MMT findings: Poor drainage, heavy rains, other factors cause Casisang flood
MALAYBALAY CITY (BukidnonNews.Net/10 October 2021) Intense rain falling into an area with poor drainage and a host of other factors have caused the flood that hit subdivisions and adjacent areas in Brgy. Casisang on September 30, Maria Anita Fernandez, City Environment and Natural Resources Officer said, citing initial results of the Multipartite Monitoring Team of Malaybalay City’s probe on October 5.
Fernandez told BukidnonNews.Net Friday evening heavy rains in the run up and on the day itself of the flood sent excessive amount of water into an area with poor drainage and with ground that cannot hold much water due to erosion.
She said silts and debris blocked available drainage canal and culverts with portions of the area without even a canal.
Fernandez, who noted that they are yet to submit an official report, cited in the phone interview the blocked water path supposed to channel water to Mamala Creek on the side of the circumferential road where the Northern Mindanao Wellness and Reintegration Center and the city’s TESDA Isolation Facility are located.
She said rain water was instead channeled through the road leading to the subdivisions, from the TESDA Isolation Facility down to the DPWH Depot and the Department of Agrarian Reform office. In that area, she said, there is no drainage canal.
ABC President and Casisang Brgy Chair Bonifacio Valiente said everybody has a role to play to prevent the flood from happening again. The flood affected about 500 households in six of Casisang’s 25 puroks or zones. He said from higher elevation, flood water went through Purok 20, Purok 17 then Purok 19, then to Purok 22, 23 and 18. Valiente said there is a need to build a city control project as part of a larger urban plan for the city (see related story).
The Pagasa weather bureau confirmed the reported high amount of rainfall.
Engr. Ybonne Mae Gabales-Pedraza, weather specialist at PAGASA Malaybalay Station, said on September 30, they measured the amount of rainfall to be 55.2 millimeters. She said consecutive rain was already experienced in Malaybalay City days before the flood due to Intertropical Convergence Zone (ITCZ) and localized thunderstorms.
On September 20, the amount of rainfall was 17.8 mm, on September 22 it was 22.8 mm, on September 25 it was 28.4 mm and 10.2 mm on September 27. Then just two days before the flood, rainfall intensified to 62.4 mm on September 28 and 33.2 mm on September 29.
“These series of rainfall events resulted to surface runoff where the ground is so saturated that it cannot absorb the rain anymore,” she told BukidnonNews.Net.
She added that the excess liquid that flowed across the surface of the land, road and into nearby creeks caused the flood in the low-lying areas.
Based on references provided by Ms. Anianita Fortich, Senior Weather Specialist of DOST PAGASA in Northern Mindanao, rainfall from 7.5 to 15 millimeters per hour is Yellow Rainfall Advisory, which means flooding is possible in low-lying areas and near river channels. When it reaches 15 to 30 mm range it will be Orange Rainfall Advisory, which means flooding is threatening and there is alert for possible evacuation.
For rainfall above 30 mm, which should draw a Red Alert Status, serious flooding is expected in low-lying areas and there should already be evacuation. In Malaybalay City, red alert mark was already hit before the day of the flood, on Sept. 28 with 62.4 mm and on September 29 with 33.2 mm.
Fernandez said the sandy clay loam soil type in the area surrounding the subdivision, planted mostly to sugarcane and corn, could not contain that much water. Most of the agricultural land in the area, she said, were on their land preparation stage yet as of the flood event. With poor drainage in this area, she said, it did not help slow down rainwater causing the flood.
Fernandez said the shallow canal in the San Jose – Dalwangan Diversion Road also contributed to the flood. She also did not rule out the contribution to the flood of the banana plantation in the area. She said based on their previous monitoring, the plantation has complied with their commitments to their environmental compliance certificate (ECC) but the volume and speed of water after days of flood may have caused the overflow of their catchment area.
She said the MMT recommended for the plantation to conduct periodic maintenance of their soil erosion measures. She said there is a need to desilt the catchment areas and strengthen mulching. According to infonet-biovision.org, mulching is the use of plant materials or saw-dust, stones or plastic planes to spread upon the surface of the soil to help protect from erosion, among other purposes.
She also cited the need to build a canal from the TESDA facility to the DAR office. She mentioned other recommendations: to plant trees or bamboo along the national highway, for subdivision landowners to check clogged drainage, for farmland owners to also plant bamboo and trees to hold water in their areas.
Fernandez said the City Engineer’s Office, in cooperation with other offices dredged the shallow drainage and clogged canals on October 1 to prevent a repeat of the situation in case of heavy rains again. She said it did not flood in the area on October 4 and 5, when rainfall was measured to be 15 and 17 millimeters, respectively. (BukidnonNews.Net)
IN PHOTO: One of the worst hit areas of the September 30, 2021 flood in Brgy. Casisang, Malaybalay City Courtesy of CDRRMO Malaybalay