Phân tích ngưỡng mưa phát sinh một số trận lũ quét, lũ bùn đá thuộc các tỉnh Lai Châu, Điện Biên, Yên Bái, Sơn La

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Tác giả: Xuân Việt Bùi, Bá Thao Vũ

Ngôn ngữ: vie

Ký hiệu phân loại:

Thông tin xuất bản: Tạp chí Khí tượng Thủy văn, 2023

Mô tả vật lý: tr.96-110

Bộ sưu tập: Báo, Tạp chí

ID: 340818

Thêm vào giỏ Liên kết toàn văn

Cảnh báo lũ quét, lũ bùn đá dựa vào lượng mưa gặp nhiều thách thức như: trạm đo mưa ít và đặt xa khu vực tập trung nước và hình thành lũ, công nghệ dự báo mưa cho lưu vực nhỏ có địa hình chia cắt ở vùng núi còn hạn chế, ngưỡng mưa sinh lũ thay đổi theo không gian và thời gian, v.v.... Nhằm đánh giá mức độ chính xác ngưỡng mưa cảnh báo phát sinh lũ quét, lũ bùn đá, nghiên cứu này phân tích ngưỡng mưa của 16 trận mưa đã từng sinh lũ quét, lũ bùn đá thuộc các tỉnh Lai Châu, Yên Bái, Điện Biên, Sơn La và so sánh với ngưỡng mưa cảnh báo lũ quét theo quy định hiện hành của Việt Nam. Bên cạnh đó, lượng mưa tích lũy sinh lũ và không sinh lũ cũng được phân tích dựa trên số liệu của 142 trận mưa thống kê từ 6 trạm đo mưa: Tam Đường, Mường Tè, Mù Căng Chải, Văn Chấn, Tuần Giáo, Bắc Yên trong khoảng thời gian từ tháng 6 đến tháng 9 thuộc 5 năm từ 2015 đến 2019. Kết quả cho thấy, lượng mưa tích lũy sinh lũ quét, lũ bùn đá chênh lệch lớn giữa các lưu vực, biến động phổ biến trong khoảng từ 80 mm đến 240 mm, trong đó có 7/16 trận có ngưỡng thấp hơn ngưỡng cảnh báo hiện hành, tức nhỏ hơn 100 mm/24h. Rất nhiều trận mưa, 133/142 trận, có lượng mưa tích lũy lớn hơn ngưỡng mưa đã từng sinh lũ nhưng không làm phát sinh lũ quét, lũ bùn đá. Một số đề xuất nâng cao độ chính xác cảnh báo lũ quét, lũ bùn dựa vào lượng mưa cũng được trình bày trong bài báo này.Flash flood and debris flow warnings based on rainfall thresholds are challenges due to limited rain gauge stations located in the formation areas, limited technology for forecasting rainfall at narrow-scale and fragmented terrain in mountainous regions. The rainfall thresholds for flash flood warnings vary in space and time. To assess the accuracy of flash flood and debris flow warning rainfall thresholds, this study analyzes the rainfall thresholds of 16 rainfall events that have caused flash floods and debris flows in Lai Chau, Yen Bai, Dien Bien, and Son La provinces. We then compare them with the current flash flood warning thresholds in Vietnam. Also, accumulated rainfall that leads to flash flood, debris flow and non-flash flood, debris flow events is analyzed from 142 rainfall events recorded at six rain gauge stations: Tam Duong, Muong Te, Mu Cang Chai, Van Chan, Tuan Giao, and Bac Yen, collected between June and September from 2015 to 2019. The results show significant variations in accumulated rainfall leading to flash floods and debris flows among different river basins, ranging from 20 mm to 242 mm. Among the 16 events analyzed, 7 events had rainfall thresholds lower than the current warning thresholds, i.e., below 100 mm/24h. A large number of rainfall events (133 out of 142) exceeded the rainfall thresholds that had previously caused flash floods and debris flows but did not result in such events. This study also presents some proposals to enhance the accuracy of flash flood and debris flow warnings based on rainfall.

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