Data topography is an important data which is crucial for sustainability fungsian surface irrigation network. Measurement and topographic mapping is an activity that must be done early in the planning of surface irrigation systems. Mapping can be based on measurements in the field in full, so that the resulting topographic maps were equipped with contour lines. For irrigation systems covering a land area of about 10,000 ha or more usually based on aerial photography maps with detailed topography features.
Requirements for general topographic map making detailed as follows, namely:
Portrait land forms (landform) should have a micro relief with the obvious physical form, it will directly determine the layout and location of irrigation channels, and the discharge channel.
Accuracy land surface elevation.
In flat areas, the slope of the line should be less than 10 cm / km. Accuracy in terms of height is important as this will indicate whether a system of irrigation and drainage services (disposal) will function.
In areas that have steep land, services irrigation systems and drainage systems is highly dependent on the slope and height, according to the interval contour line with regulations, as follows:
o flatland <2% with an interval of 0.5 m
o soil choppy and ramps 2-5% with an interval of 1.0 m
o hilly 5-20% at intervals of 2.0 m
o mountainous> 20% with an interval of 5.0 m
Measurement river and weir Location
For the planning of the main building on the river required a detailed topographic information about the location of the river and weir. Together with measurements for general topographic map, must be measured anyway some point in the river. The results will be used in the preliminary planning of irrigation networks. This measurement includes the following elements:
Map section of the river where the main building will be constructed. The scale of this map is 1: 2,000 or greater covering 1 km to 1 km upstream and downstream to the main building and extends up to 250 m to each side of the river. Regional banks are observed to be everything. Measurement activities also include making maps of flood-prone areas. The map must be equipped with contour lines at intervals of 1.0 m, except in the riverbed where necessary contour lines at intervals of 0.50 m. The map should also contain important boundaries as the boundaries of villages, rice fields and all the infrastructure.
Pieces longitudinal cross section of the river with every 50 m. Long pieces lengthwise along the horizontal scale should be made the same as for a map of the river on the vertical scale of 1: 200 or 1: 500, depending on the steepness of the terrain. Scale. cross-section 1: 200 horizontal and 1: 200 vertically. Length of the cross section is 50 m to each side of the river. Elevation will be measured at a maximum distance of 25 m or 0.25 m height difference which can be achieved more quickly.
Measurement weir exact location details should be made, which resulted in a map scale of 1: 200 or 1: 500 for an area of approximately 50 ha (1000 x 500 m2). This map will show the location of all parts of the main building, including the location of sandbags and levee cover. This map will be equipped with rincik point height and contour lines every 0.25 m.