Modeling interactions between tides, storm surges, and river discharges in the Kapuas River delta

Abstract

Abstract. The Kapuas River delta is a unique estuary system on the western coast of the island of Borneo, Indonesia. Its hydrodynamics are driven by an interplay between storm surges, tides, and river discharges. These interactions are likely to be exacerbated by global warming, leading to more frequent compound flooding in the area. The mechanisms driving compound flooding events in the Kapuas River delta remain, however, poorly known. Here we attempt to fill this gap by assessing the interactions between river discharges, tides, and storm surges and how they can drive a compound inundation over the riverbanks, particularly within Pontianak, the main city along the Kapuas River. We simulated these interactions using the multi-scale hydrodynamic model SLIM (Second-generation Louvain-la-Neuve Ice-ocean Model). Our model correctly reproduces the Kapuas River's hydrodynamics and its interactions with tides and storm surge from the Karimata Strait. We considered several extreme-scenario test cases to evaluate the impact of tide–storm–discharge interactions on the maximum water level profile from the river mouth to the upstream part of the river. Based on the maximum water level profiles, we divide the Kapuas River's stream into three zones, i.e., the tidally dominated region (from the river mouth to about 30 km upstream), the transition region (from about 30 km to about 150 km upstream), and the river-dominated region (beyond 150 km upstream). Thus, the local water management can define proper mitigation for handling compound flooding hazards along the riverbanks by using this zoning category. The model also successfully reproduced a compound flooding event in Pontianak, which occurred on 29 December 2018. For this event, the wind-generated surge appeared to be the dominant trigger.

Tidal Flood Model Projection Using Land Subsidence Parameter in Pontianak, Indonesia

“…Pontianak is one of the cities in West Kalimantan Province, Indonesia which is often affected by tidal floods, especially in the riverbank areas (BPIW, 2017;Gultom et al, 2020). Previous studies (Kuntinah et al, 2021;Sampurno et al, 2022a;Sampurno et al, 2022b) have shown that tidal flood in Pontianak often occurs during the high tide seasons from December to February. During this period, the tides reach a maximum height because affected by Asian monsoon (Kästner et al, 2018).…”

“…According to Sampurno et al (2022a), the flood hazard along the Kapuas River is delineated into three regions. From the river mouth to 30 km upstream of the river (Pontianak) is the tidedominated area, where discharge no longer controls the maximum water level, which is correlated to flood hazards.…”

“…1). The Kapuas Kecil River has a width of about 449 -1977 meters (Lestari et al, 2017), with varying depths from 1 meter (river mouth) to 15 meters (middle stream) (Sampurno et al, 2022a). Potential inundation due to tidal flood within the city through the Kapuas River stream could reached 9.70 km 2 in Pontianak Kota and Pontianak Barat districts and 4.36 km 2 in Pontianak Selatan and Pontianak Tenggara districts (Purnomo et al, 2019;Kurnia et al, 2019).…”

“…Kuntinah et al (2021) used the DELFT3D model to simulate water levels in several flood cases. Sampurno et al (2022a) used the SLIM model to predict tide-surge-discharge interaction along the Kapuas riverbank. Therefore, this study attempts to simulate the current and the future tidal floods in Pontianak under land subsidence projection scenarios using the DELFT3D model integrated with the HEC-RAS (Hydrologic Engineering Center River Analysis System) model.…”

Integrated machine learning and GIS-based bathtub models to assess the future flood risk in the Kapuas River Delta, Indonesia

“…The water levels within the low-lying KRD are influenced by tide and wind surges from Karimata Strait, as well as the river discharges from the Kapuas and the Landak rivers (Sampurno et al 2022). The flood risk here, and in other deltas, are likely to increase in future climate (Kundzewicz et al 2014).…”