LEVEL OF LANDSLIDE SUSCEPTIBILITY IN CIBAL DISTRICT OF MANGGARAI EAST NUSA TENGGARA

This research aims to determine the degree of susceptibility of landslides in Cibal Districts. The method used in this research is descriptive survey method. The population in this research is all of the land in Cibal Districts. data collection technique is done by using observation technique and documentation study. Data analysis technique in this research uses crosstab technique. The results of this study can be seen that the level of susceptibility of landslides in Cibal based on crosstab results, there are three categories of vulnerability of landslide , they are low, medium and high. Low landslide susceptibility rate of 6.979,65 hectares or 64,09% is found in Nine sub-districts / village. The moderate landslide susceptibility rate has an area of 3.634,67 hectares or 33,38%, in seven villages. While the high landslide susceptibility rate is found only in one village with an area of 275,65 hectares or 2,35% of the total area of Cibal districts.


Introduction
Natural disasters are disasters that caused by events or events that is caused by nature such as earthquakes, tsu-nami, eruption volcanoes, floods, dry, hurricanes, and landslides.
Natural disasters can give effects on the economic, social and environmental sectors. Suripin (2002) defines landslides as a form of erosion where the transport or movement of the soil mass occurs at some point in a relatively big volume. In terms of movement, there are some erosion caused by the movement of the soil mass, creep, rock fall and mud flow. The mass that moves in the landslide is a big mass. Therefore, the occurrance of landslide will bring victims, such as environmental damage, agricultural land, settlement and infrastructure and property and even loss of human life.
According to Minister of Public Works Regulation No. 22 of 2007, the process of landslide that starts from the absorption of rain water into the soil that will increase the weight of soil. If the water penetrates to the impermeable soil that acts as a slip plane, the soil becomes slippery and the weathering soil above. It will move along the slope and out the slope. Landslide can occur if the intensity of rainfall is high, slope to steep slopes, thick weathering, rocks and geologic structure varies. Land use is less suitable with the characteristics of the land (Sutikno, 1994in Permata, 2016. Susceptibility is a condition caused by human activities (the result of physical, social, and environmental processes) that causes the increasing Susceptibility of society to harm.
The degree of vulnerability can be assessed from physical (infrastructure), social, demographic and economic susceptibility (Muta'ali, 2012). Susceptibility is the degree which society, structure, service or geographic area potentially or may be damaged or disturbed by a certain dangerous impact due to its nature, its construction, and its proximity to dangerous or vulnerable areas (Djaelani, 2008).
Susceptibility is a condition of a community group that leads or causes inability to face the threat of danger (Nurjanah, 2011: 16). According to the Regulation of the Head of National Disaster Management Agency (BNPB) No. 04 of 2008 Susceptibility is a state or behavior of people or society that causes inability to face threats or danger.
Cibal is one of the areas that often occur landslide . Recorded on March 3, 2007 occured a great landslide that cause 44 people died, 21 people were injured, 6 houses severely damaged, 500 people evacuated, along the road. There are 5 major landslide point, 14 medium landslide and 12 small landslide and total broke road. In 2016, there were 13 landslide occur in Cibal sub-district which resulted in 14 damaged houses and also many people who suffered injuries . Then, there were 11 major landslides and 4 moderate landslides (BPBD Manggarai Regency, 2007, 2016

The Methods
The location of this research is in Cibal District of Manggarai Regency East Nusa Tenggara which is astronomically located between 8   Population and settlement density data were obtained from the Statistic Central Bureau of Manggarai Regency. Population density and settlements were classified into three classes. They were low, medium, and high class. To know the class interval of population density and settlement, it is used formula: Exp : C = Estimation of Class Amount (Low, Medium, high) K = Class Amount Xn = Highest Value X1 = Smallest Value Source : (Supranto, J, 1996 ) After population density and settlement, the two parameters are classified again into three classes . the classes are low, medium, and high class. To know the class is used calculation in crosstab, as follows :

Population Density
The existence of the population is one of the parameters. It is very important in setting the level of susceptibility of landslides because community is a distinguishing factor determining whether the disaster landslide can be categorized as a disaster or just as a natural phenomenon.

Settlement Density
The density of settlements has an effect on the susceptibility of landslide is the addition of load on the land which is in high danger zone so with the addition of this load can potentially the occurrence of landslide. The density of the settlement is the number of houses, schools, and other buildings on a certain land area expressed in units/km 2 .
Classification of settlement density equal to population density is divided into three categories; low, medium, and high. The calculation of settlement density classification also uses the same formula as population density. From the formula , it can be obtained the number of classes is 19 so it can be known classification category, as follows:

Landslide Susceptibility
After knowing the condition of population and settlement, so it can be counted density of population and settlement in every Village. The calculation is divided into three classes. The classes Low, Medium, and High class. To search the landslide susceptibility class using Crosstab, it can be seen in table 7 below:

c. High landslide susceptibility level (H)
Areas with high landslide susceptibility have a high or large influence on landslides. Population density and high settlement make the area classified as having high susceptibility. Population density in this area ranges from 461 -615 soul/km 2 while the density of settlements ranges from 58 to 76 units/km 2 . The high landslide susceptibility rate is found only in Rado Village. The high landslide susceptibility area is 275,65 hectares or 2,35% of the total area of Cibal Districts.
Based on the analysis of landslide susceptibility level, the distribution can be seen on the map below: