rainwater Harvesting into several types. First, the Occasional Type, ie water is stored for a few days only, in small containers. This type is suitable when the rainfall pattern is same with several days without rain and when there is a reliable alternative water source. Intermittent type, used in situations with a long rainy season when all water needs are met by rainwater. During the dry season, water is collected from other sources. Furthermore, the Partial Type, in this type, rainwater is used throughout the year but the harvest is not sufficient to meet domestic needs. For example, rainwater is used for drinking and cooking, while for other uses (eg bathing and washing) using water from other sources. The latter is the Full Type, used year-round, the water for domestic use is

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PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-10 PERAN ILMU KEBUMIAN DALAM PEMBANGUNAN INFRASTRUKTUR DI INDONESIA 13 – 14 SEPTEMBER 2017; GRHA SABHA PRAMANA entirely derived from rainwater. In this case, there is usually no alternative water source other than rain water. Mrs. S.D. Khandagale and Mrs. V.A. Joshi stated that there are several components that must be considered in making Rainwater Harvesting system, namely hydrogeology, land use pattern, and hydro-meteorology. Hydrogeology includes the nature and level of aquifer, soil cover, topography, depth and groundwater quality. Land use patterns such as land used for industry, housing, green open spaces, etc. Hydro-meteorology includes the pattern, duration and intensity of rainfall. According to Patricia H. Waterfall (2004), Rainwater Harvesting has several benefits among others, reducing the use of drinking water in other household necessities such as bathing and washing, rainwater is a clean water that goof for plants, can prevent dryness in plants, due to rain water that seep into the soil will reduce the accumulation of salt in the soil that can inhibit the growth of plant roots, but it can also prevent flooding and erosion. 2. Research Methods The method used is imagery interpretation, data overlay, map creation with ArcGIS software, and literature study on related research.

3. Data The resulting data are zonation map of rain harvesting method from overlay of Watershed map, contour map, DEM map, and geological map. 4. Results and Discussion The factors why Bojonegoro accur flooding beside from climatological factors there is a geological factor. The first stage of discussion is interpretation of the imagery of Google Earth Bojonegoro River watershed. Interpretation takes a form of the main stream and the formations of which has the important geomorphological significance. Then the second stage is to define the actual Landform and land use based on Google Earth Imageryry. Then in the final stages of analysis carried out aspects of geomorphology. Can be found as follows: Primary data in the form of remote sensing data GoogleEarth Imagery 2015 And 2016 is used for actual land usage intrepetation and analysis of land form of Bengawan Solo River Bojonegoro District. From Figure 4.1 it can be seen that Bojonegoro has a fine texture which can be interpreted in the area around the watershed and the North has a slope which relatively flat and then in the south it can be seen that it has a medium texture where the slope begin to appear and have a moderate slope. In the figure 4.2 and 4.3 can be interpreted that the formation of bottle neck on the body of the river is a state where the volume of the river experienced a reduction that resulted in the overflow or in the form of flood if from the river part of the bottle is fully loaded. It can be interpreted that the area in Figure 4.4 is a large water catchment area in which water fills the enclosure if overflowing. It can be interpreted that the residential area follows the direction of the river flow, especially in the cut of meander area where in case of the overflow of water, the area receives the most water delivery. Based on the all imagery in Figure Section 4 it can be concluded that the original form of the Bengawan Solo watershed of Bojonegoro is the Fluvial origin where in outline of the Bojonegoro watershed is part of the meandering river downstream of the solo bengawan river.

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PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-10 PERAN ILMU KEBUMIAN DALAM PEMBANGUNAN INFRASTRUKTUR DI INDONESIA 13 – 14 SEPTEMBER 2017; GRHA SABHA PRAMANA In the Google Earth Imagery in Section 4 it can be noted that Bojonegoro watershed is mostly floodplain and alluvial plains and has sandbars that signifies the dominance of precipitation and erosion horizontally in the area. The units of lithology in the bodies of rivers and around the river seen from their texture are unconsolidated units.

Geomorphological Aspect Analysis

Morphology: Morphography: Bojonegoro watershed is dominated by plains, winding or bermeander rivers, having a bottle neck formation on the river body Morphometry: The central to the North Bojonegoro watershed has a relatively flat slope and on the south it has a moderate slope.

Morfoganesa Active Morphostructure: Not developed Passive Morphostructure: Unconsolidated and weakly resistant units. Morphodynamics: Erosion and deposition in horizontal or fluviatile processes

Morfoasiosiasi From what is seen along the DAS bngawan solo Bojonegoro district is used for residential areas where in fact the area has the highest flood vulnerability. Map of this solo bengawan river watershed starts from upstream of waduk gajah mungkur Wonogiri through Surakarta-Karanganyar-Sragen-Ngawi-Bojonegoro. The watershed is bounded by red lines then by lithology through regional geological maps can be grouped into 4 zones, among others: Zone (Aluvium) (loose material) in gray, Zone (sandstone-breccia- conglomerate) with yellow color Zone (Green hats, and Limestone Zone) are blue. From the level of ability to pass the smallest to the greatest water in sequence are the Zone (napal, claystone), Zone (Limestone), Zone (sandstone, breccia, conglomerate), then Zone (Alluvium). From the map it can be found that the best zone in the lithologic aspect is in the upstream and downstream areas coupled with a wider scope than the center.

5. Conclusion In flood analysis according to the geomorphology aspect in the Bengawan Solo watershed of Bojonegoro regency it is concluded that it is a meandering river and has a bottle neck formation which also has a flat slope and is aggravated by the use of land along the river into a settlement. It is found that the best lithologic zone is in the upstream and downstream areas coupled with a wider scope than the middle. So it can be concluded that the placement of rain harvesting method is well applied in the upper watershed of Surakarta and downstream of Bojonegoro watershed.

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PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-10 PERAN ILMU KEBUMIAN DALAM PEMBANGUNAN INFRASTRUKTUR DI INDONESIA 13 – 14 SEPTEMBER 2017; GRHA SABHA PRAMANA Acknowledgements

Thanks to Mr. Ir. Eko Teguh Paripurno, MT. Who has opened our minds as a student to get an idea in with something new. Then, thank you to the colleagues of the Pangea Cruiser nature activist "Tambarta" who are always there to help with the work of this paper.

References Anon.. (2013). Rainwater harvesting. Water Aid, pp. 1-10. H. Waterfall, P.. (2006). Harvesting Rainwater For Lanscape Use. University of Arizona , Arizona. Khandagale, S. & Joshi, V., n.d. Rainwater Harvesting: Grab hold of Water Where it Falls!. Thane, MS, India, V.P.M’s Polytechnic, pp. 1-9. Khoury-Nolde, N., n.d. Rainwater Harvesting. Jerman, fbr, pp. 1-10. Pawitan, H.. (2011). Konsep ekohidrologi sebagai paradigm baru pengelolaan. Jakarta, s.n., p. 11. Putri Ratna Dwi,dkk. (2010). Arahan Konservasi Wilayah Bengawan Solo yang Melalui Perkotaan. Universitas Brawijaya, Malang Ramadhani,dkk. (2016). Analisis Pencemaran kualitas air sungai bengawan solo akibat limbah industri di kecamatan Kebakkramat Kabupatren karanganyar. Universitas Muhammadiyah Surakarta. Rizky A. Bobi. (2014). analisis karakteristik sungai bengawan solo. Universitas Gadjah Mada Prasetya Herry. (2014). Kualitas Perairan Sungai Bengawan Solo di Wilayah Kabupaten Bojonegoro Berdasarkan Indeks Keanekaragaman Plankton. Universitas Negeri Surabaya Soeprobowati, T. R.. (2010). Ekohidrologi Konsep Pengelolaan Lingkungan Berkelanjutan. Indonesia, s.n. Worm, J. & van Hattum, T.. (2006). Rainwater harvesting for domestic use. Wageningen, Agromisa Foundation and CTA, pp. 1-84.

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