top of page
DALL·E 2024-05-14 15.43.59 - A wide aspect cover image depicting a flooded river scene, sh

RIVER PERIYAR FLOODPRONE ZONES, Kerala, INDIA

-Nashvelle Fernandes,
Student of AGSRT

SUMMARY

This GIS project report provides a comprehensive analysis of areas
prone to flooding along the Periyar River in Kerala, India. Utilizing Geographic Information System (GIS) technology, the report identifies highrisk zones, assesses vulnerability factors, and proposes mitigation
strategies.
It includes data on topography, land use, hydrology, and historical flood patterns to create accurate flood risk maps. Recommendations may include infrastructure improvements, land use planning measures, and early warning systems to minimize flood damage and enhance
community resilience.

Summary.jpg

(This Project Was Done Using Various Analyst Tools from ArcGIS Pro)

1.Introduction:

1.1 About River Periyar

Periyar, is the longest river and the river with the largest discharge potential in the Indian state of Kerala. It is one of the few perennial rivers in the region and provides drinking water for several major towns. The Periyar is of utmost significance to the economy of Kerala. It generates a significant proportion of Kerala's electrical power via the Idukki Dam and flows along a region of industrial and
commercial activity. The river also provides water for irrigation and domestic use throughout its course besides supporting a rich fishery. Kochi city, in the vicinity of the river mouth, draws its water supply from Aluva, an upstream site sufficiently free of seawater intrusion. Twenty five percent of Kerala's industries are along the banks of the Periyar. These are mostly crowded within a stretch of 5
kilometers in the Eloor-Edayar region (Udhyogamandal), about 10 kilometers north of Kochi harbor. 

1.2 Origin & Path

The Periyar has a total length of approximately 244 kilometers and a catchment area of 5,398 square kilometers, of which 5,284 square kilometers is in Kerala and 114 square kilometers is in Tamil Nadu

Origin and path.png

(Figure 1: Terrain map around River Periyar, showing its sources ifrom the Western Ghats Mountain Ranges.
Source: Nashvelle Fernandes (Author), with ArcGIS Pro.)

1.3 Sources

The source of the Periyar lies high in the Western Ghats. The state of Kerala asserted during the hearings on the Mullaperiyar issue in the Supreme Court of India that the Periyar originates in Kerala, flows entirely through Kerala and joins the sea in Kerala. This was also admitted by the state of Tamil Nadu in the court. Periyar originates at the southeastern border of Idukki district. The
source of the river lies in the remote forests of the Periyar Tiger Reserve. The river originates from Chokkampatti Mala, a peak on the southern boundary of the Periyar Tiger Reserve. 

1.4 Course

In its early course, the river flows in a narrow north sloping valley starting from the Chokkampatti hills and extending north about 25 kilometers. After flowing 48 kilometres from its origin and on reaching Mount Plateau at its eastern end, it is joined by the west flowing Mullayar, an important tributary at Mullakudy. During this journey the Periyar traverses through the Periyar Tiger Reserve,
flowing across or forming the boundaries between various sections of the reserve. Going downstream, it defines a part of the border between Periyar section of the reserve in the east and Sundaramala section in the west before reaching the Periyar Lake.


The Mullaperiyar dam is constructed at the confluence of the Periyar and Mullayar to create the Periyar Thekkady lake and reservoir, as well as the Periyar National Park. The area belonging to Tamil Nadu in the Periyar basin is located far down the river from the Mullaperiyar Dam site. This area is drained by the tributary Nirar, which is diverted to Tamil Nadu as a part of inter-state
Parambikulam-Aliyar Project (PAP) agreement.


From Periyar Thekkady lake and reservoir, some water is diverted eastwards to Tamil Nadu via a tunnel. The diverted water, after power generation, is let into the Suruliar river (a tributary of the Vaigai River) thereby resulting in an inter-basin transfer of water. Downstream of the Mullaperiyar dam, the Periyar continues to flow northwestward for 35 kilometres, exiting the Periyar Tiger
Reserve and passing through Vandiperiyar, Elappara and Ayyappancoil to the Idukki reservoir formed by the Idukki, Cheruthoni and Kulamavu dams. The Idukki dam is constructed across the Periyar river on the famous Idukki gorge formed by the Kuravan and Kurathi hills. 

The main Periyar below the Idukki reservoir flows due north parallel to the western edge of the Idukki plateau and is joined by the Perinjakutty from the east and Muthirapuzha from the north. After the confluence with Muthirapuzha, the river flows northwestwards and enters Ernakulam district at Neriamangalam. It is joined by its major tributary, the Idamalayar, 1.5 kilometers upstream
of the Bhoothathankettu barrage. After receiving the waters of the Idamalayar river, the Periyar flows west along the midlands of Ernakulam district. At Aluva, the river bifurcates into the Marthandavarma and the Mangalapuzha branches. The
Mangalapuzha branch joins Chalakudy River and empties into the Lakshadweep Sea at Munambam, and the Marthandavarma branch flows southwards, again dividing into two near Kunjunnikkara island, going through the Udhyogamandal area and finally draining into the Cochin backwater system (part of Vembanad Lake) at Varappuzha. The Vembanad backwaters are connected to the Lakshadweep Sea at Cochin and Kodungallur.

2.METHODOLOGY:

Creating a flood zone map in ArcGIS Pro involves several steps:

a) Deriving Hydrology from Digital Elevation Model (DEM):

  • Obtain a Digital Elevation Model (DEM) from sources like the United States Geological Survey (USGS)

  • In ArcGIS Pro: Import the DEM onto the map canvas. Use the “Fill” tool to fill sinks and depressions in the DEM.

  • Calculate flow direction and flow accumulation from the filled DEM.

  • Determine stream order based on flow accumulation. (These hydrological features help identify potential flood-prone areas)

b) Deriving Slope from DEM:

  • Calculate the slope of the terrain using the DEM.

  • Steeper slopes are more susceptible to rapid runoff during heavy rainfall, increasing flood risk.

c) Accessing and Importing Land Cover Data:

  • Obtain land cover data (such as the National Land Cover Database).

  • Import the land cover data into ArcGIS Pro.

  • Classify land cover types (e.g., urban, forest, water bodies) to assess their influence on flood susceptibility.

d) Visualization and Interpretation:

  • Symbolize the flood susceptibility map to highlight areas at risk.

  • Interpret the results, considering the combined influence of all factors.

  • Share the map with stakeholders, emergency management agencies, and urban planners.

  • Remember that flood susceptibility analysis is a complex process, and local context matters.

  • Adjust the methodology based on the specific study area and available data.

3.GIS ANALYSIS RESULTS:

3.1 Extent of River Periyar

Periyar river at Bhoothathankettu near Kothamangalam, Ernakulam. The Periyar has a total length of approximately 244 kilometers and a catchment area of 5,398 square kilometers, of which 5,284 square kilometers is in Kerala and 114 square kilometers is in Tamil Nadu.

Extent of River periyar.png

Figure 2: River Periyar 3D Depiction, showing it origin from the Western Ghats Mountain Ranges and passing through the plains of Kerala before draining into the Arabian Sea. 

3.2 Basins & Streams Around River Periyar

This river basin is the second largest basin of Kerala State with a drainage area of 5398 sq. km. of which 114 sq. km. in the Anamalai fold lies in the State of Tamil Nadu. The Periyar Basin lies between 090 15' N to 100 20' N and longitude 760 10' E to 770 30'E.


               Further down, it is joined by six tributaries after which the important tributary Edamala joins the Periyar. Passing Malayattur and there after taking a meandering course, the river reaches Alwaye where it divides itself into two branches. Muthirapuzha River, Mullayar River, Cheruthoni River are the few major tributaries of the Periyar river.

Basins & Streams Around River Periyar 1.png

River Periyar Intersecting Basins.

Basins & Streams Around River Periyar 2.png

 Stream in Periyar Basin.

3.3 River Periyar Induced Flood Zones

The Periyar is the longest river in Kerala and has the highest discharge potential. The major dams across this river that are maintained by the KSEB are Idukki, Lower Periyar, and Madupetty. The primary regions under built-up facing the flood include the talukas of Aluva, Paravoor, Kodungalloor, Perumbavoor and Kothamangalam taluk of Ernakulam district with Irrinjalakuda of Thrissur district.

induced flood zones.png

 River Periyar Induced Flood Zones

4.CONCLUSION

THE STATE OF KERALA HAS AN AVERAGE ANNUAL RAINFALL OF ABOUT 3000 MM. RAINFALL IN THE STATE IS
CONTROLLED BY SOUTHWEST AND NORTHEAST MONSOONS. ABOUT 90% OF THE RAINFALL OCCURS DURING THE SIX
MONSOON MONTHS. HIGH INTENSITY STORMS PREVALENT DURING THE MONSOON MONTHS RESULT IN HEAVY FLOWS IN ALL RIVERS. THE CONTINUOUS AND ABUNDANT RAINFALL THAT OCCURS IN THE STEEP AND UNDULATING TERRAIN REACHES THE MAIN RIVERS THROUGH INNUMERABLE STREAMS AND WATERCOURSES.

FLOOD HAPPENS WHEN A DAM BREAKS AND IT IS VERY LETHAL. DAMS MUST BE BUILT WHEREVER IT IS NECESSARY AND ALSO IT IS EQUALLY IMPORTANT TO MAINTAIN THOSE DAMS, IN ORDER TO PREVENT FLOODS. TO CONCLUDE, WE CAN NEVER PREVENT A NATURAL DISASTER FROM HAPPENING ALL OF A SUDDEN. FLOOD IS A SERIOUS ISSUE WHEN IT COMES.

5. References

  • THE STATE OF KERALA HAS AN AVERAGE ANNUAL RAINFALL OF ABOUT 3000 MM. RAINFALL IN THE STATE IS UNACADEMY.COM/CONTENT/SSC/STUDY-MATERIAL/GENERALAWARENESS/ORIGIN-OF-PERIYAR-RIVER
    • INDIAWRIS.GOV.IN › WIKI › DOKU › ID=PERIYAR
    • HTTPS://ENVIRONMENTCLEARANCE.NIC.IN › ONLINE › TOR
    • HTTPS://PAPERS.SSRN.COM › SOL3 › DELIVERY.CFM

bottom of page